All eyes are on the NASA rover Curiosity. It is poised to begin drilling into a Martian rock soon.
There's less attention being paid to another Mars rover -- Opportunity. The older rover is quietly embarking on its tenth year of exploration.
Compared to Curiosity, Opportunity is smaller and doesn't carry the same high-tech tools. But since landing in January 2004, it has made many discoveries including that Mars was once warmer and wetter than today.
Opportunity and its twin Spirit were only supposed to explore for three months, but both outlasted their original mission. Opportunity remains healthy and is studying interesting rocks in a massive crater. Spirit lost communication with Earth in 2010 shortly after getting stuck in Martian sand.