Gas giants as vacuum cleaners

[Cormoran]

Yep, its me again

With all these terribly knowledgeable people about, I was wondering what the consensus is on the theory that life would not have evolved very far on Earth without Jupiter (and possibly other Gas Giants) acting as gravitational sinks for cometary masses?

It seems to make a deal of sense to me.

I ask because I'm developing code on a solar system generator, designed to output to .ssc files (with additinal data), and one thing I want to get right is texture assignment and characteristics of 'Earth-like' planets in systems without a large Gas Giant.

Let me know what you think, folks.

Cormoran

[ajtribick]

Ian Stewart and Jack Cohen were not very impressed with this idea in Evolving the Alien, mainly because they point out that while Jupiter throws comets out of the system, it also throws asteroids in.

Then again comets have more momentum than asteroids would do because they have further to fall, so to speak. So a comet impact could be more devastating than an asteroid impact.

So I suppose this would depend on if the gas giant in question has created an asteroid belt by disrupting the accretion of a nearby planet.

However this is all second-hand knowledge so I'm sure someone a lot more knowledgeable than me will come in and contradict this.

[Cormoran]

Ian Stewart and Jack Cohen were not very impressed with this idea in Evolving the Alien, mainly because they point out that while Jupiter throws comets out of the system, it also throws asteroids in.

How embarrassing I own a copy of that book! It's under a pile of GURPS stuff by my bed ....

I must dig it out

Any other opinions?

Cormoran

[Evil Dr Ganymede]

I think the Earth's large Moon also played a good part in being a target for (or at least deflecting) asteroids etc that would have otherwise hit Earth.

[Cormoran]

Another good point, Dr. G., but conversely, again, the Moon would gravitationally affect objects that might otherwise not hit the Earth.

Additionally, would not the combined mass of the Earth/Moon system be more 'attractive' to passing junk of one form or another?

I don't know about all this. Its almost as if some scientists are trying to think of reasons for life, and earthlike worlds, to be less common. I know in some cases its an attempt to explain the Fermi Paradox, but in some cases, such as the need for a Jovian matter-sink, its a case of they 'doth protest, TOO much'.

Anthropic principles, anyone?

On a similar subject, some opinions suggest that the recent discovery of so many epistellar giants indicates that Solar Systems like ours may be uncommon. It occurs to me that, because the effect on a stars motion from a close giant world is far greater than that from more 'ordered' systems, epistellar giants are just easier to find.

I'm torn between three positions.

The first is a purely rational analysis of available data, combined with the principle of mediocrity. By that token, Earthlike worlds are probably rather rare. Occam's razor....

The second position is from the standpoint of being a writer and Gamemaster, which makes me feel that for dramatic purposes, Earthlike worlds and life should be quite common (Maybe 1 in 50 systems). Niven's PenKnife...

The third is simply my hope that life is EVERYWHERE.... In the oceans of Europa....in the frozen aquifers of Mars...in the atmosphere of Gas Giants....in the hearts of comets and the depths of molecular clouds. Cormoran's blunt instrument...

Oh good grief...its late and I'm waxing lyrical... sorry