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.
