Pasadena, Calif. ? NASA plans to crash its $1.5 billion Galileo spacecraft into Jupiter next 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 1:49 p.m. CDT Sunday, the aging probe will plunge into the planet’s stormy atmosphere at a speed of nearly 108,000 mph.

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 spacecraft 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, perhaps in pools of water warmed by radioactive plutonium the spacecraft uses to generate electricity, 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.

NASA typically scrubs its spacecraft clean of microbes to prevent what it calls the “forward contamination” of other places in the solar system. That wasn’t done with Galileo, which NASA originally intended to leave in orbit around Jupiter.

The crash will be the first since 1999, when NASA plowed the Lunar Prospector orbiter into the moon. In 1994, NASA crashed the Magellan orbiter into Venus. Satellites routinely crash to Earth, as NASA’s Compton Gamma Ray Observatory did in 2000.

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 seventh and likely last project manager at NASA’s Jet Propulsion Laboratory in Pasadena.

The 14-year mission has been among NASA’s most successful, despite a litany of glitches. Its focus was to have been Jupiter itself, but the planet’s quirky, diverse moons — including Io, the solar system’s most volcanically active body — stole the spotlight.

NASA hopes to wring some scientific measurements from Galileo before its demise. When the end does come, 1,500 people associated with the mission are expected to gather at the lab to mark the occasion.

“It will have some of the flavor of a wake,” Alexander said.