RockDoctor's Journal: new mars stuff

Another potential one from Arxiv.

Anoxic Atmospheres on Mars Driven by Volcanism: Implications for Past
Environments and Life

The current atmosphere of Mars is low pressure, but oxidising (largely because water gets split by UV high in the atmosphere, the hydrogen is lost to space but the oxygen (hydroxyl molecules) is heavy enough (has a short enough mean free path) to be retained in the atmosphere ; the iron in the surface rocks turns red (goes to +3 oxidation state). Which is well and good, and well understood. But ... oxygen does horrible things to biochemistry. Ask any SCUBA diver who has read up on the biochemistry of oxygen toxicity. While biological systems can learn how to handle having the poisonous stuff around, it needs a fair amount of biochemical machinery to contain and manage the poison. After a few hundred million years to a billion years, life on Earth managed to learn how to handle it and survived the "Great Oxidation Event". But all serious models for the origin of life on Earth depend on having initially a reducing atmosphere, unlike that of today's planet (and Mars). Mars today has no observed volcanism, but relatively fresh volcanic landforms suggests there is some volcanism from time to time. Impacts can also inject surface material into the atmosphere without active volcanism.

This study describes a model of the influence of volcanism on the oxidation state of the Martian atmosphere. A modest (more than ~0.14cu.km per year, around 1% of Earth's rate) amount of basaltic volcanism would be able to make the current atmosphere reducing, and volcanism was likely to be more common in the past, so the atmosphere of early Mars was probably often reducing, which is generally expected to be a good thing for a local origin of life. Also, an atmosphere which changed between reducing (after a large impact or volcanism) and oxidising (under the continuing influence of solar radiation) might actually stimulate the development of interesting chemistry (a.k.a "life").

Chemical signatures of previous reducing atmospheres which could be measured with current and future Mars rovers are discussed.