Several NASA missions to Mars, some consisting of two launches. Mars Surveyor ’98, carrying an orbiter and lander, was lost during insertion into Mars orbit. Mars Surveyor 2001, planned for launch in 2001, was cancelled due to cost overruns. Mars Global Surveyor, launched in 2003, reached Mars in 2004; its two rovers, Spirit and Opportunity, were deployed successfully and found evidence of past water.

http://www.windows2universe.org/mars/exploring/MSP_overview.html NASA missions to map and study the climate of Mars.