mars rovers turn 1

Today is either the first or almost-second anniversary of NASA's Opportunity rover's arrival on mars - depending on which planet you base your calendar on. The rover has been on the Red Planet for 687 earth days, or one martian year. The second rover, Spirit, hit the same landmark 3 weeks ago. Their original missions were each scheduled for 90 days.

The rovers represent a giant leap forward in data gathering for planetary science. Among their discoveries include soil and atmospheric composition data, establishing a geological history for Mars, and most importantly finding numerous indicators that liquid water once flowed there - lots of it.