The Spirit and Opportunity landing sites as former Martian Poles

Abstract:

Mars has many enigmatic features, such as Tharsis, Olympus Mons, Valles Marineris, and Alba Patera. The volcanoes and Valles Marineris are huge compared to the size of Mars with no apparent explanation for what made them. In the theory outlined here the poles of Mars wandered through history in response to 4 major impacts, Utopia, Isidis, Argyre, and Hellas. As each impact occurred the large negative mass of the crater tended to attract a rotational pole to it, and then later as large volcanoes formed the mass of these tended to move to the Equator. The combination of these events caused the poles to move over much of Mars spreading water and ice signs along its path, and often leaving the rest of Mars dry by comparison. This would account for how Mars shows so many water and ice signs in some areas and appears so dry chemically in others. In this paper only part of the polar path is shown, from south of Valles Marineris the pole moved to Meridiani Planum where the Opportunity rover is now. The opposite pole, which eventually became the current North Pole moved from the area of the Isidis Crater to the area around Gusev where the Spirit Rover is. We show how these areas are geologically consistent with former poles, and how this polar path implies a watery zone, possibly habitable for hundreds of millions of years. This would be sufficient for life to possibly evolve substantially if it existed at this time.

 

Keywords: astrobiology, crinoid, Gusev, Mars, Meridiani,, Opportunity, polar, Spirit, water.

 

This theory originally came about from reading a paper by Sprenke and Baker[1] on a proposed polar wander path on Mars. In the process of examining this we accumulated published papers referring to features along this path, and looked at whether features there were consistent with having been on a pole.

 

 Typically such features would be formed by water or ice, and the terrain would be similar to known geology we see on the current poles. This was contrasted with areas off this polar path, which typically were much drier and ice free. Because the proposed polar path went back to before Tharsis, Olympus Mons and Valles Marineris it became possible this path was directed by the same forces that made these formations, and much of the current Martian landscape. We found that virtually every single paper published on Martian geology is consistent with this polar wander path.

 

Because these large volcanoes have so much mass they tend to move to the Equator, and so these could only form at certain times in the polar wander. The polar path if correct then implies when these Mons formed and also when large craters formed as their negative mass would tend to attract the pole to them. Once the correct polar path is known, then every other Martian feature with a significant impact on the gravitational balance of Mars should only occur at certain points along that path.

 

Because of space limitations and the serendipitous landing of the Rovers on two former poles opposite each other, we have reproduced here the middle part of the polar path. In the next paper we will show the possible events before this section that formed Tharsis Montes, Olympus Mons, Elysium Mons, and Valles Marineris. A following paper will carry on after this one, with the Hellas impact attenuating the Martian magnetic field and moving the pole to Hellas Crater, and then its current position.

 

While it is not known if life exists on Mars the polar path strongly implies a habitable zone existed around these poles as they wandered across Mars, for hundreds of millions of years or more. The large volcanoes of Tharsis, Elysium Mons, and Elysium Mons may have heated the planet, as they are associated with parts of the polar path that appeared to generate huge amounts of water.

 

In the three papers we will refer to 5 pole positions as being stable for a time, and the polar movement between these positions. The current pole positions we call Pole 5, and the polar movement from Pole 2 to Pole 3 is discussed here, Pole 4 is near Hellas Crater. To follow this path a good map of Mars is essential as many of the names are obscure. If you Google and download “mola_regional.pdf”[2] this map shows all the place names referred to here. For any image numbers, placing the image number in a search engine and selecting the link from msss.com is the fastest way to find them.

 

In this paper we concentrate on the movement from what we call the South Polar Cap 2 position near Solis Planum (south of Valles Marineris) to South Polar Cap 3 position at Meridiani Planum, shown in Figure 1. The associated North Pole moved from the North Polar Cap 2 position around Isidis Planitia eastward to near Lucus Planum as the corresponding North Polar Cap 3. We call this North Polar Cap 3 because eventually it will go to the current North Pole position. In this theory the Argyre impact starts the polar wander from the second to the third position.

 

The path begins when the Pole is moving eastwards from the South Polar Cap 2 position around Solis Planum, to north of Argyre Basin into Margaritifer Terra and then east to Meridiani Planum, the site of South Polar Cap 3. One should remember that a pole is very large in its influence, so the exact position of the centre is often not significant. For example the current poles are quite asymmetric in shape compared to the rotational pole itself.

 

There is no direct evidence for the Polar Cap stabilizing or remaining in Margaritifer Sinus for any great length in time along this route. Figure 1 shows this path, South Polar Cap 2 to 3 is from Solis Planum to Meridiani Planum.

 

 

Figure 1: The proposed polar wander path from Pole 2 to 3.

 

The large river networks in the Xanthe Terra and Margaritifer Sinus areas imply the atmosphere at the time was much thicker, since water would need a much higher air pressure than found today.  A higher polar obliquity may have also contributed to this. The axial tilt of Mars is believed to change periodically over time, and when the angle is greater the ice around the poles is thought to melt or sublimate much more.

 

This gives a possible habitable environment at this time, with abundant water, heat from the Argyre impact, and higher air pressure. These water signs persist all the way along the polar path to Meridiani Planum. 

 

According to Grant[3] Margaritifer Sinus contains remnant high valley densities, which is consistent with a moving pole and ice melting. This area was resurfaced several times[4], perhaps from the subsequent volcanism related to the Argyre impact. Therefore, ice may have partially vaporized, sublimed or melted, either due to impacts, and/or due to subsurface heat from associated geothermal activity. While Grant[5] believes some precipitation occurred, most ground water would be consistent with a water table associated with either a forming or sublimation/melting of an existing pole. The Parana Valles[6] drainage system is particularly extensive. Therefore, according to Grant[7], groundwater discharge[8] must have continued for some considerable time. The length of time referred to would likely be sufficient for life, if present to evolve substantially.

 

Lewis and Aharonson[9] examine Holden Crater and the distributary fan discovered in it. This area is near Argyre Crater and implies liquid water was discharged from the Polar Cap nearby. Pondrelli et al[10] also examine the area and how it connects the Argyre Basin to the northern channels. Williams et al[11] report on fans in Xanthe Terra, along the path of the Polar Cap.

 

Hynek et al[12] suggest that the fluvial resurfacing in this area lasted for a period of some several hundred million years. A combination of rainfall and sapping[13] appear likely, so lakes may well have formed[14]. Polar wander may link the two main theories of precipitation and sapping, hence explaining the extensive valley networks[15].

 

According to Nelson ice may have periodically melted. An examination of Margaritifer Sinus, by Philips et al[16] concluded that much of the Tharsis bulge was already in place before the drainage channels formed. This is consistent with the general rise in elevation in the area of Tharsis and Sinai Planum from the Argyre impact. At this time Tharsis and Olympus Mons would have been growing after the Argyre impact, and their extra weight would tend to move to the Equator. This would have the effect of forcing South polar Cap 3 to move eastwards to Meridiani Planum. This part of the polar path (and its antipodes, the future North Pole) shows abundant evidence of water and ice. The area around Margaritifer Sinus was plausibly a habitable zone and the Rover Opportunity has now shown Meridiani Planum was a habitable zone. In between these two there are enough water signs to imply this was a long period of Martian history in which a habitable zone existed. It is not known however if there was life there to take advantage of this.

 

During the late Noachian, Tharsis Rise was large enough to direct the channels northward. Large amounts of material eroded from this area were transported along these channels, most probably as a direct result of basal water erosion during  melting (and sublimation) as the Pole moved north east of Valles Marineris[17] [18] towards Margaritifer Sinus.

 

By the time the Polar Cap had moved north east of Valles Marineris water and ice would have accumulated in it as the Polar Cap melted and moved from the Argyre impact event, which may explain the paleolakes[19] there. Carr[20] suggested that ground water flowed into Valles Marineris and then into Chryse Planitia, forming lakes. Rossi et al[21] believe there is good evidence of ice and glaciation, consistent with a polar area adjacent to and south of the Valles Marineris at that time. Glacial features in the area support this interpretation.

 

Lunae Planum would also have received water from the moving and melting of the pole. Shalbatana Valles originates in the chaos on Lunae Planum (Greeley and Kuzmin[22]). Interestingly this would have resulted from a probable impact basin that formed a catastrophic outflow.

 

Nelson and Greeley[23] discuss three major fluvial events in Xanthe Terra, with indications of surface water flow. The first is a broad sheetwash from the Valles Marineris area, perhaps coinciding with the Argyre impact. Following this more extensive flooding occurred, forming Shalbatana, Ravi, Simud, Tiu, and Areas Valles. This may coincide with the pole migrating to Margaritifer Sinus. The majority of surface water was sourced from chaos areas[24]. This gives a direct link to the Argyre area and perhaps to that impact.

As we follow the polar wander, the fluvial-features seem to overprint other terrain, so flooding may have continued as the Polar Cap migrated.

 

At the antipodes North Polar Cap 2 near the growing Elysium Mons started to move eastward. This area has many signs of ice and water, for example M0901921, M0905888, M0906366, M1001498, M1900226, M1902068, M2000840, and M2000907. Again these photos from the MOC can be seen by placing the image numbers in a search engine and selecting the link from msss.com. Further signs can be seen in Martei Valles in M2001192, M2200885, and SP238804. Lanagan et al[25] see evidence of fluvial flows associated with Elysium Mons and lava flows in the area, and rootless cones[26] also indicate ice in the area.

 

The new Odyssey results of subsurface ice[27] indicate a large deposit on the equator in Babaea Terra. A second area of ice occurs on the left edge of the map, just below the equator. This corresponds to the location of the opposite North Polar Cap 3. According to Sprenke et al the South Polar Cap moved in a curve to 0S 330W, almost into the centre of the ice rich area at Meridiani Planum. We call this area South Polar Cap 3. The geology and the geophysical data indicate icy areas on opposite sides of the planet. When we calculate the radius of the planet and adjust for any faulting, the result suggests that these areas were almost certainly a polar pair. For each Polar Cap pair we back-calculated the polar separations. The differences in diameters are almost perfectly offset by the thickness of rift-like valleys and fault movement and by assuming earth-like passive fault movement the polar age relationships could be back calculated.

 

We believe the poles stabilised in these ice rich areas for a long time, also with ample evidence of water signs. Thus the possible habitable zone extends to the results we see from the Rovers and implies similar chemistry and water signs may be found along this whole polar path from Solis Planum.

 

Rift-like faults, glaciation, evidence of surface water, and even volcanic activity tend to track the polar movement. The movement of Pole 2 to Pole 3 adds to approximately 150 degrees of longitudinal movement so this is consistent with Tharsis forming near South Polar Cap 2 and then moving nearly 180 degrees to the Equator, which pushed the poles about 150 degrees eastward.

 

In this time Tharsis had to be growing so it would have been adding a lot of heat to the atmosphere, and initially along with the newly formed Argyre Crater parts of South Polar Cap 2 would have overlaid these hot areas, melting water and CO2 if frozen. This would thicken the atmosphere and perhaps create snow or precipitation away from the heat. Tharsis and Argyre, with Elysium Mons then could have supplied the heat for this potentially habitable zone to last so long. This would also explain why Mars has so many water signs when it should have been too cold for most of its history. The overall temperature of Mars probably remained low, inhibiting the destruction of olivine even in the presence of water.

 

South Polar Cap 3 assumed a position between the Argyre and Isidis impact basins as each, being low gravity (low mass) would tend to be close to this pole.  When this occurred the Pole 3 positions would attain a stable configuration. Tharsis was by this time near the Equator and South Polar Cap 3 was near the two main negative masses of the Argyre Crater and Isidis Crater, with Utopia Crater a lesser influence.

 

Interestingly, South Pole 3 coincides with an area of heavy Noachian cratering[28] and the second cratered area corresponds well with the opposite North Pole 3. One likely explanation is that the polar ice protected the craters from erosion, and when they were exhumed from the ice they remained in more pristine condition. Pole 3 seems to have been stable for a long enough time for crater disparity. It also implies at this time that the surface was being altered severely and other craters were being buried or obliterated by lava flows.

 

Volcanism seems to follow the polar wander, so is either related to the shock waves from impacts or is a late stage effect, occurring in relation to degassing (geothermal activity) during faulting of polar valleys. This would explain how volcanoes have apparently restarted in Martian history and the surface is relatively young in parts.

