PASADENA, Calif. - NASA plans to crash its $1.5-billion Galileo spacecraft into Jupiter this weekend to make sure it doesn't accidentally contaminate the planet's ice-covered moon Europa with bacteria from Earth.
After Galileo's orbit carries it behind Jupiter at 3:49 p.m. Sunday, the aging probe will plunge into the planet's stormy atmosphere at a speed of nearly 108,000 mph.Its suicide dive comes at the end of its 35th orbit of the planet - far longer than the 11 orbits planned for the spacecraft.
The heat generated as it streaks through the atmosphere will vaporize the nearly 3,000-pound Galileo and any microbes that may have been stowaways on the craft since its 1989 launch.
The crash will ensure Galileo doesn't hit Europa and spill bacteria onto the ice that caps its enormous oceans.
Europa, a planet-sized moon, is widely believed to have the most promising habitat for extraterrestrial life within the solar system. Were Earth bugs to gain a toehold on Europa, they could compromise future attempts to probe the moon for indigenous life.
"It seems like a good place where, potentially, you can have life, and it also seems like a place where Earth life would find it a nice place to live. So why hit it?" said John Rummel, planetary protection officer for the National Aeronautics and Space Administration.
Galileo wasn't scrubbed clean of microbes before launch because NASA intended to leave it in orbit.
Years ago, however, the promise of Europa convinced NASA to err on the side of caution and plans were made to destroy Galileo.
The crash will be the first since 1999, when NASA plowed the Lunar Prospector orbiter into the moon.
Recent research has revealed the tenacity of microbial life and its ability to resist extremes of temperature and radiation. Even though Galileo has been buffeted by both, its shielded innards likely harbor viable microbes.
"We in our infinite wisdom thought nothing could survive in those harsh environments, but we are learning every day about things that can," said Claudia Alexander, Galileo's project manager.
NASA hopes to wring some scientific measurements from Galileo before its demise.