Space/Science — HabitableZone

Space/Science » in reply to regular strata and the periodicity of cometary impact

Impact history
Philip Simon — (archived)

If the episodic impacts occurred every 26 million years, then in 4 billion years there would be only about 150 cataclysmic layers. I think more layers than that have been seen, even from satellite. On the small scale, Meridiana rocks have layer upon layer in the mm scale - possibly many millions of layers in total. The preponderance of evidence (epsomite and other highly hydrated minerals, etc) indicates that these are not volcanic or cataclysmic deposits. Only sedimentary processes (including aeolian) seem likely to account for this, and aqueous processes most likely. That water could, however, have been highly acidic. Any volcanism or impacts that penetrated evaporites would have released much acid gases and water vapor.

The proximity of Mars to the asteroid belt must surely have caused many cataclysms in the past, in particular shortly after the breakup of the large body or bodies that were the precursors of today's "swept clean" asteroid belt. (I favor the theory that the Belt is a wrecked planet, not planet wanna be.) The Mars crossing asteroids must have been quite numerous and multi-episodic after the Planet 5 destruction.

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