 

Rift-like, passive, or strike-slip valleys would be thus be overprinted by basal melting of icecaps and related sublimation. Most large catastrophic flood (outburst) features occur adjacent to these poles so may be triggered by increased geothermal heat. Pole 3 likely remained in a stable location through this resurfacing.

 

These crater areas are linked into what is termed the Noachian age. Thus, after the Argyre impact may be regarded as the Hesperian, obliterating much of the Noachian terrain except for these parts protected with polar ice. Some other areas with Noachian craters are also found around Margaritifer Sinus, implying the Polar Cap may have slowly moved and protected other areas for a time in its path. In a later paper we will show a large northern ice sheet or ocean would have sublimated after the Hellas impact, exposing the terrain referred to as Amazonian. The two impacts then may have caused the features known as Hesperian and Amazonian to form. This makes it difficult to estimates times for these events as the polar path would have obscured and altered crater counts.

 

In moving from Pole 2 to Pole 3, the polar ice closely follows and may have formed or modified the dichotomy boundary. The main dichotomy boundary is seen between 180 degrees west and 90 degrees west, which is 270 degrees or ¾ of a total possible boundary. The rest is taken up by the land mass of Tharsis Montes, Syria Planum, etc.

 

South Polar Cap 2 moved from 12.7S 92.6W eastward to around 0S 330W, which is approximately 122 degrees of longitudinal movement or approximately 1/3 of the total great circle. The opposite pole migrated from 12.7N 272.6W to 0S 150W, which is where the dichotomy boundary ends against Olympus Mons, for a movement of 122 degrees. This makes 244 degrees of movement over a dichotomy boundary of 270 degrees as a polar wander path. The rest can be explained by the width of the edge of South Polar Cap 3 at 330W in Meridiani Planum, which makes it appear to extend further east. Thus virtually the entire visible dichotomy boundary falls on the same line as the movement of Pole 2 to Pole 3.

 

The Northern Lowlands represents a paradox. It is so large a negative mass that it would likely prevent the Polar Caps moving along the path proposed by Sprenke and Baker. Smith and Zuber[29] say that Hellas Crater for example is only 10% of the volume of the Northern plains. Thus its gravitational influence would be greater than either Argyre or Hellas.

 

Therefore if this polar path is correct the Northern Lowlands was partially covered in water or ice early in Martian history, neutralising its negative mass. Oner et al[30] make some estimates of its size. This would make the planet more balanced and not impede polar wander. Indeed this ice or ocean had to exist for this polar wander to occur, so proving polar wander proves the northern ice sheet existed. The Northern Lowlands is so large a negative mass that the poles could never have moved from their current position without water or ice to fill in the low areas. Hence polar wander implies this water or ice existed, and the shape of the ice rich areas at 60N shown by THEMIS implies at least parts contained more ice at some point.

 

Early in the history of Mars the Northern Lowlands may have had other impacts such as a Borealis impact lowering this area. Water and ice just as on Earth would have migrated to the lower areas balancing the planet. Over time the water would have smoothed out these ancient craters, as it may have also done with Utopia Crater.

 

The polar wander path along the dichotomy boundary may have been on a pre existing slope, altering its shape with ice and water erosion. A Polar Cap moving on a slope like this would tend to have a runoff of water heading north, accounting for the smoother surfaces in Acidalia, Arcadis, Amazonis, and Elysium Planitia.

 

THEMIS[31] shows some evidence of such a runoff. Blue ice rich areas extend from the polar path south west of Elysium Mons and north to a huge ice deposit encircling the planet at 60N. This may have been part of the ancient northern ice sheet or ocean. The heat from Elysium Mons here would have been melting part of the moving polar cap and the water flowed north to the main ocean or ice sheet. This THEMIS map should be looked at in conjunction with the previously mentioned mola_regional.pdf.

 

Figure 2 shows a map of these ice rich areas. To make them clearer in monochrome we have made the blue areas on the original appear white.

 

A is the approximate position of North polar Cap 2, where white ice deposits can be seen. This trail moves to the right down to C, and on the left edge of the map at J which would be North Polar Cap 3. North east of A there is a trail of ice (more clear in the original map) shown by B. This connects to the large ice deposit at H. In the center of the ice trail at B is Elysium Mons. This implies that the heat from Elysium Mons melted water here to make the runoff to H, and therefore that Elysium Mons was hot when the pole was at A. On the northern end of this trail is where Viking 2 landed, and also the best example of Martian spider ravines[32] [33]outside of the current South Pole. The large ice deposit at South Polar Cap 3 in Meridiani Planum is shown at I, and F an ice trail linking it to a northern ice sheet.

 

This is consistent with the motion of the pole described here. At E we see a large ice trail again, this time next to Olympus Mons and also east towards Pavonis Mons[34]. This implies some of the ice of North polar Cap 3 was melted by Olympus Mons and moved north to the large ice area at G. E is also the location of Amazonis and Arcadia Planitia which show signs of having been made smooth by water[35]. Photos M1900946 and M1901546 show many volcanoes. These probably formed partially or wholly in water. While this water may have come from melting ice it may indicate the area was covered with ice or water. Olympus Mons and Tharsis would have been still hot at this time, which helps to date these events.

Figure 3: the Northern lowlands

 

Figure 3 shows dark areas on the Martian surface around the area of H in Figure 2. This implies these dark areas may be associated with higher amounts of ice. The trails of ice leading to these dark areas imply there was liquid water, which implies some parts may have been a liquid ocean at this time.

Figure 4: Amazonis and Arcadia Planitia.

Figure 4 shows the dark areas coinciding with Amazonis and Arcadia Planitia.

 

Figure 5: Map of Martian Iron at mid-latitudes.

In Figure 5 a map of Iron on mars from the Odyssey Gamma Ray Spectrometer[36] is shown. Here we have made the red, high iron areas on the original map black to be seen more clearly. E corresponds to Amazonis Planitia as a high Iron area. This is also associated with darker soil, has many water and ice signs, and is associated with the ice trail going northwards. So it is likely then some of the Iron may have been leached from the ground by water melted by Olympus Mons from North polar Cap 2. G shows the northern ice sheet is also Iron rich and connected by water or ice trails.

F shows an iron rich area coinciding with an ice rich area. Between K and B there is a trail of Iron from Meridiani Planum, or South polar Cap 3 up to Elysium Mons. This implies again that water from the pole moved north and north east to the large ice areas at H. C shows a large Iron deposit at North polar Cap 3.

 

It would be difficult for this Iron to occur in these areas due to glaciation alone, so it is likely has some association with water. This then implies a long-term northern ocean and ice sheet at the time Olympus Mons, with heat provided along the major north-south faults by Elysium and other Mons, at the same time the Pole moved from Position 2 to 3. The Opportunity area also has high iron (Fe). We know this is due to pisolite. Hence, pisolite may have formed in at least some of these regions.

 

As the Polar Cap moved along the dichotomy boundary from 2 to 3, new ice would tend to form on the ground ahead and melt on the ground behind it as the temperatures changed. The ice in front would tend to freeze into the soil and create a similar situation to the current Pole 5 where approximately half or more of the soil is ice. When this eventually melted or sublimated the soil in the ice should have moved down the slope and spread out. If there was a high enough air pressure this should have created a seasonal water flow into Acidalia Planitia and created the smooth surface. Amazonis Planitia is thought to be flat from sedimentation or fluvial processes according to Head[37]. Fuller et al[38] believe the Alba Patera area was resurfaced volcanically and with fluvial sediments. A periodically higher obliquity may have also created a water flow.

 

There are visible water channels in Lunae Planum, Xanthe Terra, and Margaritifer Sinus, but these became less common as the Polar Cap moved eastwards. The edges of the (green) elevation in MOLA maps[39] along this path may indicate the edges of the permanent ice cap cutting a flat platform. The primary erosion may have been caused by ice. Thus, at this stage Martian temperatures and air pressure were possibly dropping after the Argyre impact.

 

The ice deposit at South Polar Cap 3 abuts a cliff to the north, which is an extension of the dichotomy boundary. This ice then implies that it is connected to the creation of this cliff and by extension created the cliff of the dichotomy boundary as the Polar Cap moved. As water ran down the slope at South Pole 3 it would have eroded the ground, but where the ground was permanently frozen the ground would have been protected. This should then give a boundary to the north of the moving Polar Cap where the ground slopes more. Note also how South Polar Cap 3 also has an ice path at approximately 345W connecting to the northern ice sheet or ocean. Water and ice signs can be seen in narrow angle images from Malin Space Science Systems, such as E0101857, E0300317, E0401351, E0401589, E0503396, E1600085, E1801705, E2001051, E2100663, and  E2301402.

 

These ice paths imply the terrain at the time was conducive for water to flow into the ice rich areas at 60N, which implies these ice rich areas were formed substantially from water runoff themselves. If they were solely formed from ice deposition there would be no need for them to connect in apparent water paths. Much of this water may have moved in subsurface aquifers, which would explain a lack of rivers connecting to the ice rich area. Much of the water or ice had to previously exist there for polar wander to occur. This can easily be tested by simulating different depths of ice to these lower areas, and seeing if it balances the planet sufficiently for the polar path shown here to occur.

North Polar Cap 3 includes the area around Gusev Crater and the Spirit Rover site. Pablo et al[40] examined Atlantis Basin on this previous Polar Cap and believe this contained an ancient paleolake. This is consistent with the idea of a Polar Cap here, the area becoming desiccated when the Polar Cap moved on. The heat sources may have been from Olympus Mons, which would have been active at the time from the Argyre impact. Spirit has found indications of repeated exposure to water[41] [42]as well as more hematite concretions.

 

Irwin et al[43] describe Ma’adim Vallis as one of the largest valleys on Mars, believed to have been carved from a large flood. This amount of water on North Polar Cap 3 fits in well with the water signs at South Polar Cap 3. Water from North polar Cap 3 may have moved northwards into Arcadia Planitia.

 

Thomas-Keptra et al[44] propose carbonate disks in ALH84001 may have formed in an area similar to conditions found by the Rover Opportunity, which would link possible life signs to these former poles.

 

This is also consistent with the idea of the water at the Rover Opportunity site being from polar ice. Leask et al[45] examine the Ravi Vallis and Aromatum Chaos areas and calculate the amount of water that would have been involved. This would be the western edge of South Polar Cap 3 and also represent an area the Polar Cap moved over.

 

Coleman[46] also examined this area and believes an ice covered lake in Ganges Chasma recharged the aquifer source. This is also consistent with the ice and water coming from South Polar Cap 3. Woodworth-Lynas and Guigne[47] examine the Kasei Valles area and believe water here was covered by ice floes. This is on the western edge of South Polar Cap 3 and again implies large amounts of water connected with the areas examined by Opportunity. The results of Holden Crater, Aromatum Chaos and Kasei Valles imply the climate was warmer at one stage for South Polar Cap 3, perhaps from increased obliquity[48].

 

Barlow and Dohm[49] examine Arabia Terra which is also on the edge of South Polar Cap 3 and conclude a subsurface reservoir of ice and liquid water existed here. Dohm et al[50] also indicate the magnetic field may have been waning, consistent with the idea of the Hellas impact later attenuating the magnetic field of Mars.

 

Arkani-Hamed and Boutin[51] plotted magnetic poles which agree reasonably well with the movement of the Polar Cap along the dichotomy boundary. The movement is roughly cycloidal, and from this it may be possible to calculate how long it took the Polar Cap to move from South Polar Cap 2 to 3. This assumes the magnetic Polar Cap may tend to move around a given rotational Polar Cap position.

 

South Polar Cap 3  contains an area called the “Arabian Water-Rich Spot” with 16% water (Mitrofanov et al[52]). Dalton et al[53] also found evidence of water accumulation in the Flaugergues drainage divide, which is also on South Polar Cap 3.

 

In each case, rift-like fault systems and hence lakes were all adjacent to old polar caps. The valleys were then modified due to sublimation of the icecaps and fluvial activity obscuring much of the faulting (as with Chasma Australe).

 

If the degassing has a volcanic relationship as implied by the polar-fault relationships, then SO2 may the major gas released with the CO2 component being minor, related only to initial defrosting. This seasonal defrosting would open pathways allowing degassing to occur.

