Another difference is the approach itself. Other models that discuss volcano-atmosphere reactions on Mars focus on how the planet could be warmed, Sholes said, using outgassed volcanic gasses.
"Yes, you need liquid water, but you also need appropriate conditions for life, and here we are finding that the volcanoes should have changed the atmosphere enough to be more conducive to forming complex bio-important molecules," he said.
If the atmosphere was anoxic, scientists may be able to see the evidence on the ground, even billions of years later. That's because anoxic conditions should alter the types of minerals and rocks that form, allowing for testable predictions for future Mars missions. Examples include minerals made of ferrous iron — such as siderite, or iron carbonate — as well as elemental sulfur.
"Our results show that, given models for volcanic activity, during periods of sustained volcanism, Mars’ atmosphere could easily shift towards reducing and anoxic conditions, thus producing measurable amounts of elemental sulfur deposits," Sholes said.
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He added that elemental sulfur has not been found yet on Mars, but it is a difficult mineral to study.
"The measurement techniques used could actually cause it to breakdown into smaller molecules that could be misidentified," he said.
Two missions are specifically investigating the Martian atmosphere right now. NASA's MAVEN (Mars Atmosphere and Volatile Evolution), which primarily examines atmospheric loss, and the European Space Agency's TGO (Trace Gas Orbiter), which looks at minority molecules in the Martian atmosphere.
Sholes said the atmosphere does not preserve tracers of past reducing conditions, so the current missions would not help us learn directly about past volcanic activity. Their measurements will help refine the atmospheric models used, however.
"Eventually we would like to update the model to test how single eruption events would change the atmosphere and the timescales involved," he added. "Our current model assumes constant volcanic eruptions, which wouldn’t necessarily be the case. If we could test individual eruptions, we could learn how big of an eruption would be required to switch the atmosphere anoxic, and how long that atmosphere would last before it would switch back."
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