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The uncertainty of science: New modeling suggests that the wet gullies seen on Mars can be produced by dry ice, not water.
The theory is not completely new, but Cedric Pilorget and François Forget, with the University of Paris-Sud, and Paris’ Pierre and Marie Curie University, respectively, flesh out the idea with some hard numbers. Their new computer model calculates seasonal changes and impacts of an underlying layer of regolith, a carbon dioxide ice layer and the carbon dioxide-dominated gas atmosphere above. The simulation can take into account a variety of latitudes, slopes and other parameters.
The scientists found that most of the gullies could be created in a process that does not require any liquid water.