 

The high iron and the sulfur content would thus result from volcanic degassing. The Opportunity area is bounded by rift-like faults both sides, and these look like they controlled the lake. The same Fe and Sulfur relationships occur at Viking 2 (Utopia Planitia). In each case, rift-fault systems and hence lakes were all adjacent to old polar caps.

 

In the Opportunity region, the pisolites (blue berries) form in two ways. The first is by in situ replacement, possibly of titanium-rich minerals by a lateralization-like process due to surface water. Other pisolite overlay the Opportunity lake sediments. This may have formed by shedding from an old iron deposit or may have formed like a bog iron ore, after the polar cap moved. There is strong evidence[54] at Opportunity that Meridiani Planum was wet and hospitable for life. The water would likely be from the polar cap and implying an environment hospitable to life along the whole polar path.

 

Siltstones may have formed in lakes and oceans adjacent to polar caps. Some of these may have been carbonate rich (perhaps varves) at the time. Thus, the icecap formed, then the rift valleys formed, degassing and volcanism followed. The lakes may have existed in equilibrium with the icecaps so a stable hydrological system must have existed, at least near this polar pair.

 

Many of the rifts and major normal and strike slip faults of mars occur adjacent to the polar caps. Thus, the crust has preferentially fractured in polar regions. Degassing would occur due to increased geothermal activity near hot spots or fractures in the mars crust.

 

The gases given off would be: CH4, SO2, SO3, CO, CO2, H2O.

Some of the minerals formed due to hydrothermal activity would be: FeS, CuFeS, CuSO4.

SO2 + 2H2O => H2SO4 + H2

 

H2SO4 (sulfur) + CaCO3 (Limestone/calcium-rich silts) => CaSO4 (gypsum) + H2O + CO2  

The rocks at the Opportunity site indicate that the water then eroded the gypsum crystals. The pisolites overlay the lake sediments, and either formed during or most probably after the degassing event . The gypsum in the lake sediment must therefore either be due to the lakes/oceans drying up, or since the crystals crosscut the bedding may well even be related to the degassing.  

 

CaSO4 (gypsum) + SiO2 + H2O => Mud

 

In arctic conditions mud may not always form. The result may be very fine silt, which would mix with or cover any near surface ice. If the temperature were to increase the ice just below the surface melt and the material would flow to create the mud-like surface features we see at Opportunity. Even olivine would erode to fine dust particles. In addition, any original pyrite related to hydrothermal activity would eventually weather due to the existence of water.

2FeS (pyrite) +  3H2O =>   Fe2O3 (pisolite) + 2H2S (rotten egg gas) + 1/2H2           

 

The water would most likely then react to form sulfates or revert to ice and be covered by or mixed with dust.

 

Astrobiology

 

It has been openly speculated at the recent Rover Press Conferences about fossils[55] possibly being found at the Rover sites, particularly at Meridiani. Also there have been some objects found which some believe look like fossils. We will then examine the astrobiological implications of this polar path.

 

The polar movement from Pole 2 to pole 3 as shown is accompanied by regular discharges or water, flooding, and hematite deposits. Hematite[56] has been found in the area of Pole 3, which is consistent with the having water around a polar area. The area is believed to have been recently exhumed, by Lane et al[57] which is consistent with the Polar Cap moving and exposing this area. According to Hynek Aram Chaos and Valles Marineris[58] [59] also have hematite deposits, which is consistent with the path of the moving Polar Cap from South Polar Cap 2 to 3 giving water to create hematite. Hematite has been found by Spirit at Gusev Crater on North Polar Cap 3. Catling and McKay[60] discuss possible biological aspects of hematite deposits. Cockell[61] shows that life could survive under snow, which would protect from UV rays and still allow photosynthesis.

 

Hynek et al[62] say the erosion from water in Margaritifer Sinus lasted up to several hundred million years. If the whole polar wander path from Margaritifer Sinus to Meridiani Planum lasted only this long then it implies a habitable area may then have existed on Mars for long enough for life forms to have evolved in comparable time scales and environments as on Earth. Even in Margaritifer Sinus it may have been wet enough for long enough for life to evolve substantially. Life could have stayed close enough to the volcanoes for warmth, and the polar path implies at least Tharsis was hot for several hundred million years or more.

 

Opportunity[63] has found a volcanic rock almost identical spectrographically to the Shergotty meteorite found on Earth. If transfers of material were happening when Meridiani was a pole then it implies life from Earth (or vice versa) may have been introduced by the same mechanism along this polar wander path.

 

Several objects in particular seen at the Opportunity site seem to have a resemblance to fossil shapes, such as crinoids. The fossil shapes  may be also explained by vughs forming during lateritization - but since even skeptics agree they look like fossils, more
work is required to test this hypothesis.

 

Ausich et al[64] in their Figure 5 shows some shapes which can be compared to Figures 6 and 7 in this paper. Aronson and Blake[65] show similar shapes in Polychaetes. Radwanska and Radwanski[66] show more similar examples.

 

Figure 6[67]:

 

 

Figure 7[68]: The top of the fossil like shape appears to be beginning to branch in two. There appears to also be a tail like shape.

 

Schelble et al[69] discuss biological material often found associated with hematite, similar to shapes seen by the Opportunity Rover. Figure 8[70] shows a tubular shape reminiscent of a fossil or cryptobiotic soil crusts.

 

 

Figure 8

 

Krasnopolsky et al[71] have detected methane in the Martian atmosphere which they believe is coming from the equatorial regions, which is consistent with this polar wander path. Vittorio Formisano[72] has also found methane, at 10.5 parts per billion. Mumma et al[73] also found methane. On Earth methane is usually associated with biological activity.

 

Conclusions

 

Geology along the polar path suggested by Sprenke and Baker is consistent with polar ice and water. This section of the polar path would have been initiated by the rise of Tharsis, and as Tharsis moved to the Equator it forced the eventual South Pole eastward from Solis Planum to Meridiani Planum.

 

Signs of water, ice erosion, and hematite follow the polar wander path. Since the Opportunity Rover detected a potentially habitable environment, this may have persisted during the entire polar wander from Solis Planum and perhaps even earlier.

 

Estimates of the time taken to make this polar path are consistent with the time needed for substantial evolution to have taken place in Earth’s early history. If life existed on Mars at the start of this path, then it is possible a habitable zone existed for most of not all of this time.

 

Earlier than this an ice sheet and ocean would have occupied parts of the Northern Lowlands, in a shape consistent with water flows from the heat around Olympus Mons and Elysium Mons. Water near the heat from these volcanoes would be another potentially habitable zone for as long as they supplied a heat source.

 

Objects have been found at the Opportunity site with shapes similar to fossils. Methane emissions from the equatorial regions could be signs of past or present life. The polar wander path links a large volume of geological data suggesting that liquid water and the prerequisites for life did exist on Mars and over a substantial period in time. Thus, if life is not detected it may be a function of the measurement methods used rather than life not having existed. Future missions to mars need to be designed to help answer this more substantively.

 

 

 



[1] K. F. Sprenke and L. L. Baker (2000)  “POLAR WANDERING ON MARS?” LPSC XXXI 1930.pdf

[3] J. A. Grant (2001) “Valley Evolution in Margaritifer Sinus, Mars” LPSC  XXXII 1226.pdf.

Introduction: The Margaritifer Sinus region of Mars preserves some of the highest valley network densities on the planet [1-4]. Two large northwest draining valley systems, Samara and Parana-Loire Valles, whose associated basins cover an area exceeding 540,000 km2, dominate regional drainage. These valley systems converge on Margaritifer Basin, a confluence plain shared with the Uzboi-Holden-Ladon-Margaritifer Valles meso-outflow system (UHLM) that drains northward from Argyre. Detailed geologic and morphometric mapping of the Samara and Parana-Loire valley systems confirms the timing of incisement and permits evaluation of possible mechanisms for valley evolution [2, 5-8].”

[4] Ibid.

“features in Margaritifer Sinus. Four resurfacing events that deposited materials interpreted to be of mostly volcanic origin on the basis of wrinkle ridges and occasionally lobate morphology followed formation of these basins. The first three resurfacing events were

widespread and ended before evolution of the preserved valleys; the first two occurred during early Noachian heavy bombardment [11] and the second ended at an N5 age of 1400 (number of craters >5 km in diameter

per 1,000,000 km2). By contrast, the third resurfacing event began during the middle Noachian (N5 of 500) and ceased during the late Noachian (N5 of 300) coincident with waning highland volcanism [11]. Formation of Samara and Parana-Loire Valles, the UHLM system, infilling of associated depositional sinks (e.g., Parana Basin at 12.50W, 22.50S), and initial collapse of Margaritifer Chaos all occurred from the late Noachian (N5 of 300) into the early Hesperian (N5 of 150). The last, more localized resurfacing event lasted into the early and middle Hesperian (N5 ages 200 to 70) and emplaced materials that embay valleys. Nearly all area surfaces have been subsequently modified to varying

degree by eolian activity.”

[5] Ibid.

“Model for Valley Evolution: A model for valley formation consistent with these results involves mostly localized ground-water discharge enabled by surface fed recharge. In this model, precipitation (rain or snow) would be largely relegated to subsurface entry by high

surface-infiltration capacities. Discharge at exposed relief would be controlled by occurrence of layers/ aquitards. Valley evolution would have continued until draw-down of the water table following cessation

of precipitation, thereby resulting in a strong sapping overprint.

Martian valley formation by this process may best explain observed morphometry. For example, the basin wide distribution of valleys (Fig. 1), low drainage density and ruggedness numbers, degree of integration,

and sediment volume in along-valley sinks may be difficult to accommodate in a hypothesis involving ground-water discharge in the absence of surface recharge. With surface-fed recharge, valley distribution would be controlled mostly by the occurrence of layers/

aquitards.”

[6] D. Williams (2003) “Parana Valles drainage system in Margaritifer Sinus, Mars”  NASA Goddard Space Flight Center.  Image at:

http://nssdc.gsfc.nasa.gov/imgcat/html/object_page/vo1_084a47.html

[7] John A. Grant (2001) “DRAINAGE EVOLUTION IN MARGARITIFER SINUS, MARS” Paper No. 132-0 GSA Annual Meeting, Boston, Massachusetts

Geologic mapping in Margaritifer Sinus, Mars, defines a complex history of water transport, storage, and release that began in the late Noachian and persisted into at least the mid-Hesperian. Collection, transport, and discharge of the water from widely dispersed surfaces were accomplished by systems of differing character flanking opposite sides of the Chryse Trough. Drainage on the western side of the trough was accommodated by the segmented Uzboi-Ladon-Margaritifer mesoscale outflow system that heads in Argyre basin, drains approximately 9% of the Martian surface, and alternately incises and fills as it crosses ancient multi-ringed impact basins.”

[8]March 9, 2000. Goddard Space Flight Centre “View inside Mars reveals rapid cooling and buried channels” Top Story. Available online at  http://www.gsfc.nasa.gov/topstory/20000309mars.html

The crustal structure accounts for the elevation of the Martian northern lowlands, which controlled the northward flow of water early in Martian history, producing a network of valleys and outflow channels. The new gravity-field data suggest that the transport of water continued far into the northern plains. The gravity shows features interpreted as channels buried beneath the northern lowlands emanating from Valles Marineris and the Chryse and Kasei Valles outflow regions.”

[9] K. Lewis and O. Aharonson (2004) “Characterization of the distributory fan in Holden NE Crater using stereo analysis” LPSC XXXV 2083.pdf.

Introduction: The recent discovery of a distributary fan in a large crater northeast of Holden by Malin

and Edgett has been presented as evidence for persistent flow of water on Mars [1]. With at least three

separate depositional lobes and a clearly layered structure, this feature is so far unique among sedimentary

structures on Mars. This fan has been deposited by fluvial processes, and then subsequently eroded back

from its original extent. This process has left behind an inverted topography, with the floors of former channels standing above the surrounding terrain. Several of the remnant channels in this formation appear to display meandering curves, which is the strongest evidence for a steady supply of water at this location.

Further, persistent flow raises the possibility that this feature was, at one time, a lacustrine delta.”

