Tuesday, December 10, 2019

Panspermia followup

A few years back I mused a bit about life from Earth seeding other planets. You'd need speeds of order 27km/sec to get to Mars, because it is uphill from the Sun. That's pretty fast, and unless a chunk was entrained in a lot of other stuff going the same way, the heating you get from compressing the atmosphere on the way out would tend to melt it. But maybe...

I thought I should follow up on that. O'Keefe and Ahrens modeled impacts on Mars and the Moon, and write that "In addition, we have calculated the internal energy of ejecta versus ejecta velocity. The internal energy of fragments having velocities exceeding the escape velocity of the moon (∼2.4 km/sec) will exceed the energy required for incipient melting for solid silicates and thus, the fragments ejected from Mars and the Earth would be melted."

This is already at quite a bit lower energy than that required to ship chunks away from the Earth.

You might get some extra (not quite so shock-y) speedup from turbulent interactions in the debris cloud, but I don't think you can get another order of magnitude.

Poor fried spores--not much chance for a new home.

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