Exploration of Mars
The Viking program launched "Viking 1" and "Viking 2" spacecraft to Mars in 1975; The program consisted of two orbiters and two landers – these were the first two spacecraft to successfully land and operate on Mars.
The primary scientific objectives of the lander mission were to search for biosignatures and observe meteorologic, seismic and magnetic properties of Mars. The results of the biological experiments on board the Viking landers remain inconclusive, with a reanalysis of the Viking data published in 2012 suggesting signs of microbial life on Mars.
The Viking orbiters revealed that large floods of water carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers. Areas of branched streams, in the southern hemisphere, suggest that rain once fell.
List of artificial objects on Mars
The following table is a partial list of artificial objects on the surface of Mars, consisting of spacecraft which were launched from Earth. Most are defunct after having served their purpose, but the "Curiosity" rover and the "InSight" lander are still operational as of 2018. "InSight" is the most recent artificial object to land safely on Mars. The table does not include smaller objects, such as springs, fragments, parachutes and heat shields. As of November 5, 2016, there are about 14 spacecraft missions on the surface of Mars: some of these missions have multiple spacecraft.