Mars Rover Finds Rock Resembling Meteorites That Fell to Earth

MEDIA RELATIONS OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011 http://www.jpl.nasa.gov
Guy Webster (818) 354-5011 Jet Propulsion Laboratory, Pasadena, Calif.
Donald Savage (202) 358-1547 NASA Headquarters, Washington, D.C.
NEWS RELEASE: 2004-104 April 15, 2004
Mars Rover Finds Rock Resembling Meteorites That Fell to Earth
NASA's Opportunity rover has examined an odd volcanic rock on the plains of Mars' Meridiani Planum region with a composition unlike anything seen on Mars before, but scientists have found similarities to meteorites that fell to Earth.
"We think we have a rock similar to something found on Earth," said Dr. Benton Clark of Lockheed Martin Space Systems, Denver, science-team member for the Opportunity and Spirit rovers on Mars. The similarity seen in data from Opportunity's alpha particle X-ray spectrometer "gives us a way of understanding 'Bounce Rock' better," he said. Bounce Rock is the name given to the odd, football-sized rock because Opportunity struck it while bouncing to a stop inside protective airbags on landing day.
The resemblance helps resolve a paradox about the meteorites, too. Bubbles of gas trapped in them match the recipe of martian atmosphere so closely that scientists have been confident for years that these rocks originated from Mars. But examination of rocks on Mars with orbiters and surface missions had never found anything like them, until now.
"There is a striking similarity in spectra," said Christian Schroeder, a rover science-team collaborator from the University of Mainz, Germany, which supplied both Mars rovers' Moessbauer spectrometer instruments for identifying iron-bearing minerals.
Mars Exploration Rover scientists described two such meteorites in particular during a Mars Exploration Rover news conference at NASA's Jet Propulsion Laboratory, Pasadena, Calif. One rock, named Shergotty, was found in India in 1865 and it gave its name to a class of meteorites called shergottites. A shergottite named EETA79001 was found in Antarctica in 1979 and has an elemental composition even closer to Bounce Rock's. Those two and about 18 other meteorites found on Earth are believed to have been ejected from Mars by the impacts of large asteroids or comets hitting Mars.
Opportunity's miniature thermal emission spectrometer indicates that the main ingredient in Bounce Rock is a volcanic mineral called pyroxene, said science-team collaborator Deanne Rogers of Arizona State University, Tempe. The Moessbauer spectrometer also identified pyroxene in the rock. The high proportion of pyroxene makes it unlike not only any other rock studied by Opportunity or Spirit, but also unlike the volcanic deposits mapped extensively around Mars by a similar spectrometer on NASA's Mars Global Surveyor orbiter, Rogers said.
Thermal infrared imaging by another orbiter, Mars Odyssey, suggests a possible origin for Bounce Rock. An impact crater about 25 kilometers wide (16 miles wide) lies about 50 kilometers (31 miles) southwest of Opportunity. The images show that some rocks thrown outward by the impact that formed that crater flew as far as the distance to the rover. "Some of us think Bounce Rock could have been ejected from this crater," Rogers said.
Opportunity is driving eastward, toward a crater dubbed "Endurance" that might offer access to thicker exposures of bedrock than the rover has been able to examine so far. With new software to improve mobility performance, the rover may reach Endurance within two weeks, said JPL's Jan Chodas, flight software manager for both Mars Exploration Rovers.
Mission controllers at JPL successfully sent new versions of flight software to both rovers. Spirit switched to the new version successfully on Monday, and Opportunity did late Tuesday.
A parting look at the small crater in which Opportunity landed is part of a full 360-degree color panorama released at the news conference. The view combines about 600 individual frames from the rover's panoramic camera, said science-team collaborator Jason Soderblom of Cornell University, Ithaca, N.Y. It is called the Lion King panorama because it was taken from a high-ground viewpoint at the edge of the crater, like the high-ground viewpoint used by animal characters in the Lion King story.
The panorama gives a good sense of how wind has uncovered the outcrop at the upwind side of the crater and deposited sand in the downwind side of the crater and bright martian dust in the wind shadow of the crater, Soderblom commented. On the wide plain outside the crater lies Bounce Rock.
JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA's Office of Space Science, Washington, D.C. Images and additional information about the project are available from JPL at
http://marsrovers.jpl.nasa.gov
and from Cornell University, Ithaca, N.Y., at
http://athena.cornell.edu/ .
-end-
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What next? Mars rover finds rock that looks just like a man's thingy?
If you want to do something useful with your 'oh so blooming wonderful' Mars rover, why not drive over to where our much humbler British effort is languishing and give the bloody thing a kick.
</rant>
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It'd be nice if they rovers COULD do that, unfortunately with the limited lifespan of these rovers, I doubt they could make it out to whereever beagle 2 might have hit. Never mind that it's likely beagle 2 crashed into the surface of the planet at high velocity, and that it's likely theres not much left to be fixed/examined/"kicked".
Just because you're unhappy that the US Rovers survived, and the british rover didn't, is no reason to insult the science thats being done.
Robin G Hewitt wrote:

