Mars, We've Had a Problem

It's the stuff of scary science fiction: a technical glitch forces a sophisticated spacecraft to lose touch with ground control, orphaning it deep in outer space. Yet that's what happened in 1999 when NASA engineers lost contact with the Mars Climate Orbiter as they attempted to place it in Mars's orbit for research. The cause, investigators later found, was that one team was using a program that calculated distance in English units such as inches, feet and pounds, while another team used metric units. The discrepancy led to faulty measurements of the spacecraft's trajectory -- and the sudden demise of an operation that cost more than $655 million.