Of Meteorites and Men

What I lack in looks in make up for in sarcasm. And yes, I do wear bowties frequently.

Yes, I do wear bowties frequently.

Hello Paleoposse! My name is Ryan Brown and I’m one of the newest victims bloggers here at the Paleocave. I made an appearance on Episode 134 where I talked a bit about meteorites and the asteroid mining company, Planetary Resources. I blog over at Glacial Till where, confusingly enough, I do not actually talk about glaciers. Most of my blogging centers around meteorites, planetary science, and some geology. I have no plans on abandoning my own blog, so keep your eyes open for cross-posts between the two sites.

A little about myself: I’m an undergrad in my senior year at Portland State University where I’m majoring in Earth Science with a minor in Space and Planetary Science. While keeping up with my normal classes, I can also be found doing independent research at the Cascadia Meteorite Lab on campus. I’ve been there since I was a freshman learning about the wild world of meteorites and it’s finally culminating in two co-authored papers (one that’s in peer review and the other being written) and a rather unhealthy addiction to space rocks and caffeine. And somewhere in all that, I’ve managed to squeeze in time to lead the skeptic group on campus.

So, why meteorites? What makes this relatively niche science so fascinating? In short, meteorites are the left over building blocks of the solar system. They are to meteoriticists (a person that studies meteorites) what fossils are to paleontologists. They allow us to understand how planets formed and evolved out of the great chemical cloud that swirled around the young protosun 4.5 billion years ago.

We group meteorites into three main categories:

  1. Stony meteorites 
  2. Stony-Iron meteorites
  3. Iron meteorites

These three categories can further be broken down into smaller groups based on shared characteristics in mineralogy and chemistry. But we’re gonna keep it tidy and just stick with the three main groups.

Stony Meteorites

The stony’s come in two different flavors:

  • Ordinary chondrites- They’re called ordinary because they account for nearly 85% of known meteorites. In my humble opinion, a better name would be common instead of ordinary.
Ordinary chondrite NWA 869 (Image from Wikipedia)

Ordinary chondrite NWA 869 (Image from Wikipedia)

 

  • Carbonaceous chondrites- These meteorites are considered the most primitive in terms of chemical evolution. They’ve seen very little to no heating, and as a result, contain water in the form of hydrated minerals. Cooler yet, the chemical make-up of these meteorites closely approximates that of the sun. This means we can study them to learn about the very early days of the solar nebula before the planet making process took-off.
One of the more famous carbonaceous chondrites- Allende (Image from Wikipedia)

One of the more famous carbonaceous chondrites- Allende (Image from Wikipedia)

 

  • Some achondrites- These are meteorites without chondrules, or these spherical silicate inclusions. I say some because not all achondrites are stony. Some fall under the stony-iron category and, if you’re feeling particularly heretical, the iron category. Those that are stony come from either the moon, Mars, or asteroids such as Vesta 4.
The newest martian meteorite, NWA 7034. We'll cover this one in detail in the next post. (Image from NASA)

The newest martian meteorite, NWA 7034. We’ll cover this one in detail in the next post. (Image from NASA)

 

Stony-Iron Meteorites

These are meteorites that are made up of significant portions of metal and rock. In some cases, you can get a near 50/50 compostion. Some of the most striking, and priciest, meteorites come from this category.

The Esquel pallasite. The presence of olivine grains in a metal matrix is thought to represent mixing of the mantle with the core from a catastrophic impact. (Image from Wikipedia)

The Esquel pallasite. The presence of olivine grains in a metal body is thought to represent mixing of the mantle with the core from a catastrophic impact. (Image from Wikipedia)

 

Iron Meteorites

And then there are the iron meteorites. These are thought to be from the cores of planetismals that grew large enough to develop an iron-nickel core, but suffered some sort of impact that disrupted the parent body. Famously known for the cross-hatched, Widmanstatten pattern.

The iron meteorite, Seymchan, displaying the Widmanstatten pattern. (Image from Wikipedia)

The iron meteorite, Seymchan, displaying the Widmanstatten pattern. (Image from Wikipedia)

 

What I’ve written here isn’t comprehensive in the slightest and it’s not meant to be. This is just to give you an idea of the complexity of the stuff that falls from space. I’ve already written a lot on my own blog under the Meteorite Monday series that covers these beauties in greater depth. If you’re interested in learning more, click on the link provided and peruse my stuff. Or post your questions in the comment section below and I will do my best to answer them.

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