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Carbonated Mars NASA Science

A common substance found in ordinary classroom chalk could hold the key to a puzzle of planetary proportions: the mysterious whereabouts of water on Mars. The brittle, white material in chalk –a form of carbonate– may seem rather ordinary, but finding carbonates on Mars would have some extraordinary implications. The discovery would provide strong evidence that liquid water once flowed on the Red Planet. Such carbonates might also harbor the fossils of ancient Martian bacteria.