As the world rang in the Near Year this this week, NASA was looking forward to a big milestone of its own - nine years and counting on the surface of Mars for an overachieving Red Planet rover mission.
The golf-cart-size Spirit rover landed on Mars on Jan. 3, 2004, PST. Its twin, Opportunity, touched down at another Martian locale three weeks later, joining Spirit on a 90-day quest to search for signs of past water activity on the Red Planet. Together, the two robots make up the Mars Exploration Rover mission, the precursor to the huge Mars rover Curiosity, which arrived at the planet last August.
The two NASA robots found plenty of such evidence, helping scientists confirm that Mars - now a frigid and seemingly bone-dry place - was warmer and wetter billions of years ago. Spirit even stumbled onto an ancient hydrothermal system, where heat energy and liquid water may have created conditions capable of supporting life as we know it.
Both rovers kept on chugging long after their warranties expired. Spirit finally stopped communicating with Earth in March 2010 and was declared dead a year later. Opportunity is still going strong, exploring clay deposits on the rim of Mars' Endeavour Crater.