The Moon

The Moon is crucial for a number of reasons.

Initial Earth/Moon Impact and Continental Drift

Some more random thought that may not be true....

The strongest theory for the formation of the Moon says that a Mars-sized asteroid impacted the early Earth about 5 billion years, back when the whole solar system was still taking shape. This impact ripped of a lot of the Earth's material, throwing it into space. Some fell back to the earth, some escaped Earth's gravity, and the rest formed the Moon, and supposedly an orbit much closer to the Earth than today. (I heard 200,000 miles closer than now.)

Well, when the asteroid impacted the early Earth, I think the crust and a lot of mantle material mostly from one side of the planet. That left an imbalance. The side without the crust cooled faster and sank. While the crust insulated the other side, in fact heat built up. This sinking on side started pulling apart the other side, and continental drift began. (See the Earth page and continental drift, the geologic carbon cycle, and stable climate for reasons on why continental drift is important.)

Mars and Venus don't have moons formed in this fashion. Mars cooled evenly on all side, so has no continental drive. Venus has a even crustal cap on the whole planet. (Some experts say it's a thick crust; while others says it's thin. The data is ambiguous on this point. Both sides agree it's uniform.) IIRC, the crust is also relatively young. I'm not sure how many data points we have, or how representative of the planet in general they are, but I'm going to make a leap here and follow some expert's-whose-name-I-forgot conclusion and think the planet experienced a massive, geologically rapid, planet-wide crustal overturn. That also suggests no continental drift.

Tidal Pools and Tidal Zone

We all know the Moon creates our tides. But why are tides important?

Some have said the life began in tidal pools, or along shore affected by tides. One reason for thinking this occurred in tidal pools is that the resources starting life were too dispersed in the environment in general. However, in tidal pools, the material is washed in on the waves during high tide, then the water dries up some during low tide, concentrating the material. Then more material delivered during the next high tide, and so on, concentrating the material thick enough to start life. I'm told the days were only 6 hours long back them. That's means a new high time every 3 hours. With the Moon so much closer, its gravity would have produced higher tides. I'm guessing that pools at the high tide zone didn't fully dry out before the next high tide and its waves refilled it.

The tidal zone seems like the best place for life to begin growing. After all, that is where the stromatolite grow even today.

Last-Chance Meteor Vacuum

It's said the moon also acts as a last shield against meteor impacts. The Moon's gravity can deflect incoming meteors enough to miss us, but it seems to me that it would also deflect those that would miss us enough to hit us. Perhaps it's in the percentages, more deflects that miss than hits. Anyway, any meteors that strike the Moon definitely miss the Earth, and you can see that happened a lot in the past, not so much in recent history. Perhaps that was a key role when life was finding it's foothold? However, IIRC, there was an impact on the Moon about 600 or so years ago. Jupiter plays a bigger role in this respect.