Posted: Tue, May 22, 2007, 8:27 AM ET (1227 GMT)
One of NASA's twin Mars Exploration Rovers has found what scientists called Monday the strongest evidence to date that liquid water existed on the Martian surface early in the planet's history. The rover Spirit, studying soil in a range of hills located within Gusev Crater, found one sample with a content of 90 percent pure silica. Such a high concentration of silica, scientists said, can only be created in the presence of water. Project scientists are planning additional studies of that patch of soil, dubbed "Gertrude Weise", and surrounding areas. The discovery was made almost by accident: the patch of soil was studied after Spirit dug a deep track in the area created by the rover's one malfunctioning wheel.
