#4 favourite sky-rocks

[kaberett]

(Paper crunch + resurgence of home internot has made things complicated! I am currently sat in a restaurant and putting things together.)

• Pallasites! They're very pretty, and they are (probably) what happens when you've got something meteorite-ish big enough that it starts differentiating into a metallic core (whence iron meteorites) and silicate body (hence a subset of stony meteorites) and then gets smashed up -- with pallasites being what you get from the core-mantle-boundary equivalent! So you've got the translucent yellow-green olivine (which is the major constituent of the silicate mantle and is in gem quality called epidote) embedded in iron-nickel alloy and it's pretty.
  
• The Iron Meteor I Found Under My Desk. It is about the age of the solar system, as you can tell from the scale of the Widmanstätten patterns.
  
• MARTIAN METEORS, okay. Very roughly - and I'm not looking up references for this while awesome ex-housemate C and D and K Xeno's paradox cheese-bread at Kyrgyz Kazakh House - we knew Martian meteors were from Mars before we had ever made it to Mars because, right, meteors frequently contain entrapped gases from their atmosphere-of-origin. Now the precise isotopic composition of that atmospheric gas - how much ¹H to ²H, or (more helpfully in this particular example) the ratio of ¹⁵N to ¹⁴N - lets you work out the required gravity field in order for the right amount of the lighter isotope to escape the gravity well from the top of the atmosphere. And it turns out that you calculate this out and discover that Martian meteorites must have come from a Mars-sized body, and then we sent brave space robots to Mars, and the atmospheric compositions matched (and so did the rock compositions insofar as we could tell), and basically it's all really cool.

Special bonus mention to the Moon, which is the only space rock I've actually published anything on; I continue very excited about lunar formation nonsense, and was delighted by a recent review paper on the lunar dynamo written by a friend of a friend. Lunar differentiation is a topic on which I can be very excitable with respect to Canadian analogues so!

Comments

[silveradept]

The science involving stars and planetary bodies has an impressive track record of being able to predict what will happen before being able to send experimental devices to those environments to test them. That's cool.

[kaberett]

ikr? :-) That's one of the things I kinda love about geology, too - we're working with a single experiment that's been running for like 10 billion years, over which we have zero control, and yet we manage to extrapolate usefully from our little blue-and-green marble to the rest of the solar system and the rest of the bloody universe. It's kind of magic.

[silveradept]

It is magic, yet science. Such is the nature of our abilities.

[davidgillon]

the ratio of 15N to 14N - lets you work out the required gravity field in order for the right amount of the lighter isotope to escape the gravity well from the top of the atmosphere.

{science geek}Ooh, elegant!{/science geek}

[kaberett]

Isn't it!

[fyreharper]

THAT IS SO COOL about the Martian meteors!