I watched the Discovery channel this morning about how Butler and Marcy discovered a planet outside our solar system. It was mentioned that Jupiter had shielded Earth from various spaceborn rocks, trapping said objects with its massive gravity, thus preventing our home planet from being bombarded to pieces. The makers of the show claimed explicitly that without Jupiter, life wouldn’t have arisen on Earth.
To me, this sounds like utter and total bullshit, pardon my French. Given Jupiter’s tiny size compared to the solar system, the fact that Jupiter’s orbit and Earth’s orbit aren’t synchronised and the fact that spaceborn rocks can in fact approach Earth from any direction, including any directions in which Jupiter does not currently reside, it seems impossible that Jupiter should capture even a slightly significant part of any potential Earth-messer-uppers out there.
Who’s the moron, me or the Discovery crew?
Jupiter protecting Earth? Utter tripe.
If it were so “protective” why does it send a protoplanet/comet smashing into the inner system every few thousand years? Look at what happened to Atlantis!
ALL THESE WORLDS ARE YOURS–EXCEPT EUROPA. ATTEMPT NO LANDINGS THERE.
Well, the Discovery channel is exaggerating, to say the least.
Whilst it is technically true that a chunk of cosmic debris could approach Earth from any direction, any inner system rock (say, with an aphelion less than Neptune’s) will almost certainly be travelling in the ecliptic, which makes the problem much less intractable. Remember, too, that gravity is an infinite-range force; it is not necessary for Jupiter to corral outlaw rock and put them in the cosmic hoosgow, merely to alter their orbits so that they do not intersect Earth’s. Jupiter is certainly capable of doing that; there is a suspiciously large number of short-period comets with aphelia around Jupiter’s orbit.
OTOH, there are a sufficient number of traces of astroblemes on Earth that we may say that Jupiter’s protection is imperfect. Net-net, it seems unlikely that Jupiter has protected Earth from a cosmic sterilant, although nobody has the required few eons of astronomical observations to answer the question with certainty.