The importance of violent asteroid collisions

[Brian G Turner]

A couple of pieces from New Scientist about the role of asteroids, and violent collisions, in the development of planetary systems and planets themselves - and perhaps, even life:

Huge space rocks could have helped start Earth’s plate tectonics

Super-Earths draw asteroids to other worlds, which may seed life

 

[Vertigo]

Interesting but it doesn't really give any reason why we ended up with tectonics but Mars and Venus didn't. After all they must have been hit by just as much space debris as the Earth.

 

[Brian G Turner]

Very true - and very good points to raise.

 

[Mirannan]

Interesting but it doesn't really give any reason why we ended up with tectonics but Mars and Venus didn't. After all they must have been hit by just as much space debris as the Earth.

Mars did, but it stalled half a billion years ago or so because Mars is smaller so it lost its heat.

Venus is a bit more interesting. AFAIK the current wisdom is that Venus usually has a largely static surface with a few volcanoes, but every so often (500 million or so years) it has a violent resurfacing of just about the entire surface. And the reason for the great difference between Venus and Earth is the presence on Earth of liquid water; the presence of large amounts of water in near-surface rocks lubricates the crust moving against the middle mantle, because rocks with water in them are less viscous. Hence active tectonics.

Venus lost its water long ago because it doesn't have a magnetic field, so solar wind protons slam into the upper atmosphere and the hydrogen in water escapes.

 

[Vertigo]

Mars did, but it stalled half a billion years ago or so because Mars is smaller so it lost its heat.

Venus is a bit more interesting. AFAIK the current wisdom is that Venus usually has a largely static surface with a few volcanoes, but every so often (500 million or so years) it has a violent resurfacing of just about the entire surface. And the reason for the great difference between Venus and Earth is the presence on Earth of liquid water; the presence of large amounts of water in near-surface rocks lubricates the crust moving against the middle mantle, because rocks with water in them are less viscous. Hence active tectonics.

Venus lost its water long ago because it doesn't have a magnetic field, so solar wind protons slam into the upper atmosphere and the hydrogen in water escapes.

Ah I hadn't realised Mars used to have tectonics and I'd forgotten about the part water plays in tectonics and Venus' lack of said water! Thanks!