Final answer:
Mars has been studied by spacecraft since the 1960s, beginning with the Mariner 4. Subsequent missions have orbited, landed, and roamed the planet gathering valuable data. No human has visited Mars, but rovers like NASA's Curiosity have successfully operated on the planet.
Step-by-step explanation:
The history of spacecraft exploration of Mars began with the first successful flyby, with the US Mariner 4 in 1965. This mission transmitted 22 photos back to Earth, depicting a surface filled with impact craters. Many noteworthy missions followed, including NASA's Mariner 9 in 1971, which became the first spacecraft to orbit another planet.
Landings on Mars began with the Viking landers in the 1970s. The Mars Pathfinder mission in 1997 placed the first wheeled rover on Mars, offering closer surface exploration. High-resolution photography and evidence of geological activity, including signs of surface water, became significant discoveries of subsequent spacecraft like the Mars Global Surveyor and the Mars Odyssey orbiter. This orbiter discovered large amounts of subsurface hydrogen, likely indicating frozen water.
In terms of human exploration, it's important to note that while no human has stepped foot on Mars, human-made rovers and landers have thoroughly investigated the Mars surface. The most recent and advanced rover, NASA's Curiosity, landed in 2012. It remains one of the most significant milestones in the search for evidence of life and the past habitability of Mars.