Meteorite Monday: Sikhote-Alin Meteorite

Here’s a really cool documentary about the Sikhote-Alin iron meteorite that fell in Russia in 1947. It was made by the Russian government, but has English subtitles. The film is about 10 minutes long and is actually the first part of an 18 minute documentary. Meteorites Australia posted this video to YouTube and has the full length documentary on their website.

What I find really amazing is that Russian scientists were able to determine where the meteorite came from based on it’s trajectory and the speed at which it entered the earth’s atmosphere. 70 tons of meteorite crashed its way to the earth and is one of the more common pieces found in collections. That doesn’t make it any less spectacular though- after all, it is the core of a small planet that didn’t survive the early formative years of the solar system.

 

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Meteorite Monday: Iron Meteorites

Iron meteorites are, in my opinion, some of the coolest and most interesting specimens available for study. They have the distinction of being one of the more rare observed meteorite falls (roughly 5%), but, mass wise, being the most common (1). In fact the largest meteorite ever recovered in North America was the iron Willamette Meteorite. As the name suggests, it was found here in 1902 in the Willamette Valley in the town of West Linn. This monster weighs in at 15.5 tons and can now be found in the American Museum of Natural History.

The important thing to keep in mind is that iron meteorites are not chondrites. They are about as different as sandstone and basalt. Both may be rocks, but they’re petrologically unique. To continue with the comparison, chondrites are the result of accreted space dust and debris- ok, it’s actually more complicated than that, but for the purpose of this post, it’ll do. And just as basalt forms from magma that comes from the mantle of the earth, so to do iron meteorites come from the mantle of planetesimals. So, if you have the chance to see and handle an iron meteorite, you are actually interacting with a fragment of a failed planet’s core. Pretty cool, eh?

It becomes even more interesting when you see an iron meteorite with the lovely Widmanstatten pattern etched across its surface. This lattice like network is the result of mixing between its two primary iron-nickel minerals, kamacite and taenite, while molten in the core of the planetesimal. Taenite is the nickel rich (about 25%) mineral component of iron meteorites and is highly acid resistant. This is important because acid etching is used on the cut surface of an iron meteorite in order to expose the Widmanstatten pattern. Too much taenite and the structure doesn’t develop (2).

Gibeon Iron Meteorite with Widmanstatten pattern. Image from New England Meteoritical Services.

There is a lot more that can be said in regards to iron meteorites, but I’m going to end it here. I want to save the rest for future posts where I can get into more detail.

1. Hutchison, Robert. Meteorites: A petrologic, chemical and isotopic synthesis. Cambridge University Press. 2004. P. 322.

2. Benedix, Gretchen., Russell, Sara., Smith, Caroline. Meteorites. Firefly Books. 2009. P. 64-65.