The Solar System

The Inner Solar System

What evidence have we gathered from the Martian surface to show there was once liquid water on Mars?

The Mars Exploration Rovers Spirit and Opportunity are geological robots that have explored several areas of Mars. Among the many discoveries made with them are minerals that form only in the long-term presence of water; microscopic mineral structures nicknamed “blueberries” that only form when moisture is present; and certain kinds of clay, gypsum and other substances in Martian rocks that would have formed only if liquid water had been in the environment. The strong scientific conclusion is that Mars is currently dry on its surface, but that this was not always the case. It may even have been awash with liquid water billions of years ago.


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