Mars Climate Orbiter
Date: 23 Sep 1999
Mars Climate Orbiter mission was to study Mars from orbit with cameras and atmospheric instruments. It also was designed to serve as a communications relay for the Mars Polar Lander and Deep Space 2 probes.
Communications were lost as the spacecraft prepared to enter orbit around Mars. An investigation found the spacecraft burned up in Mars' atmosphere due to a navigation error caused by the failure to translate English units to Metric.
Image Credit: NASA/JPL