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The Michigan Meteor and possible meteorites January 17, 2018

Posted by aquillam in Astronomy, MichiganAstro.
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Last night a rather large meteor exploded over Michigan. Stories and video are all over social media. The American Meteor Society website was down for a while, but it’s back up now, and they have a map where you can see where everyone who saw it was, and the probable ground path.
This was a bolide, a very bright meteor that explodes or breaks up, and usually makes it into the lower atmosphere. That makes it more likely that fragments may have made it to the ground.  So if you happen to live or own property near the ground path, you might want to go look for some fragments.
Some things to know:
If you suspect you might have an impact site, TAKE PICTURES BEFORE YOU TOUCH ANYTHING. Then, put something down for scale, like a quarter, or a rock hammer, and take a few more pictures. Then and only then, should you pick up and examine the rocks.
The glow of the meteor is mostly from the air around it. That will make the surface hot, but, like fried ice cream or baked Alaska, the inside will still be the icy cold of outer space. If you find a molten ball of goo, or something that looks like it was recently a molten ball of goo, it’s not a meteorite. This is slag, not a meteorite.


This is slag, not a meteorite. http://meteorites.wustl.edu/id/slagq_gil.jpg

If it’s a fragment of last night’s meteor, it won’t have weathered yet, so it should have a thin fusion crust, which should be dark.


This cross section shows the crust is fairly thin. It is also relatively smooth, but with a crackle-finish like texture. http://www.meteorite-recon.com/home/meteorite-documentaries/meteorite-fusion-crust

It came in at an angle, and probably broke into smaller pieces. Small pieces make small craters, but the snow here is rather fluffy. If small meteorites hit deeper snow, they may actually melt holes through it, and you’ll find the meteor stuck to the bottom of an ice core. In shallow snow over solid ground, you’re probably looking for fairly small dark rocks in shallow oblong craters maybe up to 10 times wider than the rock. The crater size varies dramatically though.
Very large meteorites can be valuable. Meteorites from events that were documented and witnessed (like this one) can be valuable. But don’t expect to buy a car by selling a couple small meteorites on eBay. Maybe a nice dinner at a fancy restaurant for your family. If you think you have a meteorite and are considering donating or loaning it to science, I’d suggest starting with NASA’s “Watch the Skies” site.