From Mars to Earth??
April 4, 2011 3:03 PM   Subscribe

I was listening to this Fresh Air interview today and wondered how they know a meteorite is from Mars.

Apparently scientists can tell that certain meteorites came from Mars (or the moon) but 1) how can they tell that and, 2) how did it get to Earth?
Thank you.
posted by Rad_Boy to Science & Nature (8 answers total) 1 user marked this as a favorite
 
Rocks from Mars get to Earth by being blasted off Mars from impacts with foreign bodies and then getting sucked into the Earth by Earth's gravitational pull.
posted by dfriedman at 3:05 PM on April 4, 2011


They can tell based on what they are composed of. Mars has a high amount of X in its earth...jupiter is a big ball of gas, etc.
posted by hal_c_on at 3:17 PM on April 4, 2011




I'll let Ms. zamboni, PhD candidate in Mars geology, handle this one.

Quick answer: For martian meteorites, the radiometric ages are much younger than those of the meteorites we have (up to a couple of hundred million years, as opposed to ~4.5 billion years), and the gas trapped in bubbles within some of the meteorites is an exact match for the martian atmosphere as measured by the Viking landers. For lunar meteorites, I believe it's that the mineralogy and isotopic abundances match those from the Apollo (American) and Luna (Soviet) samples brought back from the Moon.

When an impact is energetic enough, the ejecta can end up going faster than the host body's escape velocity (i.e., it's kicked off the Moon or Mars). In such an event, part of the outer surface of the ejecta rock melts. If the host body has an atmosphere (i.e., Mars but not the Moon), by the time the melt solidifies, it can contain bubbles of the ambient atmosphere.

Most of the martian meteorites we have, and we have about 40 or so, spent about 1-20 million years in space. We estimate this based on cosmic ray exposure age dating -- certain isotopes form as a result of cosmic rays hitting the meteoroid while it's in space.

posted by zamboni at 4:37 PM on April 4, 2011 [3 favorites]


Remote sensing data from different captured wavelengths coupled with mass spectrometers on the various Mars Rovers give hints to things like isotope ratios, mineral presence, rates of elemental decay, and specific geologic features known about different astronomical bodies.

Also, you should realize that just about everything that makes it through our atmosphere is from either A) the asteroid belt, B) Mars, or C) the Moon.
posted by JesseBikman at 5:05 PM on April 4, 2011 [1 favorite]


Sorry, I meant to say clues from things instead of hints to things.
posted by JesseBikman at 5:06 PM on April 4, 2011


Wrote my dad (ANSMET meteorite hunter/all-around meteorite scientist nerd/total dork) and asked if he had anything he'd like to add:
Looks like Ms Zamboni (cool name) got it right, i.e., age and trapped gases. One more piece of evidence is that examining Martian meteorite mineralogy would lead you to a planet about the size of Mars (mineral assemblages, crystallization rates, etc.). In fact people believed that for many years but A) didn’t have trapped gas analyses, and B) didn’t believe that you could physically blast it off the surface into an earth crossing orbit without turning it completely into glass. Once it was shown that it could be done, then the community climbed on board. Interesting story there too involving the physics of large impacts on planets with atmospheres…
posted by fiercecupcake at 6:47 AM on April 5, 2011


Remote sensing data from different captured wavelengths coupled with mass spectrometers on the various Mars Rovers give hints to things like isotope ratios, mineral presence, rates of elemental decay, and specific geologic features known about different astronomical bodies.

Ms. zamboni would love it if there were mass spectrometers on current Mars Rovers, but it just ain't so. Spirit and Opportunity are capable of detecting certain minerals with their infrared and Moessbauer spectrometers, but they cannot detect isotope ratios nor rates of elemental decay. You might be thinking of Mars Science Lab, the next rover, due to launch in November.
posted by zamboni at 8:58 PM on April 5, 2011 [1 favorite]


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