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New Mars Meteorite Found in California
New Mars Meteorite Found in California
30 Jan 2000
(Source: Jet Propulsion Laboratory)

By Ron Baalke
http://www.jpl.nasa.gov/snc/la.html

I'm very pleased to report on a new Mars meteorite find by a good friend and fellow meteorite collector, Bob Verish. The meteorite was found somewhere in the Mojave Desert in California, and consists of two stones of 452.6 & 245.4 grams. The two rocks have been classified as Mars meteorites, specifically basaltic shergottites, by analysis done at UCLA. The new meteorite's official name is the Los Angeles meteorite.

Background

While on a rock collecting trip somewhere in the Mojave Desert in California, Bob Verish picked up a couple of rocks that had caught his eye. The rocks were basaltic with dark exteriors on top, and were interesting enough to his discerning eye to be included in his rock collection.

About 20 years would pass before Bob would look closely at the rocks again.

The rocks were stored in boxes in Bob's backyard along with a large portion of his rock collection. On October 30, 1999, while clearing out his rock collection for rat nests and rodent dropping, Bob came across the rocks again. Since Bob had begun collecting meteorites about 5 years ago, he knew what meteorites looked like. He immediately noted the dark fusion crust on the rocks and suspected the two rocks to be meteorites. Bob cut off small samples of each rock (total weight of about 30 grams) which he would then take to Alan Rubin at UCLA for analysis.

New Mars Meteorite?

On December 17, 1999, UCLA confirmed the two rocks were meteorites. They also noted that upon viewing a thin section of the rocks, they bore a remarkable similarity with the QUE 94201 meteorite, a Mars meteorite found in the Antarctic in 1994. They suspected the rocks to also be Mars meteorites, but would require additional lab analysis for confirmation.

Shortly aftwards, a very excited Bob brought the rocks to me. Bob has brought many rocks to me over the years, rocks that were potential meteorite candidates, though many of them turned out be "meteorwrongs". Bob informed me of the preliminary identification of the rocks as Mars meteorites (shergotittes) by UCLA. I took several photographs of the meteorites which are shown here on this web page (http://www.jpl.nasa.gov/snc/la.html). UCLA were busy analyzing the rocks though the Christmas break and wanted to submit papers on the meteorites for the upcoming Lunar And Planetary Science Conference (LPSC) being held in Houston in mid-March. The abstract deadline for the conference was January 12, 2000. UCLA was working hard to have confirmation of the rocks done by then, and had enlisted the help of Arizona State University.

Mars Meteorite Confirmed

By January 12, UCLA had confirmed the rocks were indeed Mars meteorites and had submitted three abstracts for the LPSC [1][2][3]. Meanwhile, Bob had reported his meteorite find to the Meteoritical Society, and the Nonmenclature Committee of the Meteoritical Society approved the name of Los Angeles for the newly discovered Mars rocks. Bob has affectionately nicknamed the two Mars rocks as "Miguel" and "Gabriel".

In the petrology analysis led by Alan Rubin [1], the Martian origin for the Los Angeles meteorite was indicated by the D/H ratio. Apatite grains from the meteorite contained D-enriched water that was isotopically indistinguishable from comparable minerals from other shergotites. The rocks were shocked, which was also consistent with Mars meteorites. In the geochemistry analysis led by James Greenwood [2], the Los Angeles meteorite showed characteristic Martian values for such ratios as Mn/Fe, Na/Al and Ga/Al. It was also noted that the Los Angeles in many respects was the most geochemically evolved sample yet discovered from Mars.

Per Bob Verish [4], the following paragraph is a proposed draft of what is proposed to appear in the Meteoritical Bulletin 84: Final version, 2000, July, MAPS 35:

Los Angeles (original find location unknown)
Los Angeles County, California, USA
Recognized 1999 October 30
Martian basalt (shergottite)
Two stones, weighing 452.6 g and 245.4 g respectively, were found by Bob Verish in his back yard while he was cleaning out a box of rocks that was part of his rock collection. The specimens may have been collected ~20 years ago in the Mojave Desert. Classification and mineralogy (A. Rubin, P. Warren and J. Greenwood, UCLA): a basalt with a texture closely resembling that of the QUE 94201; plagioclase laths, 43.6 vol%, An41Or4 to An58Or1, have been shocked to maskelynite; Ca-pyroxene, 37.7 vol%, ranges from Fs45Wo13 to Fs45Wo37 to Fs72Wo24; other mineral modes, 4.9 vol% silica, 4.2 vol% fayalite, 2.4 vol% K-rich felsic glass, 3.5 vol% titanomagnetite, 2.7 vol% Ca phosphate (including whitlockite and chlorapatite), 0.7 vol% pyrrhotite, and 0.2 vol% ilmenite; contains a higher proportion of plagioclase than Shergotty or Zagami, and has pyroxene that is moderately more ferroan than that in QUE 94201. Specimens: main masses with finder; 30 g, UCLA. [Houston LPSC references to be added later]
More Mars Meteorites?

I personally believe there are more unidentified Mars and lunar meteorite sitting in collections waiting to be discovered. However, finding a new Mars meteorite is not an easy feat as Mars meteorites are extremely rare. Assuming the two Mars meteorites found in the Sahara Desert are paired, and the two new Los Angeles rocks are also paired, then the number of Mars meteorites is at only 14. Compare that with the over 20,000 meteorites found on Earth. The Los Angeles meteorite is only the second Mars meteorite found in the United States. The other US find was the Lafayette meteorite found in Indiana. Like the Los Angeles meteorite, the Lafayette meteorite sat in a collection for a number of years before it was recognized as a Mars meteorite. In Lafayette's case, it was discovered in the geological collection at Purdue University, and identified as a Mars meteorite in 1931. There is a lot of work involved in identifying meteorites. Since 99% of the rocks brought in by the public turn out not to be meteorites, weeding through all of these "meteorwrongs" takes a lot of time and effort. But as the Los Angeles meteorite shows, the effort can sometimes be worth it.

References

  1. Rubin A. et al, "The Pretology Of Los Angeles: A New Basaltic Shergottite Find", 31st Lunar And Planetary Science Conference (http://cass.jsc.nasa.gov/meetings/LPSC2000/)
  2. Warren P. et. al, "Geochemistry Of Los Angeles, A Ferroan, La- and Th-Rich Basalt From Mars", 31st Lunar And Planetary Science Conference.
  3. Greenwood J. et. al, "Late-Stage Crystallization Features Of Los Angeles, A New Balsatic Shergottite", 31st Lunar And Planetary Science Conference.
  4. Verish, Robert, The Los Angeles Meteorite Home Page (http://members.tripod.com/~marzmeteorite/la/losangel.htm)
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