 

[10]M Pondrelli et al (2004) “Complex evolution of Paleolacustrine systems on Mars: an example from the Holden Crater” LPSC XXXV 1249.pdf

Introduction: Lacustrine systems are extremely sensitive to environmental fluctuations and, thus, they represent an ideal geological setting to investigate for climatic changes. Among the putative Martian paleolakes, the Holden crater (26S/326E) (Fig. 1) shows a richness of fluvio-lacustrine features. The Holden crater is 130 km wide and lies on Noachian rocks of the southern-cratered terrains [1]. The crater appears to interrupt a fluvial system of Hesperian age [1] which likely connected the Argyre basin to the northern chaos-outflow channels system. The main valley, Uzboi Vallis, cuts the southern rim and debouches into the crater. The Uzboi Vallis and Holden crater floors have been previously mapped as same units of fluviolacustrine deposits origin reworked by wind activity [2]. These deposits show a variety of sedimentary and morphological differences at MOC and THEMIS scale.”

[11] R.M.E. Williams et al (2004) “Young fans in an equatorial crater in Xanthe Terra, Mars” LPSC XXXV 1415.pdf.

Introduction: In recent years, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC)

investigation has largely focused on NASA’s Mars Exploration Program “Follow the Water” theme. We report here on MOC narrow angle (NA) images obtained in 2003 following observations from 1999 that show a specific, un-named, ~60 km-diameter impact crater at an equatorial latitude (7.6oN, 33.0oW) that exhibits well-preserved landforms similar in planimetric form and morphology to alluvial fans of arid environments such as the Mojave Desert of southern California. The principal question is whether these fans represent the products of water and gravity-driven alluvial sedimentation. The landforms in the Xanthe Terra crater are unique

among MOC images of martian impact craters, with the exception of some features in middle latitude Hale Crater and its central peak (35.9°S, 36.6°W). The purpose of this paper is to present an initial, brief description of these landforms and explore their implications.

Some of the channels display branching networks proximal to the fan (Fig. 3). The channel networks display a third-order topology using Horton’s ordering scheme. First-order tributaries of the channels that feed the fans extend to the crest of local topographic highs. Locally, the density of channels (total channel length per area of network) is extremely high (preliminary value >500 km-1), comparable to terrestrial values for much larger scale rivers in humid environments with highly erodable substrates. In areas of high channel density, channels are visible to the resolution limit of the MOC NA images.”

 

[12] B. M. Hynek and R. J. Phillips (2001) “Evidence for extensive denudation of the Martian highlands” Geology, 29, 407-410.

Using high-resolution topographic data from the Mars Orbiter laser

altimeter (MOLA) instrument on the Mars Global Surveyor mission

(Smith et al., 1999), we have gathered evidence for a major fluvial

resurfacing event in the Martian highlands. We completed detailed geomorphic mapping for the Margaritifer Sinus region (08–308S, 08–

308W), where resurfacing appears most evident. In addition, evidence

from adjacent areas suggests that this was not a localized event, but

one that affected at least 1 3 107 km2 (an area equivalent to the European continent) of the cratered uplands. The topographic information

allows for the first time a separation of younger, low-standing fluvially reworked terrains from older, high-standing erosional remnants. The newly acquired MOLA data also allow the volume of eroded material to be sensibly determined and minimum erosion rates to be estimated. The erosional episode was limited in time to no more than several hundred million years, and occurred ca. 4 Ga. The scale of the processes involved strongly suggests, but does not demonstrate uniquely,

that precipitation must have played a major role in landscape denudation

in this region of Mars.”

[13] Ibid.

 [13] “Formation processes of valley networks are still controversial; the

debate is largely focused on the relative roles of surface runoff and

groundwater processes. In the mapped region, the morphology of the

valleys and associated networks (v-shaped profile, sinuous, high density, and high valley order) and the observation that numerous valleys originate near the tops of crater rims or hilltops (Fig. 3) indicate that precipitation and surface runoff may have played a major role in their formation. Some valleys show morphologies more consistent with a groundwater-sapping origin (u-shaped profile, low density and order, and alcove-like terminations), suggesting that subsurface water was also important. Therefore, both precipitation and groundwater certainly contributed to degradation in the Margaritifer Sinus region, but the relative importance of each erosion mechanism is unclear. These results are consistent with previous work completed on the south-central part of our study area (Grant, 2000).”

http://ltpwww.gsfc.nasa.gov/tharsis/hynek.erosion.pdf

[14] Ibid.

[14] “There is evidence for a large paleolake in the region (Parana basin;

22.58S, 12.58W, area ;33 000 km2) (Goldspiel and Squyres, 1991). The

depression contains hummocky interior deposits with interspersed smooth terrain (Ni) that were emplaced contemporaneously with the extensive denudation and valley network formation. A large number of valley systems terminating at the proposed shoreline of Parana basin are believed to have been sources for the paleolake (Goldspiel and

Squyres, 1991). The unit HNl contains a hematite spectral signature

and is interpreted to be sedimentary layers deposited from large-scale

water interactions (Christensen et al., 2000).”

[15]B. Moomaw  (2001) “Mars: A World of Varied Catastrophes” MARSDAILY May 1, 2001 available online at http://www.spacedaily.com/news/lunarplanet-2001-01a2.html

“J.A. Grant examined the valley networks in the Margaritifer Sinus region, the area on Mars where they are most concentrated, and concluded that they were indeed carved by "sapping" (tunneling by underground water flows) rather than surface runoff -- but also that the only way such a subsurface water supply could be adequately replenished was if "widespread precipitation" in the form of rain or snow occurred in the region and then seeped into Mars' porous ground.

B.M Hynek concluded from MGS' laser topography maps that the western Arabia Terra ("Arabia Highlands"), an area the size of Europe, was so eroded by surface rain that 3 million cubic km of its material was gradually washed into Mars' low-altitude northern plains.

K.P. Harrison and R.E. Grimm examined the fact that the areas on Mars where valley networks seem to be most concentrated are also those where MGS' magnetic sensors -- to everyone's surprise -- found local magnetic fields which seem to be areas where crustal iron minerals have been permanently magnetized by Mars' long-vanished early magnetic field.

Since this most easily occurs when molten rock is exposed to a magnetic field at the same time that it is rapidly cooled into solid form, the obvious possibility is that rising flows of underground magma may have collided in these areas with large amounts of groundwater kilometers below the surface, providing a flow of geothermal hot springs for the valley networks, and also cooling the magma quickly enough to "freeze" a copy of Mars' magnetic field into the resulting solid rock before Mars' magnetic field could reverse polarity (which, like Earth's, it probably did every million years or less) and thus scramble the permanently recorded "fossil" field.

D.M. Nelson examined the highlands south of the Elysium Basin -- through which three especially big channels seem to have carried fluid for a long period -- and concluded that the area showed signs of having undergone repeated cycles of geological peace that would have allowed a local layer of ground ice to build up, and episodes of moderate volcanism just right to melt the accumulated ice and produce large water flows into Elysium.”  Bruce Moomaw “Mars: A World of Varied Catastrophes”

[16]R. J. Phillips et al (2001) “Ancient Geodynamics and Global-Scale Hydrology on Mars”  SCIENCE VOL 291 30 MARCH 2001

“Valley networks were examined in detail (25) in Margaritifer Sinus, a region on the flank of the Arabia bulge and in the Tharsis trough (Fig. 3B). Most formed on regions of relatively high topographic gradient on the flanks of the trough. The majority (;85%) of

observed valley networks here likely formed in Late Noachian time, between ;4.3 to 3.85 billion years ago (Ga) and ;3.8 to 3.50 Ga (26), although the possibility exists that earlier valley networks in this region were destroyed by a high impact flux or alternative erosion mechanisms. Because many of these valley network orientations are controlled by Tharsis-induced slopes, the Tharsis load must be largely Noachian in age, which is consistent with inferences made earlier. Superposition and sequence relationships indicate that

the valley networks whose azimuths are not explained by the model are nevertheless contemporaneous with the Tharsis-controlled valley networks (27). The formation of valley networks in Margaritifer Sinus is intimately associated with a Late Noachian, large-scale erosion event on the flanks of the Tharsis trough that stripped at least 1.5 3 106 km3 of material from this area, leaving behind numerous mesas of Early and Middle Noachian terrain (25).”

 

[17] H. Frey (2001) Geodynamics “2001 The Year in Review” Annual Report of the Geodynamics Branch, Goddard Space Flight Center.

Figure 1 shows two recent magnetic maps of Mars derived using these techniques. The anomalies have a pattern strongly suggestive of faulting and perhaps offset along faults along a major tectonic structure.  The Vallis Marineris on Mars is a series of large, fault-bounded canyons which have been compared with major rift structures on the Earth. The pattern in the magnetic maps, especially the abrupt truncation of the anomalies at the wall of the canyon, supports the idea that the Valles Marineris canyon is a tectonic graben. The maps also suggest that highly magnetic source rocks exist at the intersection of Coprates and Capri Chasmata, on the northeast corner of the canyons, and there is a good possibility that these magnetic rocks may be exposed along the fault wall.”  

[18] M.E. Purucker et al (2001) LPSC XXXII 1865.pdf “Interpretation of a magnetic map of the Valles Marineris region, Mars”.  available online at http://denali.gsfc.nasa.gov/terr_mag/abstract_mars.pdf

 

[19] B. Murray [1999] “PALEOLAKE DEPOSITS IN CENTRAL VALLES MARINERIS: A UNIQUE OPPORTUNITY FOR 2001” Second Mars Surveyor landing site Workshop.

“Paleolake deposits have been mapped in Central Valles Marineris since Mariner 9 and Viking

(McCauley, 1978; Nedell et al., 1988;Witbeck et al., 1991). Accordingly, the region has been proposed as a priority target for landed payloads intended to detect diagnostic mineral evidence of a permanent lake environment, and, especially, biogenic signatures that could have survived from such promising candidate Martian habitats. (eg, Murray, et al, 1996; Yen, et al, 1999, Murray, et al, 1999). Just-released MOLA data strongly buttress the hydrological case for longduration ice-covered lakes there during Hesperian times at least.”

[20] Ibid

“Carr (1996) suggested that ground water flowed from the Tharsis uplands into the deep canyons of Valles Marineris before debouching onto Chryse Planitia in the northern plains. Such a flow may have persisted for billions of years, and is generally inferred to have maintained deep lakes beneath which lacustrine sediments accumulated. Remnants of these Hesperian Age lake deposits survive today as conspicuous layered strata in Central Valles Marineris. Just published MOLA data (Smith, et al, 1999) confirm in detail this topographic trend and, most importantly, prove that deep, permanent lakes did indeed exist, especially in Central and Western Valles Marineris. Because the canyons in the Valles Marineris are deeper than the probable ground water table at that period, large portions of the canyons would have filled with water and formed ice-covered lakes.”

[21] A.P. Rossi et al (1999)  “[46.03] Flow-like features in Valles Marineris, Mars: Possible ice-driven creep processes” 31st Annual Meeting of the DPS, October 1999 Session 46. Mars Surface: Evidence of Change Posters .

Recent high resolution MOC images have revealed the presence of deformed impact craters on flow-like features characterized by narrow bands of alternating light and dark material on the walls of Valles Marineris. The maximum crater elongations are consistent with the flow directions. Moreover the directions of these flows follow the topography downslope. In some cases, the flows emanate from cirque-like depressions, and the flows are divided by sharp ridges similar to arête. These landforms have resemblance to (1) alpine-type glacier morphology, including cirques, arêtes, and glaciers containing medial moraines; and (2) Grand Canyon-type sapping and mass wasting features. Certain aspects of the features in Valles Marineris seem more consistent with the first hypothesis involving a viscous rheology of the flows driven by ice-assisted creep processes. This hypothesis includes direct analogies to glaciers and rock glaciers. In the case of rock glaciers, flow is produced by freeze-thaw and by internal deformation of ice cores or lenses, whereas in the case of glaciers, movement occurs by internal deformation plus basal sliding in some cases where the glacier is melted at its bed. The amounts and roles of ice in the genesis of the Martian glacier-type landforms in Valles Marineris are not clear at this point. The population density of undeformed fresh impact craters on these flows appears to be low compared with the surrounding plateau areas. This may indicate relatively recent ages of the flow processes.”

