Planetary Protection RacketAs the first planet to form in our solar system, Jupiter helped to sculpt the rest [see “The Genesis of Planets”; SciAm, May 2008]. Because of its gravity, for instance, it has regulated the rate of cosmic impacts on Earth: flinging asteroids in our direction yet also clearing many hazardous space rocks out of our way. Jupiter’s net effect depends on its mass, suggest Jonathan Horner and Barrie Jones, both at the Open University in England, in an upcoming paper in the International Journal of Astrobiology. Had Jupiter one-fifth its mass, they calculate, it would have failed to clear asteroids out--and Earth might have been struck four times more often than it has been. But if Jupiter were still smaller, it would have flung fewer asteroids toward the inner solar system to begin with--and the dinosaurs might still be walking our planet. --George Musser [More] ...
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