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 missions to minor planets
Spacecraft visits to minor planets have mostly been flybys, and have ranged from dedicated missions to incidental flybys and targets of opportunity for spacecraft that have already completed their missions. The first spacecraft to visit an asteroid was "Galileo", which flew past 951 Gaspra in October 1991; an incidental encounter while the probe was en route to Jupiter. The first dedicated mission was "NEAR Shoemaker", which was launched in February 1996, and entered orbit around 433 Eros in February 2000, having first flown past 253 Mathilde. "NEAR" was also the first spacecraft to land on an asteroid, surviving what was intended to be an impact with Eros at 20:01 on 12 February 2001 at the planned end of its mission. As a result of its unexpected survival, the spacecraft's mission was extended until 1 March to allow data to be collected from the surface.