Ken Ham: "Stop sciencing, astrophysicists! Aliens are hellbound!"

[Anomalocaris]

Sorry to nitpick, but I think you meant Jovian rather than Jovial. Jupiter's moons are not particularly known for their cheerfulness.

Yes, but Jupiter himself certainly had a jovial glint in his eyes when he entered into cheerful conjunction with Venus and earth's moon on Dec 1, 2008. Jupiter is the left eye, Venus the right, and crescent moon the smile.

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BUt you need alot then just that. You need a large moon to skim atmosphere and slow rotation, you need a magnetosphere which means a spinning core. You also need active plate tectonics. And that is just for simple life too evolve.

I don't think the mainstream view is simple life requires any of these to evolve. Otherwise we wouldn't be looking on Mars because Mars has none of those and probably hasn't had them since around the time of the oldest evidence of life on earth.

Also, the formation of earth's moon didn't slow down the rotation of the earth, In fact it likely sped up the rotation of the earth a dramatic degree. After the moon was formed earth probably spun so fast that each day was 4 hours long and and a fixed point on earth's equator would be doing mach 10 as it wiz around with the rotation of the earth. When life first evolved earth a few hundred million years later earth was spinning slower but still very fast compare to modern rate.

Collision of the type that formed the moon was common in our system. We know 2 successful instances out of 9 planets where such collisons successed in forming a large moon around the parent planet, earth and Pluto. (Okay, give pluto a break). Impacts of similar magnitude, but didn't quite succeed in forming a moon, is thought to have happened to every terrestial planet as well. They are thought to be responsible for Mercury having a very thin rocky mantle compare to a massive iron core, Venus having retrograde rotation, and North South Dichotomy on Mars.

So we can reasonably suspect that in any planetary system with several rocky planets, those with large collison formed moons are not uncommon.