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Posted on 03/12/2008 5:19:46 PM PDT by blam
Mysterious Meteorites Stymie Scientists
Anne Minard
for National Geographic News
March 12, 2008
A pair of mysterious meteorites discovered in Antarctica is baffling scientists who are struggling to determine the origin of the space rocks.
The meteorites, dubbed GRA 06128 and GRA 06129, were found in the Graves Nunataks region of Antarctica in 2006 (see an interactive map of Antarctica).
The rocks were oddly rusty and salty and smelled like rotten eggs, its discoverers said.
Initially, a team at the University of New Mexico (UNM) caused a stir when its analysis hinted that the pair may hail from Venus or the moon.
But other teams then hurried to get pieces of the space rocks for analyses of their own—and for the most part, they disagree.
GRA 06128 looks like rocks retrieved from the lunar highlands by the Apollo 16 astronauts in 1972, but it contains much more sodium, research has shown.
The rock is also much older than the Venusian surface, according to the newer analysis, thereby eliminating that possibility.
The identity of the meteorites' source remains exciting and mysterious, said Allan Treiman, a scientist with the Lunar and Planetary Institute in Houston who led one of the recent investigations of the rocks.
"From what has been reported so far, it's pretty clear that the meteorite is not from the Earth, or the moon, or Venus, or any of the common sources of meteorites," he said. "It's much harder to know where it is from."
Both teams—along with three others—are presenting findings about the meteorites at the 39th Lunar and Planetary Science Conference in Houston this week.
Not of This World?
GRA 06128 and its mate are slab-shaped, gray rocks containing bits of black glass.
One of the first teams to get a sample of the meteorites was led by UNM's Chip Shearer.
The researchers analyzed chemical signatures called isotopes and initially determined that the meteorites came from Earth or the moon, a position they've since retooled.
"Although initial oxygen isotopic compositions are consistent with an origin in the Earth-Moon system, numerous observations appear to eliminate both bodies," Shearer and his team write in an abstract presented at this week's meeting.
Doug Rumble from the Carnegie Institution and his colleagues will also present an analysis of GRA 06128 and 06129 at the conference.
He said the New Mexico researchers initially studied a "tiny crumb that fell off the outside" of GRA 06129, but they didn't wash the outer layer to remove any Earthly weathering agents that might alter the findings.
"The UNM analytical results reflect only imperfectly the actual extraterrestrial composition of the meteorite, because UNM also analyzed rust that formed as the meteorite lay exposed to Earth's atmosphere," he said.
Rumble's own analysis puts the meteorites "right in the range of values expected for rare meteorites called brachinites," he said.
Brachinites are believed to be the remnants of planets that once orbited between Mars and Jupiter (see an interactive map of the solar system).
"So now we are all meeting in Houston to hang our heads a little and admit to one another that maybe we were a little too hasty," Rumble said, "and got too excited over an unwashed meteorite."
Unsettled Debate David Kring, a visiting scientist at Houston's Lunar and Planetary Institute and a co-author on Treiman's paper, said there's still work to be done to nail down the exact nature of the meteorite pair.
The chemical and mineral compositions of the rocks are similar to brachinites and another type of meteorite called chondrites, he said.
Chondrites, leftovers from the formation of asteroids, are the most common meteorites. But the pair doesn't match either category exactly, Kring said.
The rocks are partially melted, which is not characteristic of chondrites.
And they contain high levels of the mineral feldspar, which is not typically associated with the short-lived planets between Mars and Jupiter.
"Thus there are two mysteries," Kring said. "What is the parent planet for the rock, and what type of geologic activity on that planet produced the unusual mineral assemblage?"
There is no shortage of new ideas to account for the disparity.
"My preferred working hypothesis is that [the meteorites] actually represent a piece of crust from an asteroidal body—the surface of another planet, if you like," offered James Day, a geologist at the University of Maryland.
Day has joined the other researchers at this week's meeting to puzzle over the rocks.
Treiman added that it would take a very large asteroid or a dwarf planet to cause the melting seen in the meteorites.
Whether or not its home is discovered, GRA 06128 is a "pretty puzzle, and will help us understand how asteroids form and how they evolve to become planets," he said.
Now that was funny!
I should have known you’d have posted this. :’)
Astronomy Picture of the Day 12-26-02
[”Searching for Meteorites in Antarctica”]
NASA | 12-26-02 | Robert Nemiroff and Jerry Bonnell
Posted on 12/25/2002 10:07:14 PM PST by petuniasevan
http://www.freerepublic.com/focus/f-chat/812313/posts
Giant Crater Found [in Antarctica]:
Tied to Worst Mass Extinction Ever [Permo-Triassic]
SPACE.com | June 2, 2006 | Robert Roy Britt
Posted on 06/02/2006 11:44:43 AM PDT by cogitator
http://www.freerepublic.com/focus/f-news/1642426/posts
Does a giant crater lie beneath the Antarctic ice?
nature news | 2 06 | Mark Peplow
Posted on 06/05/2006 9:07:10 AM PDT by S0122017
http://www.freerepublic.com/focus/f-chat/1643681/posts
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Is it the “Locnar?”
Yeah...watch it. I work my fingers to the bone and you....
Hey, ever heard of pingin’ me buster? ;’)
I found this while foolin’ around a while ago:
[rummages around]
Okay, forget it, can’t find it now. But it was high larry us.
that rotten egg smell makes me think of a volcano - maybe the rocks they found were ejected from this, in 2004?
http://earthsciencesus.blogspot.com/2008/01/volcanic-heating-is-melting-ice-caps.html
ANTARCTICA - no name volcano
June 20th, 2004
A previously unknown underwater volcano has been discovered off the coast of Antarctica, and explains mariners’ historical reports of discolored water in the area. The research vessel Lawrence M. Gould (information sheet illustrating the ship ) was returning from a study of a collapsed ice self when it passed over the volcano. Temperature probes showed evidence of geothermal heating of seawater. A lack of marine life on dark rock around the volcano indicated that lava had flowed fairly recently. The volcano is in an area known as Antarctic Sound, at the northernmost tip of Antarctica. There is no previous scientific record of active volcanoes in the region where the new peak was discovered. The volcano is located on the continental shelf, in the vicinity of a deep trough carved out by glaciers passing across the sea floor. The volcano stands 2,300 feet above the sea floor and extends to within roughly 900 feet of the ocean surface.
Very interesting, could be a topic, hmm, maybe worth a search.
Semi-related sidebar:
In an article in the now-defunct “Strange” magazine, Vincent Gaddis recounted how a vessel charted and landed on an island in the southern Pacific (if memory serves, it was east of Africa), one of three smallish islands in a group. They landed to either hunt or butcher something (whales, seals, I forget) and didn’t think much of it.
There’s nothing there today.
Apparently the boulders sticking up were merely carried along in big icebergs, or some islands have subsequently sunk. S’cool.
Fragments of the Death Star?
...reminds me of Heyerdahl, expecting to find a small island somewhere in the Pacific as shown on an old map, to break the raft’s journey, and finding nothing but breakers crashing over a submerged reef.
Yeah, that showed some daring — perhaps because of high tide, perhaps because the slightly submerged chunk of land had vanished, the Heyerdahl raft and crew passed right over the charted position. I wouldn’t have tried that one. :’)
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