PASADENA, Calif. -
As obsessed with germs as the most fastidious of housekeepers, NASA plans to crash its $1.5 billion Galileo into Jupiter to avoid the possibility that the aging spacecraft could contaminate
one of the planet's moons with hitchhiking microbes from Earth.
Galileo will slip behind Jupiter at 12:49 p.m. PDT Sunday and then plunge into its vibrant and stormy atmosphere while traveling at nearly 108,000 mph.
As it hurtles downward, heat and friction will tear apart the nearly 3,000-pound Galileo, vaporizing the spacecraft and the untold millions of microbial stowaways lurking since its 1989
The crash ensures the Galileo orbiter won't smack into Europa and spill its cargo of microbes onto ice that caps the moon's enormous oceans.
The planet-sized moon is widely believed to represent 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 carried by the spacecraft, they could compromise future attempts to probe the moon for indigenous life, scientists fear.
"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," 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 never happened with Galileo,
which NASA originally intended to leave in orbit around Jupiter.
Years ago, however, the promise of Europa convinced NASA to err on the side of caution and plans were made to destroy Galileo, which now is nearly out of propellant that would allow it to
trim its course. The concern is that the gravitational tug of Jupiter could alter the orbit of the spacecraft and potentially cause it to hit Europa or another moon.
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. And satellites routinely crash to
Earth from orbit, as did NASA's Compton Gamma Ray Observatory 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.
The 14-year mission has been among NASA's most successful, despite the litany of glitches that plagued it. The focus was to have been Jupiter itself, but its stable of quirky moons and the
diversity of environments they harbor ended up stealing the spotlight.
"Galileo is a victim of its own success in a sense," said Europa expert Robert Pappalardo of the University of Colorado at Boulder.