Twin rovers on opposite sides of the Red Planet have found additional evidence that liquid water once flowed there, scientists announced last week during a telephone briefing. Designed to last only 3 months, the rovers have been reporting data back to Earth since January (see "Martian water everywhere," in this week's issue: Martian water everywhere).
On the southwestern slope of the shallow, stadium-size crater in which it landed, the rover Opportunity has found that several flat rocks bear a geometric network of fractures. The fractures resemble mud cracks on Earth, which form when water-soaked soil dries and contracts, notes rover researcher John Grotzinger of the Massachusetts Institute of Technology.
Opportunity had found evidence that a body of stan