SPACE.com -- Discovery Indicates Mars Was Habitable

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SPACE.com -- Discovery Indicates Mars Was Habitable

The presence of large quantities of carbonates, which don't form in conditions hostile to life, indicate that Mars was once benign enough to support life. The green areas in the image are areas that contain carbonates. Much of the Martain surface was also once covered with salt-rich (acidic) water, but carbonates dissolve quickly in acids so extensive areas must have been far less salty, raising the possibility that such areas could have supported life.