NASA’s twin rovers, Spirit and Opportunity, landed on Mars on Jan. 3 and Jan. 24, 2004 PST (Jan. 4 and Jan. 25 UTC). The rovers were planned as 90-day missions to search for geological clues regarding environmental conditions on early Mars, and assess whether those environments were conducive to life. Spirit lasted 20 times longer than its original design, concluding its mission on March 22, 2010.