A Cosmic Blunder

September 23, 1999 - After a 9-month journey through space, NASA’s Mars Climate Orbiter was about to glide gracefully into orbit around the Red Planet on this day. Instead, the $125 million probe vanished in a puff of silence — all because of a simple math mistake.

The spacecraft’s mission was ambitious: study the Martian atmosphere and serve as a communications relay for the upcoming Mars Polar Lander. But as engineers prepared to celebrate the successful orbital insertion burn, the orbiter never re-emerged from behind Mars. It had dipped far too low into the planet’s thin atmosphere and probably burned up or skittered off into space.

What the hell happened? The truth is painfully embarrassing. Lockheed Martin engineers had provided thruster data in pound-seconds (imperial units), while NASA’s Jet Propulsion Laboratory assumed the numbers were in newton-seconds (metric). The error compounded during the cruise to Mars, and by the time the spacecraft arrived, it was tens of kilometers off course.

As NASA’s Richard Cook admitted afterward:

“Everyone was amazed we didn’t catch it. The units thing became the joke — but no one was laughing when we lost the spacecraft.”

It was a sobering reminder that even in the space age, a single conversion slip could bring down an entire mission. The Mars Climate Orbiter became a case study in engineering schools worldwide — forever remembered as the spacecraft lost to a metric-imperial mismatch.