U.S. Orbiters
Mariner 9:
Mariner 9 arrived at Mars on November 3, 1971. This was
the first US spacecraft to enter an orbit around a planet other than the
Moon. At the time of its arrival a huge dust storm was in progress on the
planet. Many of the scientific experiments were delayed until the storm
had subsided. The first hi-resolution images of the moons Phobos
and Deimos were taken from Mariner 9. River and
channel like features were discovered. Mariner 9 mapped a large fraction
of the Martian surface and studied temporal changes in the Martian atmosphere.
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 spacecraft gathered data on the atmospheric composition,
density, pressure, and temperature and also the surface composition, temperature,
and topography of Mars. After depleting its supply of altitude control gas,
the spacecraft was turned off October 27, 1972.
Viking 1:
Viking 1 was based on the design of the
Mariner spacecraft. They consisted of an orbiter and lander. The orbiter
weighed 900 kg and the lander 600 kg. Viking 1 went into orbit about Mars
on June 19, 1976. It monitored the Martian weather. The orbiters mapped
the planet's surface, acquiring over 52,000 images. Viking 1 orbiter was
deactivate on August 7, 1980 when it ran out of altitude-control propellant.
The Viking orbiter took this amazing photo of the "Face on Mars"
(right).
Viking
2: 
Viking
2 was based on the design of the Mariner spacecraft. They consisted of an
orbiter and lander. The orbiter weighed 900 kg and the lander 600 kg. Viking
2 went into orbit about Mars on July 24, 1976. The lander touched down on
August 7, 1976, at Utopia Planitia. The landers had experiments to search
for Martian micro organisms. The results of these experiments are still
being debated. The lander provided detailed, color, panoramic views of the
Martian terrain. They also monitored the Martian weather. The orbiters mapped
the planet's surface, acquiring over 52,000 images. Viking 2 orbiter was
deactivated on July 25, 1978, when it ran out of altitude-control propellant.
Viking 2 lander used Viking 1 orbiter as a communications relay and had
to be shut down at the same time as the orbiter on August 7, 1980. Viking
2 orbiter took more pictures of the "Inca City" (upper left) and
the "Face on Mars."
!!!!!!!!FIRST IMAGE FROM MARS GLOBAL SURVEYOR!!!!!!!!!
Mars Global Surveyor: The basic spacecraft design is copied from the failed Mars Observer. Global Surveyor will continue to map the surface, including the polar region, at the hightest resolution ever.
