Planetary Protection at NASA
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Missions That Explore Our Solar System

Mars Climate Orbiter

Illustration of Mars Climate Orbiter
Illustration of Mars Climate Orbiter – NASA/JPL

Mars Climate Orbiter (MCO), launched Dec. 11, 1998, was intended to function as an interplanetary weather satellite and a communications relay for the Mars Polar Lander. The MCO mission was classified Category III for planetary protection purposes. NASA lost contact with the MCO spacecraft on Sept. 23, 1999, upon its arrival at Mars. Though the cause of the loss of MCO is not certain, the spacecraft most likely inadvertently entered the atmosphere of Mars and probably burned up during entry. If, instead, MCO survived entry to impact the surface of Mars, the debris could pose the possibility of forward contamination. For more information on Mars Climate Orbiter, see this page at the Science Mission Directorate website.