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I calanchi su Marte formati dal ghiaccio secco?_alt tag

Were the gullies on Mars formed by dry ice?

A study explains how the canals on Mars could have been created by the defrosting of CO2. But the research does not exclude NASA's hypothesis on the role of liquid water

MILAN - Few months have gone by since NASA's announcement: there is still water on Mars, and from time to time it comes to the surface in liquid state and it runs along and digs other traces on the border of various craters. But now a study published on Nature Geoscience proposes an alternative explanation to that of water tracks. The big canals could originate from the melting of dry ice, i.e. by CO2. However, French researchers Francois Forget and Cedric Pilorget, who work at the space astrophysics institute of the University of Paris, stress that their research does not necessarily disprove the work by NASA, as they studied large canals and traces in different areas from those studied by the American space agency.

The study

This French research started when a formation of large canals was observed when the temperature on Mars was too low for water to come out in liquid form, even considering the presence of salts (which lower the freezing temperature). Researchers then directed their attention to thin layers of dry ice and used modelling to verify what might occur to dry ice if it reached the sublimation point, i.e. the temperature at which the solid become directly a gas, without passing through a liquid phase. Data processing demonstrated that dry ice transforms itself in a gas that is able to crack the ground and produce fluxes of gas mixed with debris. A phenomenon that is unlike anything on Earth.

Alternative hypotheses

"However, the sublimation of dry ice cannot be responsible for all gullies present on Mars, but in particularly cold environments, where large canals arise even during winter periods, CO2 must be the main cause of their formation", commented Pilorget. The hypothesis by NASA is therefore not disproved, but was is important to stress is that not all Martian gullies are to be ascribed to the surfacing of saline water, and that maybe not even dry ice can fully explain the phenomenon. As researchers state, "indeed it is possible that a third explanation, or more than three, exists for large Martian channels".

by editorial staff