[22]  R. Greeley and R. Kuzmin (1999) “SHALBATANA VALLIS: A POTENTIAL SITE FOR ANCIENT GROUND WATER” 2nd Mars Surveyor landing site workshop, SUNY/Buffalo, 43-44

available online at http://www.aas.org/publications/baas/v31n4/dps99/158.htm

The channel is unusual because it appears to represent a single outflow initiated by a large impact. This impact could have excavated materials from the Martian crust from depths of several kilometers, apparently “tapping” the aquifer system leading to catastrophic

flooding to form the channel. Ejecta from the Noachian impact crater [6, 7] is preserved NW-W and SE from the source area. The width of Shalbatana Vallis near its source is about 50 km and then it continues 500 km NE as a sinuous, narrow channel of nearly constant width (10 -20 km cross) and depth (~2 km). The channel then becomes wider (40-50 km), bifurcates, and enters Simud Vallis [7].”

 

[23] D.M. Nelson and R. Greeley (1998) “XANTHE TERRA OUTFLOW CHANNEL GEOLOGY AT THE MARS PATHFINDER LANDING SITE” LPSC XXIX 1158.pdf.

Summary. Geologic mapping of southern Chryse Planitia and the Xanthe Terra outflow channels has revealed a sequence of fluvial events which contributed sediment to the Mars Pathfinder landing site (MPLS). Three major outflow episodes are recognized: (1) broad sheetwash across Xanthe Terra during the Early Hesperian period, (2) Early to Late Hesperian channel formation of Shalbatana, Ravi, Simud, Tiu, and Ares Valles, and (3) subsequent flooding which deepened the channels to their current morphologies throughout the Late Hesperian. Materials from the most recent flooding, from Simud and Tiu Valles, and (to a lesser extent) materials from Ares Vallis, contributed the greatest amount of sediment to MPLS.”

[24] Ibid.

Following sheetwash, Mawrth Vallis was formed, possibly resulting from the discharge of floods from Margaritifer and Iani Chaos. A broad area of subdued terrain east of Ares Vallis indicates buried and embayed craters to the south of Mawrth Vallis. Floods could have passed over this surface before excavating Mawrth, then drained downslope into Acidalia Planitia. Alternatively, the subdued area could be a spill zone formed during the early excavation of Ares Vallis. Channelization continued in the Late Hesperian with the development of Shalbatana, Ravi, Simud, Tiu, and Ares Valles. Shalbatana Vallis possibly formed by subterranean discharge from Ganges Chasmata [7], and Ravi was excavated by flooding from Aromatum Chaos. Simud and Tiu Valles then developed by floods from Hydraotes and Hydaspis Chaos, and Ares Vallis developed by flooding from Iani Chaos. Cross-cutting relationships in Ares and Tiu Valles suggest that multiple floods occurred within these channels.”  

[25] P. D. Lanagan et al (2001) “GEOMORPHOLOGIC MAPPING OF CERBERUS PLAINS, MARS” LPSC XXXII 2077.pdf

Fluvial features in the Cerberus plains cut into and are covered by lava flows [2]. MOC images, which show streamlined islands and longitudinal grooves, and MOLA topography suggest that water that carved the more recent of these channels originated from Cerberus Rupes or in regions of ground collapse highland rem-nants north of Cerberus Rupes, ran south into the Cer-berus plains, and finally emptied into Amazonis Plani-tia via the Marte Valles outflow channels [1].”

[26] Lanagan et al (2001) Rootless cones on Mars indicating the presence of shallow equatorial ground ice in recent times”, Geophysical Research Letters, vol. 28, p. 2365-2368.

Clusters of small cones on the lava plains of Mars have caught the attention of planetary geologists for years for a simple and compelling reason: ground ice. These cones look like volcanic rootless cones found on Earth where hot lava flows over wet surfaces such as marshes, shallow lakes or shallow aquifers. Steam explosions fragment the lava into small pieces that fall into cone-shaped debris piles. Peter Lanagan, Alfred McEwen, Laszlo Keszthelyi (University of Arizona), and Thorvaldur Thordarson (University of Hawai`i) recently identified groups of cones in the equatorial region of Mars using new high-resolution Mars Orbiter Camera (MOC) images. They report that the Martian cones have the same appearance, size, and geologic setting as rootless cones found in Iceland. If the Martian and terrestrial cones formed in the same way, then the Martian cones mark places where ground ice or groundwater existed at the time the lavas surged across the surface, estimated to be less than 10 million years ago, and where ground ice may still be today.”

 

[27] (2003) Los Angeles National laboratory News and Public Affairs, News Releases, Photos. Available online at:  http://www.lanl.gov/orgs/pa/News/cover_epi.jpg

[28] M. Caplinger  February (1994) “Determining the age of surfaces on Mars” Malin Space Science Systems, Available online at:

http://www.msss.com/http/ps/age2.html

[29] D. E. Smith and M. T. Zuber (2004) “Gravitational effects of flooding and filling of impact basins on Mars” LPSC XXXV 1923.pdf.

Introduction. The presence of large impact basins and the low northern plains that might have contained ice or liquid water at an earlier stage of Mars’ evolution suggests that the global gravity field could have been different in the distant past than it is today. In addition, any significant change in the distribution of mass affects the moments of inertia and consequently and could conceivably change the position of the Polar Cap and the length of day. Similar effects could have been produced by large erosional processes, such as the removal of crustal material from the Arabia Terra region and subsequent re-depostion in the Chryse region of the northern plains [1]. We have endeavored to estimate the magnitudes of material that might have been involved in these processes and their possible effect on the gravity and dynamics of Mars. We have used present-day topography [2] and gravity field [3] as a starting point, recognizing that both the result of the processes that we are trying to study rather than the state at the times of interest.

Basin Volumes. The largest volume (arbitrarily defined below zero elevation) that could have been filled with H2O in the past is the northern plains (Fig. 1a) , which occupy about 47% of the surface of the planet [2]. Because of its location, which is approximately symmetrical about the Polar Cap, the additional mass associated with flooding contributes largely to the zonal gravity field, particularly degrees 1, 2 and 3, with small changes to the moments of inertia. (Note: we do not account for flexural effects.) Hellas (Fig. 1b) is the largest impact basin, and if filled to the zero

elevation level would only hold about 10% of the volume of the northern plains. But because of its location at 30 to 50S, 50 to 90oE, it has the potential to have a larger effect on the moments. If suddenly filled today it would want to move toward the equator and because it is almost antipodal position to Tharsis it would move Tharsis southward [cf. 4]. The second largest impact basin was probably Utopia [5, 6] but today it is filled with sediments and volcanics [7], thus making the basin much shallower than it was originally. It appears to have been a Hellas sized basin and therefore might have been a significant contributor to global-scale mass re-distribution. Argyre, in comparison to Hellas, has only about 10% of the volume of Hellas as measured by today’s topography, and has a relatively minor effect on the global mass redistribution.”

[30] A. T. Oner et al (2004) “The volume of possible ancient ocean basins in the Northern Lowlands  LPSC XXXV 1319.pdf.

Discussion: Our results for Arabia and Deu-teronilus shoreline present-day topography are some- what lower than those obtained previously [7,8]. the Meridiani shoreline our result is clearly lower than

that in [8], fundamentally due to the fact that these authors use an excessively high value of 0 (with re-

spect to the global datum) for the mean paleoshoreline elevation, whereas we use a mean elevation of −1.5 km [17]. Elevational range and geologic relations along Ara-bia shoreline, especially with respect to the Tharsis region, suggests that this is not a true paleoshoreline [7,8]. This implies that volumes obtained for the Ara-bia shoreline are likely not representative of any an-cient martian ocean. Otherwise, elevations in the puta-tive Meridiani shoreline are roughly similar to those of  the Arabia shoreline in northeast Arabia, Utopia (not taken into account the Isidis basin), Elysium, and Amazonis regions. A paleoshoreline through these Arabia shoreline portions and the Meridiani shoreline would be a better candidate to represent a true ancient oceanic limit [5,18]: areas, volumes, mean depths and GELs obtained here for the Meridiani shoreline would be roughly valid for this possible paleoshoreline.”

 

[31] (2003) Los Angeles National laboratory News and Public Affairs, News Releases, Photos. Available online at:  http://www.lanl.gov/orgs/pa/News/cover_epi.jpg

Also JPL 2002 image releases, Global Map of Epithermal Neutrons, May 28 2002, PIA 3800. Available online at: http://www.jpl.nasa.gov/images/mars/pia3800_caption.html

[32] Greg M. Orme and Peter K. Ness (2003) “Martian Spiders” New Frontiers in Science, Fall 2003. Viking Spiders. Available online at:  http://newfrontiersinscience.com/Members/v02n03/a/NFS0203a.shtml

“Oddly enough, Viking 2 [137] landed [138] nearly in the middle of a sub polar area that seems truly spider like [139]. Interestingly, some troughs were found near Viking 2 [140]. While other explanations have been suggested, the presence of the spiders nearby and their association with sometimes polygonal ravines makes these troughs possibly spider ravines. These "enigmatic troughs" [141] can be traced in a sequence of photos [142]. If they are spider ravines, it might indicate that when the spiders seasonally dissipate, they might leave ravines that are too shallow to see. There are also pits [143] in the area of unknown origin. In The Martian Landscape , Figures 195 [144],199[145], and 200 [146] may also be troughs. Figures 290, 210 and 211 [147] show paler areas devoid of rocks, which may be related to spiders. Of course, there are many other explanations but the proximity to the spiders makes these interesting. In imagery of the landing site [148], spider branches are 1-3 pixels wide where a pixel's width [149] is 9.46 meters [150]. Since spiders typically have a paler albedo and a comparable branch width to these pale patches, it is possible that they might be spider remnants.”

 

[33]Peter K. Ness and Greg M. Orme, (2002).Spider-Ravine Models and Plant-like Features on Mars - Possible Geophysical and Biogeophysical Modes of Origin” Journal of the British Interplanetary Society, 8 February 2002. Vol 55 No 3/4, March-April Edition, Pp 85-108. available online at http://www.martianspiders.com

 

[34] D. E. Shean and J. W. Head (2003) “Pavonis Mons fan-shaped deposit- a cold based glacial model” 6th International Conference on Mars 3036.pdf

Introduction: Each of the three Tharsis Montes volcanoes on Mars has unusual fan-shaped deposits

located exclusively to the west-northwest of each shield. The fan-shaped deposits of the Tharsis Montes

generally share three major facies: 1) a ridged facies, 2) a knobby facies, and 3) a smooth facies. Any ex-

planation for the origin of the fan-shaped deposits must take into account both the similarities and differences in their morphologies, their approximately similar Amazonian age, and the fact that all three occur on the west-northwestern sides of the volcanoes [1]. Based on Viking Orbiter data, several models have been pro- posed for their formation, including massive landslides [2], glacial processes [3,4,5,6] and pyroclastic flows [6]. We support a glacial origin for the fan-shaped deposits and refine the previous models using new data from both the Earth and Mars. Based on Viking Or-biter data, Williams [3] and Lucchitta [4] suggested that the fan-shaped deposits were the result of the deposition of moraines due to recession of local ice caps that formed on the volcanoes from mixtures of emanated volatiles and erupted ash [4]. Scott et al. [6] suggest an explanation combining glacial and volcanic processes

We interpret these ridges as drop moraines formed at the margins of a retreating cold-based glacier [7].

The fact that these ridges can be seen in the proximal regions of the Pavonis fan-shaped deposit suggests that at least one major phase of retreat and deposition oc-curred. The ridges are superposed on underlying to-pography, including a lobate lava flow to the west, and are not deflected by obstacles. The fact that the ridged facies is observed up to elevations of 9.2 km above Mars datum on the northern flanks of Pavonis suggests that a large glacier would have covered a significant portion of the flanks of the shield.”

