Hugh Pickens writes "Last Sunday, an object, probably a comet that nobody saw coming, plowed into Jupiter's colorful cloud tops, splashing up debris and leaving a black eye the size of the Pacific Ocean — the second time in 15 years that this had happened, after Comet Shoemaker-Levy 9 fell apart and its pieces crashed into Jupiter in 1994, leaving Earth-size marks that persisted up to a year. 'Better Jupiter than Earth,' say astronomers who think that part of what makes Earth such a nice place to live is that Jupiter acts as a gravitational shield, deflecting incoming space junk away from the inner solar system where it could do to humans what an asteroid apparently did for the dinosaurs 65 million years ago. 'If anything like that had hit the Earth it would have been curtains for us, so we can feel very happy that Jupiter is doing its vacuum-cleaner job and hoovering up all these large pieces before they come for us,' says Australian amateur astronomer Anthony Wesley, who first noticed the mark on Jupiter. But others say the warm and fuzzy image of the King of Planets as father-protector may not be entirely accurate. In 1770, Comet Lexell whizzed by the earth, missing us by a cosmic whisker after passing close to Jupiter. The comet made two passes around the Sun and in 1779 again passed very close to Jupiter, which then threw it back out of the solar system."