Events of June 29, 2011
(Read part 1 of Zoe's visit to the National Museum of Natural History )
Okay, so now on to what I came for in the first place — the meteorites! Touchable meteorites always get me excited, because those hunks of stone and iron are the oldest things it’s possible to touch — the ancient leftovers of the formation of our solar system. Since Earth is geologically active, old rocks are always being melted down into magma and eventually reformed as new rocks through volcanic eruptions. But out in the cold, dark vacuum of space, these rocks stayed the same for billions of years, until they fell to Earth.
(Since this is a little confusing — asteroids are large pieces of rock, dirt, and metal floating in space. Meteoroids are the smaller pieces that sometimes break off of them and also are in space. Meteors are the “shooting stars” we see as a meteoroid falls through the Earth’s atmosphere and heats up. If the meteor doesn’t burn up entirely, the pieces that reach the ground are meteorites. Hence the old joke about what a meteor that hit a plane and got stuck inside would be classified as.)
Luckily, the meteorite gallery was empty, giving me plenty of time to touch the samples with my eyes closed, breathing deeply and imagining the birth of the solar system, the chaotic early days of flying debris and cooling planets, the cold and lonely asteroids these samples might have come from, and the endless centuries of quiet waiting …
Just imagine, the one I was touching right that very moment might have come from Vesta, the asteroid I’d just seen images of earlier that day as the Dawn probe approached it …
People refer to meteorites as “space rocks”, as if they’re all the same. But just like rocks from Earth, meteorites come in different varieties. Stony meteorites look a lot like regular old pieces of stone, iron meteorites are dark clumps of metal and often lumpy. Stony-iron meteorites, the rarest, contain green and brown olivine crystals surrounded by metal and are rather beautiful.
I was also really happy that the meteorite gallery had lots of tektites! Tektites are little oddly shaped rocks found around impact craters on Earth that look like meteorites, but are actually from Earth. As you can imagine, when a really big meteorite or comet hits the Earth, the ground where it hits experiences a lot of heat — enough heat that it turns molten!
The force of the impact sends hot little rock droplets flying through the air as they cool, which often land far from the impact crater. Some become a bit like meteorites themselves — they get flung nearly into space and re-melt on their way back through the atmosphere.
Rocks from Earth that are transformed by an encounter with a space-traveling object into more beautiful and interesting forms — how’s that for a metaphor?