NASA currently has two rovers wondering around Mars looking at rocks: Spirit
. They recharge their batteries with solar panels and have to shut way down during the Martian winter to conserve energy. As they roll around and kick up dust the solar panels become coated and lose some of their ability to recharge their batteries.
This is exactly what has happened to the Spirit
, its panels are operating at about 50%, but Opportunity
's have apparently been cleaned a couple of times and it is operating at 100% efficiency.
has landed in an area that has beneficial winds, or it has found a full service gas station on Mars.