[jennyp]

If Jupiter were even bigger, superjovian, 4 times to 10 times more massive, it wouldn't allow even earth to exist, it would sweep that up, too.

Ah, assuming it was in the same orbit as Real Jupiter, right? If its orbit was farther away, we could get by with a bigger Jupiter than that, right?

[Crusher138]

Isn't our moon a big meteor sweeper also? Seems that the solar system acts like a big double filter. Jupiter takes what it can and the moon catches most of the rest. We still get some hits, but far fewer than we would otherwise.

I think I remember a science fiction story about a civilization that exists on a planet that has regular cataclysmic events that set back progress. They advance, eventually, but by the time they arrive at the Gallactic Intelligence Party, everyone has already left and moved on. If I remember the story correctly, they left some pretty neat stuff behind. I can't for the life of me remember the name of the story or the author. Oh well.

[RightWhale]

If its orbit was farther away, we could get by with a bigger Jupiter than that

Most extrasolar planets discovered so far are larger than Jupiter, superjovian. Most are very near their primary compared to Jupiter's position. In comparison, the solar system is an oddity, not like other star systems we know about.

But in 2006 NASA will launch the Kepler telescope which will scan the stars for earth sized planets. Our state of knowledge of actual planetary systems will improve.

Here are a couple of articles, both fairly current on Kepler and observed planetary systems.

Strange Object Found, Defying Ideas of Solar System Formation

Kepler Mission to Find Earth-Like Planets Gets Green Light