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Do I see sour grapes? Gee dude, we all lose probes. God knows the U.S. has lost its share. Get over it. Your next one will be that much better. Perhaps it will land without cracking up. Whether it works afterwards is anyone's guess.
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George wrote:

Yeah, and how many astronauts died on Beagle 2? We lost seven just a year ago. And he has the nerve to rant?
--
Greg Crinklaw
Astronomical Software Developer
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Of course you do, it was a real disappointment when it disappeared. Did I ever claim superhuman qualities?

Uh? Lost me there, what has that got to do with it?
It was not actually a serious request for assistance. Personally I am intrigued by the revelations emerging from the red planet, but why do I have to read them on comp.robotics.misc?
Whatever. You will probably continue to cross post across the groups, I probably won't continue to rant.
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Only Astronomers and their astrologer friends lose probes. The rest us simply lose time, working around NASA to crap to see if the French got any rockets that work.
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Whatever you say, ZZ.
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wrote:

True, Beagle 2 blew chunks, but you have a great orbiter. It blows something much nicer. Like, I donno, I suppose maybe Brit hottie Keira Knightly
http://after-thursday.org/beautiful/images2/keiraknightly4.jpg
So add the two together and things pretty much cancel out to neutral or positive.
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Beagle == Lawn Dart

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Ron wrote:

Even if the rocks have similar spectra, I'm still puzzled by the rarity of rocks on Mars matching the Martian meteorites. A couple possibilities:
(1) We've seen very little of the Martian surface, and what we have seen has been selected for ease of landing. The rocks we're looking for are abundant on most other parts of Mars.
(2) There are lots of Martian meteorites on Earth, but only this one class has been identified; the rest are indistinguishable from "ordinary" meteorites (and presumably have lost any Martian gas that was trapped in them).
(3) The putative Martian aren't Martian.
OK, that was three possibilities. Comments?
Mike McSwell
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Well, yeah, I have a couple. Actually, we have photographed nearly all if not all of the Martian surface, so to say that we've only seen a little is really an over-simplification. Secondly, What we have seen indicates that Mars has quite a diverse range of rock types, compared to the moon, for instance, and many other bodies in our solar system, with the exception of the earth. So it doesn't surprise me at all that it has taken so long to come up with a match with Martian meteorites found on earth. The fact that they found a rock on Mars that so closely matches one found on Earth is really astonishing, in my view. Finally, number of meteorites that have been found that didn't originate from Mars vastly outnumber the number of meteorites that did. There really aren't as many Mars meteorites as your might think. The chances that they would have matched up these two rocks is likely to be much lower than finding the proverbial needle in a haystack.
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snipped-for-privacy@george.net says...

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Doug... wrote:

OK, that reinforces my question: if these types of rocks are so rare at the surface on Mars, how come they're the _only_ Martian meteorites we find on Earth? (I didn't realize you should be able to recognize these rocks from orbit; I was assuming you had to be on the ground.)

But an impact that launches deep rocks will also launch surface rocks, right? Some of these might melt and therefore become indistinguishable from other meteorites, maybe (at least they would lose their gases), but some would not, I would think. Why don't we find meteorites which represent surface Martian rocks? (Or do we, and we just haven't recognized them?)
George wrote:

I understand that--what I don't understand is why the only Martian meteorites we've found on Earth turn out to be rare rocks on Mars (unless, as you say, they're from deep in Mars).
Mike Maxwell
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says...

