The Mars Climate Orbiter took off Dec. 11, 1998, on a mission to orbit Mars as the first interplanetary weather satellite. The spacecraft was lost nearly a year later as it entered orbit around Mars.

The problem turned out to be that English units, instead of metric measurements, were used in a software file. As a result, the craft was 170 kilometers too low when it tried to enter orbit. A NASA investigation determined the orbiter either burned up in the Martian atmosphere or was lost in space.