 

 

[35] E.R. Fuller and J.W. Head III (2002) “GEOLOGIC HISTORY OF THE SMOOTHEST PLAINS ON MARS (AMAZONIS PLANITIA) AND ASTROBIOLOGICAL IMPLICATIONS” LPSCXXXIII 1539.pdf

The cryosphere, a frozen layer of ice and regolith, has been acting as a global aquitard to the groundwater system below [e.g., 9]. Once the cryosphere is breached, the water, under hydrostatic pressure, emerges with very high flow rates, and continues flowing until pressure equilibrium is reached. This water flowed through Marte Vallis, eroding channels and debouching into Amazonis Planitia. This catastrophic outflow was shortly followed by lava outflow; the magma flowed through the fracture and released flood lavas onto the surface. This lava followed the path of the water, re-surfacing Marte Vallis and pouring into Amazonis

Planitia. As it flowed over the water-saturated surface, the phreatomagmatic interactions created rootless cone structures [see also discussion in 10]. Astrobiological implications: The lava flows associated with the emplacement of these plains have been dated as extremely young geologically (less than 10 million years old [11]). If fossil or extant life existed at depth in the subsurface groundwater system at this time (a troglodytic fauna), it is highly likely that they would be among the material erupted to the surface, and washed down into Elysium Planitia and Amazonis Planitia. The fate of such effluents under current martian conditions has recently been modeled [12] and it has been shown that standing bodies of water at this scale would quickly freeze over and sublimate, leaving a sedimentary sublimation residue. Thus, Elysium and Amazonis Planitiae would be excellent locations to sample recently emplaced freeze- dried troglodytic faunal remains.”

 

[36] JPL Planetary Photojournal PIA04253 “Map of Martian Iron at mid-latitudes”. Available online at:

http://photojournal.jpl.nasa.gov/catalog/PIA04253

[37] O. Aharonson et al (1998)  “Mars: Northern hemisphere slopes and slope distributions” GEOPHYSICAL RESEARCH LETTERS, VOL. 25, NO. 24, PAGES 4413-4416, DECEMBER 15, 1998.

Characterization of Martian surface slopes from the aerobreaking hiatus phase of the MGS mission provided several insights. Regional slopes across prominent canyons measured on a 10-km baseline range from 0 5_ for regions which have undergone mass wasting and collapse, up to approximately 30_ for less modi_ed scarps. The average slopes across the dichotomy boundary are small, < 1_, but on a local

scale can execed 20_. The northern lowlands are found to be unusually smooth and form a distinct statistical population. Other distinct populations correspond to the rough highlands and the extremely smooth Amazonis Planitia region. Amazonis is markedly smoother than any other large scale surface observed onMars, than volcanic plains on both the Moon and Venus, and than an example of desert terrain on the Earth. Its statistical properties resemble most closely certain terrestrial depositional environments including

oceanic abyssal plains and sedimentary basins. Given previously hypothesized scenarios for Mars' geological past [Carr, 1981], the evidence so far may be consistent with an origin for Amazonis in which extensive aeolian deposition follows a volcanic resurfacing event. Also possible is a modicational history in which water provides a sedimentary environment capable of efficiently smoothing meter scale topography.”

 

[38] E. R. Fuller and J. W. Head III (2002) “Amazonis Planitia: The role of geologically recent volcanism and sedimentation in the formation of the smoothest plains on Mars” JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. E10, 5081, doi:10.1029/2002JE001842, 2002.

[9] Parker et al. [1993] drew Contact 2, one of two interpreted shorelines for their proposed Hesperian northern ocean, near the margins of the central smooth unit of Amazonis Planitia. Head et al. [1999], using MOLA data, assessed the elevation of the two contacts, and found that Contact 1 deviated substantially from an equipotential line, but that Contact 2 was much closer to being level, with a mean elevation of 3760 m below the Martian datum. Figure 5e shows the trace of the _3760 m contour through the

Amazonis Planitia region.

[10] Morris and Tanaka [1994] mapped the eastern edge of Amazonis Planitia in their analysis of the Olympus Mons region. They identified two plains subunits of the Arcadia Formation (Figure 2): Aa1 and Aa2, both volcanic plains mantled by aeolian deposits. They also present evidence that the age of mapped volcanic units associated with Olympus Mons span the Middle to Late Amazonian, and that if the

aureole deposits represent the collapse of a proto-Olympus Mons edifice, then extrusive activity must have extended back to the Late Hesperian. On the basis of their mapping, they favor a landsliding and gravity-spreading mechanism [see also Tanaka, 1985; Francis and Wadge, 1983], but point out that this requires a lubricant such as water or ice. They further point out a weakness of their hypothesis: ‘‘if a huge,

proto-Olympus Mons had formed (necessary for the landsliding and gravity-spreading mechanisms), extant lava flow fields beyond the aureoles might be expected, but they are absent’’ [Morris and Tanaka, 1994, p. 15].

Its smoothness is comparable only with Earth regions shaped by long-term aqueous deposition, such as ocean floors and the North American Great Plains (the former location of an epeiric sea) [Aharonson et al., 1998]. Re-examination of Pass 31 shows that the smoothest region within the several thousand

kilometer-long track corresponds precisely with the central smooth unit of Amazonis Planitia identified in this study (Figure 7).”

[40] M. A. de Pablo (2004) LPSC XXXV 1223.pdf.

The subsequent evolution of Atlantis Basin is closely related to the evolution of Eridania Lake. The

desiccation of Eridania Lake, probably during the Late Noachian [5], might have predated the existence of a series of reduced and interconnected lakes in the area, in which Atlantis might have been included. In this

work we propose the name Atlantis Lake for the lake formed inside this basin and originated in the decrease

of the water level of the Eridania Lake. Water probably flowed in the area from the South, initially

draining to Southwest, but later forming an endorreic basin until its complete desiccation. In relation with

this evolutionary sequence, the presence of ‘mesas’ in the basin edges (Fig. 1-f) have been interpreted as

sedimentary materials deposited in the floor of the ancient Eridania Lake, and subsequently eroded. This

interpretation, together with the presence of relatively recent collapse areas (Fig. 1-g) and mud-flow deposits (Fig. 1-h) around the Atlantis Chaos terrain, indicate the existence of liquid water in the recent past. The appearance of linear structures in the interior of Atlantis basin has been interpreted as indicative of possible ancient dike systems [8], whose new activation would explain the existence of the

subsidence zones and the mud-flow deposits by the fusion of the permafrost. Equally, the presence of

gullies (Fig. 1-i) in several closed basins near to Atlantis Basin (as Gorgonum Chaos [9]), makes

feasible the existence of recent liquid water under the surface [10] [11] [12] [13].

Astrobiological interest: The intense volcanic and tectonic activities, and the presence of possible

dikes in the area, as well as the relation of Atlantis with the former wide Eridania Lake, the gullies, and

the sedimentary deposits, all highlight the astrobiological interest of Atlantis. A heat source

related to tectonovolcanic activity and flowing and ponded water are both hypothesized to have been

present in the basin in different periods of the Martian history, perhaps until recent times (Late Amazonian).”

 

[41] Mars Exploration Rover Mission Press Releases (April 1, 2004). Available online at:

 http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20040401a.html

Gusev is halfway around the planet from the Meridiani region where Spirit's twin, Opportunity, recently found evidence that water used to flow across the surface.

"This is not water that sloshed around on the surface like what appears to have happened at Meridiani. We're talking about small amounts of water, perhaps underground," said Dr. Hap McSween, a rover science team member from the University of Tennessee, Knoxville.

"The evidence is in the form of multiple coatings on the rock, as well as fractures that are filled with alteration material and perhaps little patches of alteration material," McSween said during a press conference at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

 

[42]Mars Exploration Rover Mission Press Releases (March 5, 2004). Available online at:

 http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20040305a.html

NASA's Spirit has found hints of a water history in a rock at Mars' Gusev Crater, but it is a very different type of rock than those in which NASA's Opportunity found clues to a wet past on the opposite side of the planet.

A dark volcanic rock dubbed "Humphrey," about 60 centimeters (2 feet) tall, shows bright material in interior crevices and cracks that looks like minerals crystallized out of water, Dr. Ray Arvidson of Washington University, St. Louis, reported at a NASA news briefing today at NASA's Jet Propulsion Laboratory, Pasadena, Calif. He is the deputy principal investigator for the rovers' science instruments.

"If we found this rock on Earth, we would say it is a volcanic rock that had a little fluid moving through it," Arvidson said. If this interpretation is correct, the fluid -- water with minerals dissolved in it -- may have been carried in the original magma that formed the rock or may have interacted with the rock later, he said.”

 

[43] R. P. Irwin III and T. A. Maxwell (2004) LPSC XXXV 1852.pdf.

Introduction: At 900 km long, 8−15 km wide and up to 2,100 m deep, Ma’adim Vallis is one of the largest valleys in the Martian highlands. The valley descends northward and terminates at the landing site for the Spirit Mars Exploration Rover at Gusev Crater, which acted as a detention pond or terminal basin for Ma’adim flows [1]. Previously we identified the valley head at the breached drainage divide of an enclosed basin in the mid-latitude highlands. Along with characteristics of the head basin, this feature suggested that the valley was carved primarily during a single paleolake overflow at the Noachian/Hesperian boundary [2] (~3.7 Ga [3]). Earlier work had suggested that Ma’adim Vallis was carved over a prolonged period up to 1.8 Ga by episodic groundwater-fed flows [4−10]. Here we investigate the valley’s longevity using crater counting, topography, and flow hydraulics. These

analyses provide quantitative support for development of the valley during a brief overflow, followed by a

geologically brief period of tributary development.”

 

[44] K. L. Thomas-Keptra et al (2004) “Determination if the three-dimensional morphology of ALH84001 and biogenic MV-1 magnetite: comparison of results from electron tomography and classical transmission electron microscopy” LPSC XXXV 2030.pdf. 

Introduction Dated at ~3.9 billion years of age, carbonate disks [1], found within fractures of the host rock of Martian meteorite ALH84001, have been interpreted as secondary minerals that formed at low temperature [e.g., 2] in an aqueous medium [e.g., 3]. Heterogeneously distributed within these disks are magnetite nanocrystals that are of Martian origin. Approximately one quarter of these magnetites have morphological and chemical similarities to magnetite particles produced by magnetotactic bacteria strain MV-1 [4], which are ubiquitous in aquatic habitats on Earth. Moreover, these types of magnetite particles are not known or expected to be produced by abiotic means either through geological processes or synthetically in the laboratory. The remaining three-quarters of the ALH84001 magnetites are likely products of multiple processes including, but not limited to, precipitation from a hydrothermal fluid, thermal decomposition of the carbonate matrix in which they are embedded, and extracellular formation by dissimilatory Fe-reducing bacteria. We have proposed that the origins of magnetites in ALH84001 can be best explained as the products of multiple processes, one of which is biological.

 

[45] H. J. Leask et al (2004) “The formation of Aromatum Chaos and the water discharge rate at Ravi Vallis” LPSC XXXV 1544.pdf.

Summary: The Aromatum Chaos depression- Ravi Vallis outflow channel system is sufficiently

simple that water flow rate and volume estimates can be made that throw light on processes operating to

form the Aromatum and Ravi features. Typical discharge rates through Ravi Vallis are estimated at 3

x 106 m3 s-1. By assuming a high sediment load in the water we find a minimum duration of ~2 months.

Too much water flowed in the channel to be explained by cryosphere melting alone, and drainage

of a local aquifer system delineated by intrusions is clearly implicated.

Aromatum Chaos: The main Aromatum Chaos depression is a truncated triangle ~92 km long and an

average of 30 km wide (Fig. 1). Its interior consists mainly of a mass of blocky-chaotic terrain, with

blocks generally becoming progressively smaller towards its Eastern end. Some larger blocks at the

Western end show some evidence of rotational slumping and also appear to be less eroded, having

flat tops showing a rather angular connection between the flat top and the walls. The edges of

Aromatum Chaos show strong evidence of local structural control and so, in an attempt to look for

similar control of the interior, we examined all MOLA profiles crossing the interior, and found 30

profiles which collectively crossed the tops of 20 blocks. From these we measured the absolute heights

(relative to Mars datum) of the tops of the blocks and their depths below the rim of the depression. The

tops of blocks lie between 1,008 m and 2,361 m below the rim and show no systematic correlation

with depth below rim or height above floor, suggesting piecemeal collapse rather than a structural

control on their subsidence.”

 

[46] N. Coleman (2004) LPSC XXXV1299.pdf.

Floodwater Sources: Confined groundwater was the apparent source for the initial outflows. If this were the only source the flow could not have been sustained because confined aquifers, once released, tend to depressurize rapidly. The unconfined dewatering of an aquifer takes much longer. In addition, the presence of an ice-covered lake in ancestral Ganges Chasma would

have provided a substantial reservoir to recharge the aquifer source for both Ravi V. [7] and Shalbatana V. [7, 10], permitting outflows over an extended period. If the flows were concurrent, then the flooding occurred in mid- to upper-Hesperian because Shalbatana V. incised

ridged plains material of lower Hesperian age [11].”

