Repost by
Philip Simon
Mars Cataclysmic Epoch - A pyrospeculation.
Wed Mar 24, 2004 10:36
12.45.169.2

Evidence for Martian Seas was pretty overwhelming even before the MER maids. Dr. Malin's site shows good images that indicate the Valles Marineris contains sedimentary rock from top to bottom. Possibly more than 10,000 feet of it, and formed of regularly spaced beds. That, and lateral continuity, and sedimentary layers found throughout large regions and as domed features in craters argues strongly that these are not just remnants of temporary lakes filling the valley as is often claimed, but are in fact the remnants of vast oceans on a geologically active planet.
Mars orbital position alone suggests that it would have had relatively more water and other lighter elements than Earth, thus even planet wide oceans are a possibility in the early geologic periods of Mars.

But what of the later period, when the oceans dried out, likely the result of the loss of the shielding effects of the magnetic field as the core eventually cooled and differential internal rotation ceased. This period shows evidence of unusual cataclysmic flooding, valleys that pop up from no where and just end in craters, plains, or holes without much "fanfare." I agree that these regions show evidence of cataclysmic flooding, but not of any sustained periods of rainfall. The tributary systems are not well developed enough.

Many theories have been proposed, but I will just jump to my short speculation after this long intro.

I propose that during the marine periods on Mars, life existed and produced organic deposits such as methane hydrate or coal. As the oceans dried up, evaporites would deposit. The last to deposit would be the most soluble salts, such as Nitrates. Mars was rich in light elements, and dry enough, and cold enough, to produce beds of oxidizing salts that could never have formed on Earth. Faulting may have brought these oxidizing Nitrates, Sulfates, and possibly Sulfuric acid in contact with reduced forms of biologically deposited Carbon. Alternatively, these beds may also have just been close stratigraphically, or mixed together. Once the oceans were gone, these beds would be exposed to the atmosphere, which may have still contained substantial oxygen at that time. It would also expose these beds to lightning strikes. These may have promoted ignition of carbonaneous biologic deposits which would burn underground. These underground fires may have been much more rapid than those on Earth due to the oxidizers present, and/or very flammable methane hydrates as fuel. This would, in turn, rapidly melt large areas of permafrost, destabilize the ground with collapses that would then provide more fuel and oxidizers in an accelerating process and unleash a regional deluge. The increase in water vapor would provide an atmospheric pressure adequate for rain for periods of time, but the last big burns would provide a last hurrah. After that, smaller burns would just cause the surface to melt and the water would rapidly boil away, leaving salts, some brines that might flow a little, and lots of collapse holes. Other competing theories such as impacts or volcanic episodes have difficulty explaining the widespread regional nature of many of these deluges. The small apparent former rivers that flow into holes are explained well by the subterranean burning theory. Meteorite impacts could also have exposed these flammable beds and provided heat for ignition.

An alternative, non biologic fuel such as bedded deposits of Iron or Magnesium sulfide also seems like a good possibility. Iron sulfide deposits burn on Earth. Mars could have had an early reducing atmosphere rich in H2S which would have been consumed by the precipitation of sulfides as any free heavy metal ions became available in the early oceans. The later deposition of oxidizing Sulfates and possibly Nitrates would have been an unstable mix once the oceans were gone. Flame on, Mars pyrocataclysmic microbes!