Friday, May 24, 2019


The Astronomy Picture of the Day of Bennu is very curious. It looks like a scree field, and it probably is scree all the way down. But the rocks are interesting. Much of the stuff lying around is clearly pitted and "space-weathered" and looks like concretions of smaller bits of stuff--the sort of thing you might expect from gentle gravity pulling dust and stuff together. But some show clean cleavage, as though a hard rock was cracked. If asteroids were built of accumulated cruft, like comets are supposed to be, all of it should be rough-looking.

Meteorites tell us that there are some hard bits in the asteroids--indeed some theories hold that a planetoid, big enough to have the heat and pressure to make rocks, broke up to make the asteroid belt--and all that frail-looking stuff suggests that a lot of the meteor gets splattered away high up in the atmosphere.

The meteor trail in the air is mostly glow from heated oxygen and nitrogen, but I'd expect some amount of light from the frying meteor as well. If (That's a big if. As it says at the link, usually you don't have a spectrometer pointed at the meteor trail.) you could compare the spectrum at the start and at the end, and subtract off the atmospheric contribution, you might be able to tell the difference between the composition of the soft cruft and the harder bits.

1 comment:

Assistant Village Idiot said...

Looks like a tough scramble to the top, but if 500 meters is the max, I think I could manage it.

A bit nippy, I'll bet.