Interesting Reasoning...

NASA figures that it's best to crash Galileo, the probe that's been hunting around near Jupiter for eight years. It's lived six longer than anyone expected it to, the faithful little probe that sends photos and data back here, at increasing intervals. Eight years on a space mission is enough; besides, it won't be long that Galileo's fuel will be so low, that NASA won't be able to control it, anyway.

Jupiter's moon Europa, where astronomers believe moisture lurks, might be endangered, if the probe were to crash there, and, without control, impact on that moon might happen. Some day, NASA figures, we'll want to explore it; and we won't want to find any terrestrial microbes there. NASA is going to crash Galileo into Jupiter, rather than try to land it (a long shot, at best), because, they say, Earth germs that might have survived a decade and a half of space flight would be destroyed in the crash, but might survive a 'landing,' possibly contaminating the moon forever.

In 1995, Galileo dropped a parachute probe into Jupiter's atmosphere. That probe may have been sterile; or the concern simply wasn't a concern at the time. Now it's Galileo's turn. Rather than leave the probe just flying around Jupiter until it eventually falls out of orbit and burns up in the planet's atmosphere, NASA's going to crash it into the planet, ensuring its total destruction.

Ordinarily, NASA explained, they decontaminate their spacecraft, to avoid that sort of problem for other worlds; but Galileo, launched in 1989 from Atlantis (it was supposed to have gone up with Challenger, which became tragically unavailable), didn't get the pre-launch 'scrubbing.' Followup probes and missions won't pollute.

There's another thing: NASA doesn't want the inhabitants of Jupiter to know we're there. (Galileo's already been around the planet 34 times.) Any traces of a spacecraft might tip them off...

FMI: www.spaceflight.nasa.gov