The Mariner Mars 7 mission was planned to consist of two spacecrafts on complementary
missions, but due to the failure of Mariner 8 to launch properly, only one spacecraft was
available. Mariner 9 combined mission objectives of both Mariner 8 (mapping 70 % of the
Martian surface) and Mariner 9 (a study of temporal changes in the Martian atmosphere and
on the Martian surface). For the survey portion of the mission, the planetary surface was
to be mapped with the same resolution as planned for the original mission, although the
resolution of pictures of the polar regions would be decreased due to the increased slant
range. The variable features experiments were changed from studies of six given areas
every 5 days to studies of smaller regions every 17 days. Mariner 9 arrived at Mars on
November 14, 1971. The spacecraft conducted many experiments,
gathering data on the atmospheric composition, density, pressure, and temperature and also
the surface composition, temperature, and topography of Mars. In addition, it took
various images. After depleting its supply of
attitude control gas, the spacecraft was turned off October 27, 1972.