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Comment by Latteland | Hacker News Reader

It's fantastic to see the continuing discovery of more than "dead cold rocks" out in the solar system. I'm still feeling stunned about Pluto a year later. Ceres looks interesting (shiny sodium carbonate, and it's apparently not aliens :-)), and it still feels like an ion drive is a sci fi idea, instead it is real.

As someone with not much planetary science exposure, what is the explanation why these other smaller bodies in the solar system like Ceres seem to have more interesting variation and more carbon, possible volatiles, than the moon?

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>I'm still feeling stunned about Pluto a year later

Unless there's been some new developments, New Horizons had its Pluto flyby three years ago :)

Ha, time passes fast.

Still less than a Pluto year.

However long it's been, I can't wait for the Ultima Thule flyby.

Ceres is -73C during the daytime. Our moon is +100C during the daytime.

>> Ceres seem to have more interesting variation and more carbon, possible volatiles, than the moon?

Current theory is that the moon was the result of a collision with earth. It is similar to earth because it was once part of earth. It formed under similar conditions to earth, its differences largely do to the reduced gravity and lack of plate tectonics. Planets far away form under different conditions and are therefore more different than the moon.

>and it still feels like an ion drive is a sci fi idea, instead it is real.

It's real but it's slooooow. I mean yea, they do get much higher velocities but it takes a very long time( and thus are incapable of launching from a gravity well).

I'll guess at least some of it is that smaller bodies will have less dust blanketing the surface (just because there's less gravity to cause it to accumulate / impacts eject much more).

If I had to guess, it's because the moon was formed from a molten ball of Earth material while other moons in the solar system were formed from the same accretive processes that formed the planets.

The Earth has a lot of water which is postulated to have come from comets, I believe. The moon must have been struck by some of the same comets and didn't have a enough gravity to maybe hold onto the water and I don't think it had a magnetic field so solarwinds strip the water away but still, Ceres has water or at least organic materials, ie carbon.

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