Easy answer is that they are not the only Martian meteorites found on earth. There are at least three different types known.
http://en.wikipedia.org/wiki/Martian_meteorite Mars meteorites include three rare groups of achondritic (stony) meteorites (16 objects total) with isotope ratios that are said to be consistent with each other and inconsistent with the earth. It should be pointed out, however, that the isotope ratios do not actually match Mars ratios especially well, to the extent that Mars ratios are known, although they do differ substantially from Earth isotope ratios and from what is known of Lunar ratios.
All the meteorites are igneous rocks. Lherzolitic shergottites (one from Antarctica, two from California) are identified by their Deuterium/Hydrogen ratios. The crystals appear to be 154-187 million years old and they appear, from cosmic ray analysis, to have spent 2.5 to 3.6 million years in space. There are also basaltic shergottites, some of which appear (from the presence of hydrated carbonates and sulfates) to have been exposed to liquid water prior to injection into space. One of the shergottites, known as ALH84001, is much older than the others - about 4.5 billion years. In this respect, it resembles a typical meteorite rather than the other shergottites. The other two types of Martian meteorites are Chassignites and Nakhlites. All appear to have been on earth no more than 35,000 years. Together, these objects are called SNC meteorites.

I won't pretend to have all the answers, when it comes to meteorites, since they are not my specialty. Having said that, here is a list of the known Mars meteorites, an information about them:
http://www2.jpl.nasa.gov/snc /

Considering that we've only scratched the surface, literally, of Mars, I don't hink any scientist would make the claim that they are rare on the surface simply because we don't know anything about their abundance there.
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says...

They're *not* the only Martian rocks we find on Earth. There are three general classifications of Martian meteorites that have been found here, and Bounce Rock falls into one of them. The other two are closer to what's been seen from orbit and on the surface -- though one of the classifications has more carbonates than what we've been seeing on Mars.
And of course you can recognize some elements of minerology from orbit -- how else do you think the MER planners figured out that there was hematite at the Meridiani Planum site? In fact, that site was called the Hematite Site during the landing site selection process.

A rock melt doesn't necessarily lose its gasses -- it incorporates the gasses in the environment in which the melt occurred.
Now, most of the Martian meteorites do not *seem* to be impact melts -- they mostly look like highly shocked varieties of volcanic rocks. But as anyone who has studied the examination of the lunar samples knows, it can be very difficult to tell between impact melts and volcanic rocks. Much of the impact melt sampled at Fra Mauro on the Moon, for example, is basaltic in nature -- but still seems to be impact melt.
Of course, very energetic impacts *do* toss around both surface rocks and deep crustal materials. I'm tempted to think that the Martian meteorites we've seen were ejected in basin-forming impacts, since those generate the most energy. But the exact dynamics of how such meteorites are ejected entirely from Mars' gravity well are poorly understood -- perhaps those dynamics select either surface rocks or deeper crustal rocks for ejection out of Mars' grasp. I don't think anyone has a model that can predict that with very much accuracy.

Again -- there are more than one type of Martian meteorites. Granted, none of them seem *extremely* abundant on the Martian surface, but then again, we don't know exactly when they were ejected from Mars. There are guesses, but they're not pinned down all that well.
Doug snipped-for-privacy@NOSPAM.mn.rr.com
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Don't forget that the meteorites are all relatively recent arrivals, simply because recently-arrived meteorites are the ones that are recognizable as meteorites. They may well be derived from only one or two major impacts on Mars, i.e. from the rocks at one or two points on Mars. So it is not too surprising if they're not typical of the surface; we're seeing a very small and not necessarily representative sample.

Remember also that major impacts excavate rocks from substantial depths, and what we've seen -- either from orbit or close up -- is almost entirely just the surface layer.

The oxygen-isotope ratios, which are fairly distinctive, should be shared by pretty much any rock from Mars.

Grossly implausible, given that the gas trapped in bubbles in a couple of them is unmistakably Martian air.
--
MOST launched 30 June; science observations running | Henry Spencer
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