Meridiani Planum interests scientists
because it contains an ancient layer of hematite, an iron oxide that, on Earth, almost always forms in an environment containing liquid water. The site appears dry now. So how did the hematite get there? Was there once water in the area? If so, where did it go?
http://science.nasa.gov/headlines/y2004/22jan_meridianiplanum.htm?list157044
NASA