The first successful fly-by of Mars was on July 14--15, 1965, by NASA's Mariner 4. On November 14, 1971 Mariner 9 became the first space probe to orbit another planet when it entered into orbit around Mars.The first objects to successfully land on the surface were two Soviet probes: Mars 2 on November 27 and Mars 3 on December 2, 1971, but both ceased communicating within seconds of landing. The 1975 NASA launches of the Viking program consisted of two orbiters, each having a lander; both landers successfully touched down in 1976. Viking 1 remained operational for six years, Viking 2 for three. The Viking landers relayed color panoramas of Mars and the orbiters mapped the surface so well that the images remain in use.
The Soviet probes Phobos 1 and 2 were sent to Mars in 1988 to study Mars and its two moons. Phobos 1 lost contact on the way to Mars. Phobos 2, while successfully photographing Mars and Phobos, failed just before it was set to release two landers to the surface of Phobos.
Following the 1992 failure of the Mars Observer orbiter, the NASA Mars Global Surveyor achieved Mars orbit in 1997. This mission was a complete success, having finished its primary mapping mission in early 2001. Contact was lost with the probe in November 2006 during its third extended program, spending exactly 10 operational years in space. The NASA Mars Pathfinder, carrying a robotic exploration vehicle Sojourner, landed in the Ares Vallis on Mars in the summer of 1997, returning many images.
The NASA Phoenix Mars lander arrived on the north polar region of Mars on May 25, 2008. Its robotic arm was used to dig into the Martian soil and the presence of water ice was confirmed on June 20. The mission concluded on November 10, 2008 after contact was lost.
The Dawn spacecraft flew by Mars in February 2009 for a gravity assist on its way to investigate Vesta and then Ceres.
Spirit Rover (MER-A) was active from 2004 until 2010, when it stopped sending data.
Current missionsThe NASA Mars Odyssey orbiter entered Mars orbit in 2001. Odyssey's Gamma Ray Spectrometer detected significant amounts of hydrogen in the upper metre or so of regolith on Mars. This hydrogen is thought to be contained in large deposits of water ice.
The Mars Express mission of the European Space Agency (ESA) reached Mars in 2003. It carried the Beagle 2 lander, which failed during descent and was declared lost in February, 2004. In early 2004 the Planetary Fourier Spectrometer team announced the orbiter had detected methane in the Martian atmosphere. ESA announced in June 2006 the discovery of aurorae on Mars.
In January 2004, the NASA twin Mars Exploration Rovers named Spirit (MER-A) and Opportunity (MER-B) landed on the surface of Mars. Both have met or exceeded all their targets. Among the most significant scientific returns has been conclusive evidence that liquid water existed at some time in the past at both landing sites. Martian dust devils and windstorms have occasionally cleaned both rovers' solar panels, and thus increased their lifespan.
On March 10, 2006, the NASA Mars Reconnaissance Orbiter (MRO) probe arrived in orbit to conduct a two-year science survey. The orbiter will map the Martian terrain and weather to find suitable landing sites for upcoming lander missions. The MRO snapped the first image of a series of active avalanches near the planet's north pole, scientists said March 3, 2008.
The joint Russian and Chinese Phobos-Grunt mission to return samples of the Martian moon, Phobos, launched in 2011. The spacecraft missed its opportunity to enter an orbit that would bring it to Mars, so it has failed its planned mission.
En routeThe Mars Science Laboratory, named Curiosity, launched on 26 November, 2011, and plans reach Mars in August 2012. It is larger and more advanced than the Mars Exploration Rovers, with a movement rate of 90 m/h. Experiments include a laser chemical sampler that can deduce the make-up of rocks at a distance of 13 m.
Future missionsIn 2008, NASA announced MAVEN, a robotic mission in 2013 to provide information about the atmosphere of Mars. In 2018 the ESA plans to launch its first Rover to Mars; the ExoMars rover will be capable of drilling 2 m into the soil in search of organic molecules.
The Finnish-Russian MetNet, is mission concept where multiple small vehicles on Mars to establish a widespread observation network to investigate the planet's atmospheric structure, physics and meteorology. MetNet was considered for a piggyback launch on the Russian Phobos-Grunt mission, but not selected.