25 September 2008

Rocks in from space: Accretionary Wedge #13

Posted by Jessica Ball

Unfortunately, my experience with extraterrestrial geology is limited – I haven’t taken a planetary geo course yet, although there’s a planetary volcanology expert not twenty yards away, and I intend to take advantage of that next semester. So I’m going to take a little nostalgia trip and talk about one of my favorite places in the world, the Smithsonian Institution’s National Museum of Natural History. (Don’t worry, this will connect to the space theme eventually!)

When I was very young, I used to visit the museum all the time. It wasn’t unusual for me to insist on going to visit more than once a month, and sometimes during the summer I’d spend even more time there. (My father worked in DC, and was usually the one to escort me.) I remember that the old Gems & Minerals exhibit, while cool to me because I was crazy about that sort of thing, was not exactly the most exciting place in the world. A lot of the displays looked like this:

(This is actually from the NMNH’s Research Training Program tour of “behind the scenes”, but it’s approximately the same as the old exhibit.)

Pretty traditional stuff. But then, for a couple of years, the exhibit underwent a major renovation. And when it reopened in 1997, it looked like this:

The new exhibit so completely exceeded the old one in awesomeness that I still grin like a little kid whenever I walk in there. And the first thing you see? (Or, in my case, the second thing after I’ve rushed to the volcano/earthquake section to jump around next to the seismograph…) Space rocks! (I actually don’t have any of my own photos of the meteorites – I’m always way too busy reading things to take pictures, and besides, it’s not like I can’t go back.)

Anyway, spending so much time at the museum – around the meteorites, among other things – was one of the reasons I became a geologist. And when I was in high school, I was so annoyed that I couldn’t take geology classes yet that I spent two summers as a volunteer for the Global Volcanism Program at NMNH. It was mostly helping edit the Bulletin of the Global Volcanism Network, which was fun, but the volunteers also got some perks – among them, behind-the-scenes tours of all the neat stuff that the public doesn’t get to see. And one of those tours was in the National Meteorite Collection.

It’s hard to describe how amazing it is to stand in a room holding a rock and knowing that it’s totally alien, had little to do with the Earth until it impacted, and that it could have come from millions of miles away. And hey, if the rock just happens to be this one…

Well, let’s just say that I considered holding this rock (or, at least, its spiffy “don’t touch” bubble) one of the highlights of my geologic career. In case you don’t recognize it, this is ALH 84001, the little Mars rock that caused such a stir a few years back when someone thought they saw critters in it. The Smithsonian keeps it under lock and key in its own secret-agent-style locked metal suitcase, and brings it out for visiting dignitaries (and rock-crazy highschoolers, apparently). Here’s a close-up:

(From here.)

I also had the opportunity to hold a piece of a pallasite (a stony-iron meteorite with lots of olivine) like this one:

And, as a special treat, the curator thought it would be fun to hand me the core of a nickel-iron meteorite. Those meteorites have densities of between 7 and 8 g/cm3, and the cores have even higher densities, which means that something the size of a football weighs a hell of a lot more than a football (or even a normal rock the size of a football). Let’s just say that I barely managed not to drop the thing and crush all my toes.

So, there you have it. My intense fascination with the Smithsonian’s collections led to a summer volunteer position which led to my first intimate contact with rocks from space, which in turn stoked the fires of geological ambition even higher. That tour was one of the neatest things I’ve every had the opportunity to do, and I highly recommend exploiting any Smithsonian contacts to get yourself in there the next time you have a chance to visit Washington DC.