 

[47] C. Woodworth-Lynas and J. Guigne (2004) “Extent of floating ice in an ancient Echus Chasma/Kasei Valles valley system, Mars” LPSC XXXV 1571.pdf.

Introduction: From images of the Echus Chasma/Kasei Valles valley system we present further, new observations of surficial Martian features that are interpreted to be the result of interactions between the keels of flat-bottomed floating ice floes with a submerged sediment [1,2]. These features are proxy indicators of three basic environmental conditions: the former presence of a water body; the water body was seasonally, or perhaps permanently, covered by ice floes; the water area was large enough for winds, currents or both to drive the floes forward during ice/lakebed interaction. We also present an analysis of shorelines. These observations are made from analyses of Mars Global Surveyor Mars Orbiter Camera (MOC) images. In places we have observed several, closely-spaced, terraces

interpreted to be shorelines preserved at different elevations along the margins of the valley system. We use the geographic distribution of the floating ice-related features and shoreline terraces to define the limits of floating ice in the valley system. We compare the shoreline boundaries with equipotential (waterline) surfaces using Mars Orbital Laser Altimeter (MOLA) data, and estimate the volume of water and floating ice that occupied the valley system.”

 

[48] T. Nakamura and E. Tajika (2002) “Evolution of the climate system of Mars: effects of obliquity change” LPSC XXXII 1057.pdf.

The obliquity change could cause a climate jump in the Martian climate system on short timescale. Figure

2 shows the annual mean atmospheric pressure as a function of the obliquity. The present solar constant

and 2.0 bar of the total amount of CO2 in the system are assumed for a nominal example. There are two

branches of the solution. One is a “cold” residual-cap solution branch, and the other is a “warm” no-ice-cap

solution branch. It is noted that the residual-cap solution branch disappears in higher obliquity region. On

the other hand, the no-ice-cap solution branch does not exist in lower obliquity region. Therefore, climate

jumps should occur at the ends of two branches. Assuming the state I in Figure 2 as an initial state, for

example, when the obliquity increases, the state should change to be the state II. If the obliquity continues to increase, a climate jump will occur from the state II to III to reach the state IV. This climate jump results in a drastic increase in the atmospheric CO2 pressure, thus warming. On the other hand, starting from the state is IV, if the obliquity decreases, the state changes from the state IV to I via a climate jump from the state V to VI. In this case, the climate jump results in a decrease in the atmospheric pressure, thus cooling. It is, therefore, suggested that the Martian climate could have dramatically changed repeatedly in short-term cycles during the Martian history.”

 

[49] N. G. Barlow and J. M. Dohm (2004) “Impact craters in Arabia Terra, Mars” LPSC XXXV 1122.pdf.

Discussion: Crater morphologic and central pit data suggest that Arabia hosts a subsurface volatile rich

reservoir of ice and possibly liquid water. The crater data are just one indicator of the uniqueness of

Arabia Terra. The combined stratigraphic, topographic, structural, crater, geomorphic, geophysical,

elemental, and thermophysical signatures suggest that Arabia is unusual compared to other highlands regions [1]. GRS neutron spectrometer data reveal Arabia to be one of the most H2O-rich areas in the equatorial region of Mars [10, 11]. The correlation of this region with crater indicators of subsurface volatiles suggest that volatiles exist over a range of depths in this region, from less than a meter (GRS/NS analysis) to over 2 km depth (based on crater depth-diameter analysis). The existence of ejecta and central pit features over a range of crater preservation ages indicates that this volatile reservoir has existed for a substantial amount of Martian history, perhaps extending back into the Noachian based on the ages of ejecta craters [12].”

 

[50] J. M. Dohm et al (2004) “Ancient giant basin/aquifer system in the Arabia Region, Mars”. LPSC XXXV 1209.pdf.

Magnetic anomalies are observed in this region, although the magnitude is diminished relative to the anomalies in the Terra Cimmeria region [1,2]. The impact would have  erased any preexisting magnetic anomalies in the crust as is seen with Hellas and Argyre. If, however, the impact occurred when the dynamo was active, the crust would have a chance to reacquire magnetization. The diminished intensity could indicate that the dynamo was active but in a waning stage. On the other hand, the reduction in magnetic signals may be the result of deep burial by basin infill. Although there is no geophysical manifestation of a large buried impact basin in the gravity or magnetic data (e.g., circular positive mascons as noted for Argyre, but subdued for Hellas), the extreme age of the event may preclude any detectable geophysical signature and may in fact explain the uniform appearance of the gravity.”

 

[51] J. Arkani-Hamed and D. Boutin (2003) “Polar wander of Mars: Evidence from magnetic anomalies” Sixth International Conference on Mars. 3051.pdf.

Introduction: The polar wander of Mars has been suggested by many investigators. The

quasi-circular surface morphology of the deposits in the polar region detected by Mariner 9 mission led Murray and Malin [1973] to suggest that the Martian rotation axis has wandered by 10-20 degrees in the last ~100 Myr. Melosh [1980] gradually removed the mass of Tharsis bulge

while diagonalizing the moment of inertia tensor of Mars, and showed that the Martian rotation

axis has displaced by about 25 degrees due to the formation of the bulge. The similarity between

the deposits on Mesogaea, south of Olympus, and those in the polar region led Schultz and Lutz

[1988] to suggest a polar path with a total of 120 degree wandering. Long-term rotational dynamics of Mars was theoretically investigated by Spada et al. [1996] through modeling Olympus mountain as a point mass, initially located at 45 degree latitude on the surface, and allowing the mass to reach the equator. They considered a comprehensive suit of internal structure models of Mars with mantle viscosity ranging from 1021 to 1023 and imposed the Murray and Malin's constraint of 10-20 degree polar wander in the last 100 MYr. The authors concluded that the mass will reach the equator within less than 2 Gyr., in a much shorter time for low viscosity mantle models. It is also shown that a thick elastic lithosphere atop a viscous mantle increases polar wander because of elastically supporting the surface mass and allowing its greater influence on the rotational dynamics of Mars [Willmann, 1984; Stiefelhagen, 2002]. The Mars Global Surveyor magnetic data have provided new evidence for the polar wander of Mars. Arkani-Hamed (2001a) estimated the paleomagnetic Polar Cap positions of Mars through modeling 10 small and isolated magnetic anomalies. Seven out of the 10 Polar Caps clustered within a radius of 30 degrees centered at 25N, 225E. Hood and Zakharian (2001) modeled the source bodies of two magnetic anomalies near the north Polar Cap. One of the anomalies was included in the 10 anomalies modeled by Arkani-Hamed, and the Polar Cap positions of this anomaly determined by the authors were very close. Assuming that the diPolar Cap core field axis coincided with the rotation axis, the clustering of the Polar Caps suggests that the rotation axis has wandered by about 65 degrees since the magnetic source bodies were magnetized. This critical assumption that links the diPolar Cap core field axis to the rotation axis presently holds for both terrestrial planets with active core dynamo, Earth and Mercury, and possibly for Earth throughout its history. We make the same assumption in this paper.”

 

[52] I.G. Mitrofanov et al (2004) “Arabia and Memonia equatorial regions with high content of water: data from HEND/ODYSSEY” LPSC XXXV (2004) 1640.pdf.

Results. The consistency of HM and DLM with observational data was tested for the samples of pixels for

Arabia and Memnonia. It was shown that DLM model is better supported by the observational data for Arabia and Memnonia in comparison with HM. The best fitting values of parameters down were used for estimation of water content at these regions. It was shown (see [7]) that North Arabia (0-45E, 0-30S) contains on average 9.0 wt% of water under a dry layer with thickness of 26 g/cm2; the South Arabia (0-45E, 0-20S) contains on average 10.0 wt% of water under a dry layer with thickness of 32 g/cm2; the Memnonia (180-200E, 0-25S) contains on average 9.0 wt% of water under a dry layer with thickness of 29 g/cm2. One particular surface element with coordinates (30E, 10N) has the smallest emission of epithermal neutrons in the equatorial belt (Figure 2).The best fitting subsurface parameters for this element correspond to 16 wt% water under a dry layer with thickness 29 g/cm2 [7]. This estimate for the dry layer is consistent with the average value found for the entire North Arabia. Therefore, this result showing a high content of water at this surface element is not produced by uncertainties in the model-dependent data deconvolution. The value of 16 wt% corresponds to a real minimum in epithermal neutron flux in Arabia. We name this spot “Arabian Water-Rich Spot”, or AWRS. It lies around an old eroded crater between craters Cassini and Schiaparelli.”

 

[53] J.B. Dalton et al (2004) “Search for evaporate minerals in Flaugergues Basin, Mars” LPSC XXXV 1869.pdf.

the Flaugergues drainage divide in the Noachis region of Mars (16.8 S, 340.8 W; [4]) indicates areas

of water accumulation (Fig. 1). Putative paleolakes residing in craters (e.g., Gusev Crater, Schiaparelli)

have already been examined for evidence of aqueous minerals. However, basin flow models suggest that

craters deeper than low-lying basins do not necessarily drain large areas. Raised crater rims often

isolate craters from their surroundings. The model has identified areas of water accumulation fed by

large geographic areas which could produce enhanced transport of aqueous materials. MOLA A shaded-relief map constructed from MOLA data was used to assess the geomorphology of putative paleolake basins. Many were found to exhibit smooth features suggestive of a lake bottom.”

 

[54] Mars Exploration Rover Mission Press Releases (March 2, 2004). Available online at:

http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20040302a.html

Scientists have concluded the part of Mars that NASA's Opportunity rover is exploring was soaking wet in the past.

Evidence the rover found in a rock outcrop led scientists to the conclusion. Clues from the rocks' composition, such as the presence of sulfates, and the rocks' physical appearance, such as niches where crystals grew, helped make the case for a watery history.

"Liquid water once flowed through these rocks. It changed their texture, and it changed their chemistry," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the science instruments on Opportunity and its twin, Spirit. "We've been able to read the tell-tale clues the water left behind, giving us confidence in that conclusion."

Dr. James Garvin, lead scientist for Mars and lunar exploration at NASA Headquarters, Washington, said, "NASA launched the Mars Exploration Rover mission specifically to check whether at least one part of Mars ever had a persistently wet environment that could possibly have been hospitable to life. Today we have strong evidence for an exciting answer: Yes."

 

[55] These and many other shapes were independently found by many researchers, we would like to acknowledge Michael Davidson and Francisco J. Oyarzun.

[56] P.R. Christensen et al (2000) “THE DISTRIBUTION OF CRYSTALLINE HEMATITE ON MARS FROM THE THERMAL EMISSION SPECTROMETER: EVIDENCE FOR LIQUID WATER” Lunar and Planetary Science XXXI 1627.pdf.

Crystalline hematite has been mapped over an area in Sinus Meridiani approximately 500 km in longitude extending approximately 200 km in latitude [3]. The extent of this deposit very closely matches the geomorphic boundary of a smooth, layered, friable unit that is interpreted to be sedimentary sedimentary in origin [3, 9]. This material may be the uppermost surface in the region, indicating that it

might be a later-stage sedimentary unit, or alternatively a layered portion of the heavily cratered plains units. A second accumulation of hematite approximately 60 x 60 km in size is observed in Aram Chaos (2° N, 21° W). This site is also associated with layered materials and a water-rich environment.”

[57] M. D. Lane et al (2001) “UPDATE ON STUDIES OF THE MARTIAN HEMATITE-RICH AREAS” LPSC XXXII 1984.pdf.

Figure 4. Crater count diagram and isochrons for the Terra Meridiani hematite-rich area. Filled symbols show the population of "fossil craters" lying near the saturation equilibrium limit (upper straight line), indicating a very ancient surface. Open symbols show the fresh, recent craters created since the modern surface formed, indicating that the area has been exposed for as little as a few million years. Our interpretation is that an ancient (paleolake bed?) was covered by sediments and exhumed only a few million years ago.”

[58] L.R. Gaddis et al  (2003) “MINERAL MAPPING IN VALLES MARINERIS, MARS: A NEW APPROACH TO SPECTRAL DEMIXING OF TES DATA” LPSC XXXIV 1956.pdf.

