Two US space probes to Mars, each of which consisted of an orbiter and a lander (see table). The orbiters studied the planet and its satellites, while the landers photographed the surface around them, took weather readings, and analysed the composition of the soil. Of particular interest was the possible presence of living organisms on Mars, but none were found.
1975 August 20
Entered orbit around Mars 1976 June 19; lander descended in Chryse Planitia 1976 July 20
1975 September 9
Entered orbit around Mars 1976 August 7; lander descended in Utopia Planitia 1976 September 3
Subjects: astronomy and cosmology.