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Meteors, Meteorites,and Asteroids, oh my!

Fri, 12 Apr 2013 03:52:25 CDT
By: Jim Browne

Meteors, Meteorites,and  Asteroids, oh my! Spring is here, birds are singing, but the world could end in a heartbeat. GLT's Jim Browne talks with an ISU professor about how various heavenly bodies could spell doom for our planet:

Comets, asteroids, meteors, they've been in the news a lot this year.

(sx) various anchors nat news ...atomic bomb

    So, is the world going to end?:

   "(laugh)... I think a lot of people would ask that question."

     That's Illinois State University researcher Tasha Dunn. She and her students study meteors, asteroids, meteorites, shooting stars, all those things that fall out of the sky, or zip past us a phenomenal speeds. So, are we whizzing past all of this stuff, or is it whizzing past us?

     "Well, technically we're both whizzing past each other, because those asteroids, just like Earth, are circling around the Sun. The ones that are concern to us are called Near Earth Objects, and so those are the ones that have orbits that cross the orbit of Earth, and so they are kind of in the way, so if they happen to come close enough to the Earth, there's the potential that the two objects will collide as they're both rotating around the Sun." (I used to have a figure eight road race set) "Exactly, it's very similar to that so there's going to be a specific point on that road race board, or in the orbits of the planets, where those two objects could potentially collide."

     What makes a meteor a meteor, and an asteroid an asteroid?

     "Meteors and asteroids are both basically the same thing. When an asteroid comes into the Earth's atmosphere and scrapes the atmosphere, THAT'S when you call it a meteor, but it's still an asteroid. But before it can be called a meteor, it has to come within the Earth's atmosphere."

     And then it lands....

     "And then it lands, if it lands that's when you call it a meteorite. But an asteroid, a meteor, and a meteorite are all the same thing, it's just location, location, location."

     The hunks that they're talking about, the asteroids that have been whizzing past us of late, 13,000 tons, 17,000 tons, they're talking about, how dense are asteroids?

"It depends. The one that landed in Russia had a density of probably about 3.2 grams per cubic centimeter, which is very similar to a rock you would find on Earth.   Now, some asteroids are a little bit less dense because they've broken apart, and re-created back together and so they're made of a lot of air. But the typical density of an asteroid is about like a rock on Earth."


     "Like a granite, yeah, exactly."

     It's hard to believe a rock that size having global impact

     "Well the speed is the primary thing. Because we get hit by pieces of asteroids, by meteors a lot, honestly when it comes down to it.   Most of the time we just don't notice, because they're so small, and often objects when they meet with the atmosphere will be broken apart. Completely, because they're so small to begin with. But, it it's coming in with a hyper velocity speed, and it's very very large, if you've got speed and size, then the impact from that event is going to be a catastrophic impact.

Mass and speed, energy.

"Yes, exactly."

     Geologists like you look at a meteorite, like those discovered about 12 years ago in the antarctic and say 'Ah! this meteorite came from Mars!' and I know that. How does a geologist 'know' that?

     "Well, with Mars specifically there are three things that we look for. And the first is what we call the 'crystallization age,' and that means the age that that rock crystallized from a magna. Now, first off let me say there are very few places in the solar system where you can crystallize a rock from magma, because most of the planets are not active. Mercury, the moon, those are not active planetary bodies. The only places in addition to Earth where you can make a volcanic rock is Mars and Venus. And so, because the crystallization are young, like 1.8 Million years, then that means that they had to come from a planetary body that was vulcaniclly active 1.8 Million years ago, and so that would rule that down to Mars and Venus. The, if we look specifically at the compositions, what these meteorites are made of, the nitrogen in particular, in those particular meteorites is exactly the same as the atmosphere on Mars. And the minerals, the olivine and the peregrine have exactly the same magnesium and iron compositions as the Martian rocks"

     Where do you get your meteor samples?

     "These samples have actually been a little bit more difficult for me to get than typical. Most often what I do is request samples from the Smithsonian Institute for example. I also get a lot of stuff from the Natural History Museum in London. These samples though, because there are so few of them, they don't have any at the Smithsonian or the Natural History Museum. And so I've had to go everywhere, and talk to people in Russia, and other places in the United States, and I've actually ended up buying several of them myself because they aren't available for loan from academic institutions. So far I've bought four and I've got several that are going to be coming from France and other places."

Is there an asteroid black market?

     "There is kind of a meteorite black market yeah. Sometimes people will sneak into the desserts of Dufar and bring back meteorites, and so we have a lot of meteorites from Dufar and people are sometimes hesitant to study them because they haven't really gone through the system in the way that a lot of other meteorites have."

   Doctor Tasha Dunn studies a type of meteor known as Chondrites, early primal collections of matter, that have never melted, and contain the ingredients from the solar nebula some 4.5 Billion years ago. Dunn's work just earned her a $125,000 grant from NASA.     

     Tasha Dunn says it'd be hilarious to find a meteor near the ISU campus:


Dunn says if it comes down to searching for meteorites at the south pole, and being shot into space to examine an asteriod, she's already made up her mind:


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