Image: NWA 7325
© Stefan Ralew / SR Meteorites
This is the largest fragment of meteorite NWA 7325, recovered in Morocco in 2012 and purchased by German meteorite dealer Stefan Ralew. Scientists say it's possible that the rock was struck off from the planet Mercury.
Universe Today
updated 2/5/2013 9:31:55 PM ET 2013-02-06T02:31:55

Pieces of the Moon and Mars have been found on Earth before, as well as chunks of Vesta and other asteroids — but what about the innermost planet, Mercury? That’s where some researchers think this greenish meteorite may have originated, based on its curious composition and the most recent data from NASA’s Messenger spacecraft.

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NWA 7325 is the name for a meteorite fall that was spotted in southern Morocco in 2012, comprising 35 fragments totaling about 345 grams. The dark green stones were purchased by meteorite dealer Stefan Ralew, who operates the retail site SR Meteorites. Ralew immediately made note of the rocks' deep colors and lustrous, glassy exteriors.

Ralew sent samples of NWA 7325 to researcher Anthony Irving of the University of Washington, a specialist in meteorites of planetary origin. Irving found that the fragments contained surprisingly little iron but considerable amounts of magnesium, aluminum and calcium silicates — in line with what’s been observed by Messenger in the surface crust of Mercury.

Even though the ratio of calcium silicates is higher than what’s found on Mercury today, Irving speculates that the fragments of NWA 7325 could have come from a deeper part of Mercury’s crust, excavated by a powerful impact event and launched into space, eventually finding their way to Earth.

In addition, exposure to solar radiation for an unknown period of time and shock from its formation could have altered the meteorite’s composition somewhat, making it not exactly match up with measurements from Messenger. If this is indeed a piece of our solar system’s innermost planet, it will be the first Mercury meteorite ever confirmed.

But the only way to know for sure, according to a research paper written by Irving and his colleagues, is to conduct further studies on the fragments and, ultimately, samples that are returned from Mercury.

Irving’s team’s findings on NWA 7325 will be presented at the 44th Lunar and Planetary Science Conference, to be held in Houston from March 18 to 22. Read more in this Sky & Telescope article by Kelly Beatty.

More about meteorites:

Jason Major is a graphic designer living in Providence, R.I. He writes about astronomy and space exploration on his blog Lights in the Dark, for Discovery News and for Universe Today. This report originally appeared on the Universe Today website on Feb. 4, with the headline "Is This Meteorite a Piece of Mercury?"

Copyright © 2013 Universe Today. Republished with permission.

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Photos: Messenger at Mercury

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  1. First views from orbit

    NASA's Messenger probe is the first spacecraft to orbit the planet Mercury, and it sent back the first pictures taken from orbit on March 29, 2011. This view looks across Mercury's pockmarked surface toward the planet's horizon. Bright rays from Hokusai Crater can be seen running north to south. (NASA / JHU / CIW) Back to slideshow navigation
  2. In living color

    Mercury isn't exactly the solar system's most colorful planet, but you can make out subtle shades in this first color image from Messenger. Major craters on Mercury are named after artists, authors, composers and other creative figures from history. The dominant crater in the picture is known as Debussy. (NASA / JHU / CIW) Back to slideshow navigation
  3. Who's where

    This chart shows you the names of notable features in the first picture ever taken by a spacecraft orbiting Mercury. The triangle indicates an area of the planet that had never been imaged before. (NASA / JHU / CIW) Back to slideshow navigation
  4. Debussy up close

    A narrow-angle image from NASA's Messenger orbiter focuses in on Debussy Crater, the bright feature at the top of the frame. The bright rays consist of material ejected by the massive impact that created Debussy, and extend for hundreds of miles. (NASA / JHU / CIW) Back to slideshow navigation
  5. Way up north

    This Messenger picture shows a heavily cratered region near Mercury's north pole, as seen from an altitude of about 280 miles. The region had never been imaged before. Previous up-close views of Mercury came from flybys, including the Mariner 10 mission in the 1970s and Messenger's pre-orbital encounters. (NASA / JHU / CIW) Back to slideshow navigation
  6. Craters upon craters

    This picture of southern terrain on Mercury illustrates what Messenger chief scientist Sean Solomon means when he says "there are so many craters they start to obscure one another." (NASA / JHU / CIW) Back to slideshow navigation
  7. Simply beautiful

    The crater near the bottom of this Messenger image is a beautiful example of a relatively small, simple, fresh impact feature on Mercury. The crater is nearly bowl-shaped, with just a small flat area in the center of its floor. The bright ejecta and rays are symmetrically distributed around the crater, indicating that the body that struck Mercury to form the crater approached on a path that was not highly inclined from the vertical. (NASA / JHU / CIW) Back to slideshow navigation
  8. Wide-angle view

    Messenger's Wide Angle Camera is not your typical color camera. It is sensitive to 11 bands of color, in visible through near-infrared wavelengths. This WAC image shows several craters on Mercury, with bright rays from Hokusai Crater (to the north) crossing through the scene. (NASA / JHU / CIW) Back to slideshow navigation
  9. Smooth plains

    This Messenger image shows an area of Mercury that had not been previously imaged, in Mercury's north polar region. The smooth terrain is pockmarked by craters that cast long shadows. Understanding the interiors of such craters and any ices they may contain is one of the Messenger mission's main science goals. (NASA / JHU / CIW) Back to slideshow navigation
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  1. NASA / JHU / CIW
    Above: Slideshow (9) Marvels from Mercury
  2. Image:
    Y. Beletsky / ESO
    Slideshow (12) Month in Space: January 2014


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