Russia, starting back when it was the USSR, was the first to try to send a probe to Mars, in 1960, but it remains 1 for 19 in attempts that were fully successful. The Russians are the only ones to have successfully landed probes on Venus, so their poor track record for Mars remains something of an enigma.
The US has fared better with its missions to Mars. It enjoys a 73 percent success rate over the course of 19 launches, with craft typically far outlasting their initial "warranty." NASA's rover Opportunity, for instance, arrived at Meridiani Planum, just south of the Martian equator, Jan. 25, 2004, and it's still exploring its patch of the red planet.
Its primary mission was slated for just over 90 days. Opportunity's twin, Spirit, was supposed to be another 90-day wonder, but it soldiered on for six years before falling silent.
The last decade's worth of missions to Mars have been framed in three words: "follow the water" – the search for past or present evidence of a fluid deemed essential for organic life. But the effort also has contributed to a more sophisticated grasp of the birth and evolution, not only of Mars, but of all the planets in the solar system over its 4.6 billion-year history.
Initially, the notion was that the terrestrial or inner planets "all started out with the same brownie mix," says Darby Dyar, a planetary geologist at Mount Holyoke College in South Hadley, Mass., and a member of Curiosity's science team.