Mars May Not Have Had Liquid Water Long Enough For Life To Form

Elizabeth Rayne reports via Ars Technica: Led by planetary researcher Lonneke Roelofs of Utrecht University in the Netherlands, a team of scientists has found that the sublimation of CO2 ice could have shaped Martian gullies, which might mean the most recent occurrence of liquid water on Mars may have been further back in time than previously thought. That could also mean the window during which life could have emerged and thrived on Mars was possibly smaller. 'Sublimation of CO2 ice, under Martian atmospheric conditions, can fluidize sediment and creates morphologies similar to those observed on Mars,' Roelofs and her colleagues said in a study recently published in Communications Earth & Environment.

To recreate a part of the red planet's landscape in a lab, Roelofs built a flume in a special environmental chamber that simulated the atmospheric pressure of Mars. It was steep enough for material to move downward and cold enough for CO2 ice to remain stable. But the team also added warmer adjacent slopes to provide heat for sublimation, which would drive movement of debris. They experimented with both scenarios that might happen on Mars: heat coming from beneath the CO2 ice and warm material being poured on top of it. Both produced the kinds of flows that had been hypothesized. For further evidence that flows driven by sublimation would happen under certain conditions, two further experiments were conducted, one under Earth-like pressures and one without CO2 ice. No flows were produced by either. 'For the first time, these experiments provide direct evidence that CO2 sublimation can fluidize, and sustain, granular flows under Martian atmospheric conditions,' the researchers said in the study.

Because this experiment showed that gullies and systems like them can be shaped by sublimation and not just liquid water, it raises questions about how long Mars had a sufficient supply of liquid water on the surface for any organisms (if they existed at all) to survive. Its period of habitability might have been shorter than it was once thought to be. Does this mean nothing ever lived on Mars? Not necessarily, but Roelofs' findings could influence how we see planetary habitability in the future.

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