Viking 2 orbiter shutdown
Less than two years after arriving at Mars, the “mothership” orbiter that delivered the Viking 2 lander to the red planet is permanently shut down. Having lost most of its fuel to a leak, the Viking 2 orbiter can no longer be commanded to change orbit, and is placed in a parking orbit. Without an orbiter to relay its findings to, Viking 2 continues operating on the surface of Mars for two more years, sending data directly to Earth at a lower bit rate.