Moon and Jupiter

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The Moon and the planet Jupiter put on a nice show the next couple of evenings. Jupiter looks like a brilliant star to the upper left of the Moon as darkness falls tonight.

Jupiter has a big entourage of moons of its own -- more than 60, and still counting. Most are small and insignificant. But a few are interesting worlds in their own right.

Perhaps the best example is Europa. It's about as big as our own Moon. But while the Moon is almost completely dry, the surface of Europa is coated with ice, which may float atop an ocean of liquid water.

The ocean may be warmed by heat from Europa's interior. Water and energy are two key ingredients for life, so it's possible that living organisms might inhabit Europa.

Nobody wants to take a chance that microbes from Earth might contaminate Europa. So when the Galileo spacecraft neared the end of its mission a few years ago, scientists decided to crash it into Jupiter instead of running the risk that it might someday hit Europa. Galileo had spent years orbiting Jupiter, where it was zapped by deadly radiation. Even so, there was a remote chance that some Earthly "bug" might have survived inside the craft. And no one wanted to run the risk that such a bug could survive on Europa -- and perhaps even flourish.

Again, look for the Moon keeping company with Jupiter the next couple of evenings. Brighter Venus is well to their lower right. More about the Moon and Jupiter tomorrow.

Script by Damond Benningfield, Copyright 2008

For more skywatching tips, astronomy news, and much more, read StarDate magazine.