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The uncertainty of science: New research suggests that, in general, Mars has always been too cold to harbor liquid water on its surface for long periods.
Mars’ atmosphere was probably never thick enough to keep temperatures on the planet’s surface above freezing for the long term, suggests research published today in Nature Geoscience1. Although the planet’s topography indicates that liquid water has flooded Mars in the distant past, evidence increasingly suggests that those episodes reflect occasional warm spells, not a consistently hospitable phase of the planet’s history.
The research does not say that liquid water never flowed on the Martian surface, only that such events were short-lived. They looked at craters and noted that the surface has impacts from meteorites that would not have survived to the surface had the atmosphere been thick enough for liquid water.
The research however did not address Mars’ relatively smooth northern hemisphere, where there are not a lot of craters and where some scientists think there might once have been a shallow ocean. If Mars never had liquid water for long periods, why does this area lack craters?