Study reduces chances of liquid water on Mars present – 03/17/2024 – Sidereal Messenger

In 2000, an analysis of data collected by NASA’s Mars Global Surveyor probe revealed the formation of certain marks on slopes during the hottest seasons on the planet. At the time, scientists concluded that it was running water on present Mars – an extraordinary discovery. Now a study seems to definitely throw water on this result. Or rather, carbon dioxide.

Lonneke Roelofs, a researcher at Utrecht University in the Netherlands, led the work that demonstrates that water is not needed to explain these mysterious marks. The formations may well be the result of the sublimation (transformation from ice to gas) of carbon dioxide trapped in the Martian subsoil.

In winter on that planet, temperatures drop below -120 degrees Celsius, enough for the famous CO2, the main component of the Martian atmosphere, to freeze. When spring arrives, this underground ice powerfully converts into gas, due to the low atmospheric pressure, which pushes grains of sediment and makes the material flow, forming the traces seen in the orbital images.

This is actually not a new idea, and has already been proposed as an alternative explanation for current-day water flows on Mars – a complicated proposition in itself, given that most of the Martian surface has atmospheric pressure that prevents the persistence of water in a liquid state, even at temperatures suitable for this. It was imagined that these flows had an enormous amount of salts, capable of allowing liquefaction, albeit temporary.

The novelty of the work by Roelofs and his colleagues, published in the journal Communications Earth and Environment, from the Nature group, is the carrying out of experiments in a “Martian chamber”, capable of simulating the planet’s environment in the laboratory, which allowed us to see the phenomenon happen before your eyes. “We observed that debris flows driven by CO2 ice in Martian conditions as efficiently as debris flows driven by water on Earth,” said the research leader.

As a result, the expectation of searching for liquid water – and therefore life – on the red planet ends up being greatly reduced. But it does not invalidate the discovery that large regions of the planet preserve water ice underground (made both by remote detections and by direct excavation of the surface carried out by the Phoenix probe, close to the Martian north pole) nor the results obtained in-situ by several NASA rovers that indicate that Mars has indeed had a wet past. There are minerals in different regions of the planet that bring with them evidence that rocks had direct contact with water, billions of years ago.

How and for how long this was possible is still a mystery. In theory, Mars should have had a denser atmosphere in the past, capable of generating a more powerful greenhouse effect that made it hotter, but there is no evidence to suggest that this was the case. And, of course, as we also don’t know how life originates and how long it takes to emerge, we can’t say whether the process could have happened there as it did here. Further answers on this depend on missions such as sample return missions, currently under development by Americans, Europeans and Chinese.

This column is published on Mondays in print, in Folha Corrida.

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