Mineral abundance maps (Fig. 5) show basaltic lithologies for much of the VM interior, in the form of high- and low-Ca pyroxenes (up to 24% total) and plagioclase minerals (up to 28%) in layered deposits in the walls and interior, as well as in dark materials at the base of canyon walls. Note that the presence of surface dust in parts of Ophir and east Candor Chasmata appears to decrease the apparent abundance of minerals in these areas. The distribution of gray hematite agrees well with previous results [18], but we see only (~8%) a small enrichment of red hematite in the possible hydrothermal site in west Candor [14] (Fig. 6).”

[59] F. S. Anderson et al (2003) “MINERALOGY OF THE VALLES MARINERIS FROM TES AND THEMIS” Sixth International Conference on Mars (2003) 3280.pdf.

 Our observations of hematite in the VM are similar to those seen by Christensen et al., [37].”

[60] D. C. Catling and C. P. McKay (2000) “Aqueous Iron Chemistry on Early Mars: Was it Influenced by Life?” Journal of Conference Abstracts Volume 5(2), 291.

http://camb.demonhosting.co.uk/JConfAbs/5/291.pdf

The Thermal Emission Spectrometer on NASA's Mars Global Surveyor has detected deposits of crystalline hematite [1] in Sinus Meridiani, Aram Chaos and Vallis Marineris. These appear to be similar to terrestrial iron formations that formed in the Earth's Pre-cambrian oceans. The Sinus Meridiani deposit

exceeds ~105km2 in size, and consists of coarse-grained, grey, schistose hematite [2]. Its age is ~4Ga or older based on counts of exhumed fossil craters [3]. Terrestrial Banded Iron Formations (BIFs) are laminated sediments deposited directly from solution. Pathological cases of crystalline hematite are

particularly characteristic of the Late Proterozoic. These are associated with glaciomarine deposits and possibly formed when oceanic ice cover retreated. Iron oxides were precipitated when ferrous iron reacted with dissolved O2. There is no question that the oxygen in the late Proterozoic atmosphere originated

from photosynthetic organisms. Could iron formations that formed ~4 Ga ago on Mars also be related to oxygenic photosynthesis?

On early Mars several mechanisms could precipitate iron oxides from solution. However, these processes all stoichiometrically require oxygen. There are only two possibilities for an oxygen source: (1) Small quantities of oxygen were slowly produced as hydrogen escaped to space and ferrous iron acted as a sink for this oxygen over an extended timescale.

(2) Early Mars had an oxygenic photosynthetic biosphere. Simple calculations suggest that atmospheric oxygen was very scarce on a volcanically active early Mars. The exposed deposits of hematite, if they are deep, would require significant quantities of oxygen. Finally, although many of the findings

suggestive of life in the ALH84001 meteorite have been disputed, the strongest piece of evidence has always been magnetite crystals of biogenic shape. It is interesting to note that magneto-tactic bacteria use magnetite for a specific purpose: to move along a redox gradient away from a surface environment dominated by oxygen.”

 

[61] C.S Cockell (2003) “LIFE IN MARTIAN SNOWS – MEASUREMENTS OF UV PROTECTION UNDER NATURAL ANTARCTIC SNOWS IN THE UVC (254 nm)” Third Mars Polar Science Conference  6125.pdf.

Convolved with a simple Mars radiative transfer model, the data suggests that under ~6 cm of Martian

snow, DNA-damage would be reduced by an order of magnitude [2]. Under approximately 30 cm of snow,

DNA damage would be no worse than that experienced at the surface of the Earth. Although we do not

know the exact characteristics of Martian snows, these first-order data suggest that burial in even modest coverings of Martian snows could allow for the long-term survival (and if water if present, even growth) of contaminant microorganisms at the Martian polar caps even under the extreme UV fluxes of clear Martian

skies. These coverings of snow will also allow for enhanced preservation of organics against UVdegradation. Intriguingly, at the depth at which DNA damage is reduced to similar levels as those found on the surface of present-day Earth, light levels in the photosynthetically active region (400 to 700 nm) are still two orders of magnitude higher than the minimum required for photosynthesis, showing that within snow-pack on planets lacking an ozone shield, including Mars, UV damage can be mitigated, but light levels are still high enough for organisms that have a requirement for exposure to light for their energy needs. Photosynthetic life is not expected at the Martian poles, but the data reveal the apparently favourable radiation environment for life within the polar caps.”

 

[62]  B. M. Hynek and R. J. Phillips (2001) “Evidence for extensive denudation of the Martian highlands” Geology, 29, 407-410.

Using high-resolution topographic data from the Mars Orbiter laser altimeter (MOLA) instrument on the Mars Global Surveyor mission (Smith et al., 1999), we have gathered evidence for a major fluvial

resurfacing event in the Martian highlands. We completed detailed geomorphic mapping for the Margaritifer Sinus region (08–308S, 08–308W), where resurfacing appears most evident. In addition, evidence from adjacent areas suggests that this was not a localized event, but one that affected at least 1 3 107 km2 (an area equivalent to the European continent) of the cratered uplands. The topographic information allows for the first time a separation of younger, low-standing fluvially reworked terrains from older, high-standing erosional remnants. The newly acquired MOLA data also allow the volume of eroded material to be sensibly determined and minimum erosion rates to be estimated. The erosional episode was limited in time to no more than several hundred million years, and occurred ca. 4 Ga. The scale of the processes involved strongly suggests, but does not demonstrate uniquely, that precipitation must have played a major role in landscape denudation in this region of Mars.”

[63]Mars Exploration Rover Mission Press Releases (April 15, 2004). Available online at:

 http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20040415a.html

NASA's Opportunity rover has examined an odd volcanic rock on the plains of Mars' Meridiani Planum region with a composition unlike anything seen on Mars before, but scientists have found similarities to meteorites that fell to Earth.

"We think we have a rock similar to something found on Earth," said Dr. Benton Clark of Lockheed Martin Space Systems, Denver, science-team member for the Opportunity and Spirit rovers on Mars. The similarity seen in data from Opportunity's alpha particle X-ray spectrometer "gives us a way of understanding 'Bounce Rock' better," he said. Bounce Rock is the name given to the odd, football-sized rock because Opportunity struck it while bouncing to a stop inside protective airbags on landing day.

The resemblance helps resolve a paradox about the meteorites, too. Bubbles of gas trapped in them match the recipe of martian atmosphere so closely that scientists have been confident for years that these rocks originated from Mars. But examination of rocks on Mars with orbiters and surface missions had never found anything like them, until now.

"There is a striking similarity in spectra," said Christian Schroeder, a rover science-team collaborator from the University of Mainz, Germany, which supplied both Mars rovers' Moessbauer spectrometer instruments for identifying iron-bearing minerals.”

[64] WILLIAM I. AUSICH, et al. J. Paleont., 76(6), 2002, pp. 975–992 Copyright q 2002, The Paleontological Society “0022-3360/02/0076-975 “ORDOVICIAN [DOBROTIVIAN (LLANDEILLIAN STAGE) TO ASHGILL] CRINOIDS (PHYLUM ECHINODERMATA) FROM THE MONTES DE TOLEDO AND SIERRA MORENA, SPAIN WITH IMPLICATIONS FOR PALEOGEOGRAPHY OF PERI-GONDWANA”

 

[65] R. B. ARONSON, AND D. B. BLAKE (2001) “Global Climate Change and the Origin of Modern Benthic Communities in Antarctica” AMER. ZOOL., 41:27–39, Figures 1 and 3b.

 

[66]U. RADWA¡SKA & A. RADWA¡SKI (2003) “The Jurassic crinoid genus Cyclocrinus D’ORBIGNY, 1850: still an enigma” Acta Geologica Polonica, Vol. 53 (2003), No. 4, pp. 301-320 Figures 3, 8, 9, 10, 11, 12, 13, and 14.

http://www.geo.uw.edu.pl/agp/table/pdf/53-4/radwanscy.pdf

 

 

 

[67] JPL (2004) Mars Exploration Rover Mission raw images.  m/030/1M130846496EFF0454P2933M2M1

[68]JPL (2004) Mars Exploration Rover Mission raw images.   m/034/1M131201699EFF0500P2933M2M1

[69] R. T. SCHELBLE et al (2001) “HEMATITE MINERALIZED BACTERIAL REMNANTS: IMPLICATIONS FOR MARTIAN HEMATITE DEPOSITS” LPSC XXXII 1438.pdf.

by Fe-oxides for extended periods of time. Although

banded iron formations have not so far been recognized

on Mars, hematite deposits have been observed.

Christensen, et al. [7] cite five possibilities for the origin

of the hematite deposits:

· Direct precipitation from standing, oxygenated

iron-rich water

· Precipitation from iron-rich hydrothermal fluid

· Low-temperature dissolution and precipitation

through mobile groundwater leaching

· Surface weatherings and coatings

· Thermal oxidation of magnetite-rich lavas

If bacteria did exist on Mars, their preservation by

Fe-oxides in any of these potential settings is possible.

Thus, the Martian hematite deposits would be an

excellent site to look for past life on Mars.

 

[70]JPL (2004) Mars Exploration Rover Mission raw images. m/029/1M130761497EFF0454P2953M2M1.JPG

[71] A. Krasnopolsky et al. “DETECTION OF METHANE IN THE MARTIAN ATMOSPHERE: EVIDENCE FOR LIFE” V. European Geosciences Union 1st General Assembly, Nice, France, 25 - 30 April 2004. Available online at:  http://www.cosis.net/abstracts/EGU04/06169/EGU04-A-06169.pdf

Using the Fourier Transform Spectrometer at the Canada-France-Hawaii Telescope, we observed a spectrum of Mars at the P-branch of the strongest CH4 band at 3.3 µm with resolving power of 220,000. Summing up the spectral intervals at the expected positions of 18 strongest Doppler-shifted martian lines, we detected the absorption by martian methane at a 3.9 sigma level. The observed CH4 mixing ratio is 11 ± 4 ppb. Total photochemical loss of CH4 in the martian atmosphere is equal to 1.8×105 cm2 s1, and the CH4 lifetime is 440 years. Heterogeneous loss of atmospheric methane is probably negligible, while the sink of CH4 during its diffusion through the regolith may be significant. There are no processes of CH4 formation in the atmosphere, so the photochemical loss must therefore be balanced by abiogenic and biogenic sources. The mantle outgassing of CH4 is 4000 cm2 s1 on the Earth and smaller by an order

of magnitude on Mars. The calculated production of CH4 by cometary impacts is 2.3 per cent of the methane loss. Methane cannot originate from an extinct biosphere, as in the case of “natural gas” on Earth, given the exceedingly low limits on organic matter set by the Viking landers and the dry recent history which has been extremely hostile to the macroscopic life needed to generate the gas. Therefore, methanogenesis by living subterranean organisms is the most likely explanation for this discovery. Our

estimates of the biomass and its production using the measured CH4 abundance show that the martian biota may be extremely scarce and Mars may be generally sterile except for some oases.

[72] Kerr (2004)Methane Means Martians?”, ScienceNOW 2004: 1.

 

 

[73] M. J. Mumma et al (2003)“[14.18] A Sensitive Search for Methane on Mars.”  DPS 35th Meeting, 1-6 September 2003 Session 14. Mars Atmosphere II Poster, Highlighted on, Wednesday, September 3, 2003, 3:00-5:30pm, Sierra Ballroom I-II.

CH4 and its oxidation products (H2CO, CH3OH, C2H6) on Mars have received both observational (1) and theoretical attention (2, 3), but have not been firmly detected. Owing to its short photochemical lifetime (~ 300 years), the existence of significant methane would indicate \underline{recent} release from sub-surface reservoirs; a quantitative measure of the release rate could be inferred from its present atmospheric abundance. Sub-surface methane could be primordial (reduced cosmogonic carbon) (1) or biotic in origin (4); local enhancements are expected if methane is released from discrete regions. The presence of sub-surface hydrogen concentrations on Mars has been inferred from local-enhancements in epithermal neutron fluxes measured on Mars Odyssey (5), however, independent evidence is required to establish its likely chemical form (e.g., water vs. hydrocarbons) in low-latitude sites (Amazonia Planitia, and Schiaparelli-Cassini). We suggest that enhanced methane there could test whether sub-surface hydrogen is chemically bound in hydrocarbon moieties. In any case, a quantitative measure of methane production would provide a key for assessing models of biogenic vs. primordial origins. “