LOS ANGELES - The Mars rover Spirit marks its seventh year on the red planet Monday. Not only is it stuck in a sand trap, it hasn't communicated with Earth since March.
NASA doesn't know whether Spirit is dead, but the space agency is diligently listening for it. A pair of Mars orbiters has been making daily overhead passes hoping for a signal from Spirit, which became mired in sand in April 2009.
Meanwhile, its twin, Opportunity, is exploring a 300-foot (90-meter)-diameter crater and will move onto another target in several months.
