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article imageGreen meteorite NWA 7325 found in Morocco may be from Mercury

By JohnThomas Didymus     Mar 31, 2013 in Science
Scientists say they have discovered what could be the first known meteorite from Mercury. Scientist Anthony Irving, speaking said at the 44th annual Lunar and Planetary Science Conference said that a rock found last year could have come from Mercury.
Space.com reports that according to Irving speaking at the 44th annual Lunar and Planetary Science Conference in The Woodlands, Texas, studies suggest that the green rock NWA 7325 found in Morocco last year came from Mercury and not from an asteroid or the planet Mars.
Meteorite scientists say NWA 7325 is actually a clutch consisting of 35 meteorite samples discovered in 2012 in Morocco. Irving and his colleagues have dated the rocks at about 4.56 billion years.
According to Sky and Telescope, the meteorites originated from a German dealer Stefan Ralew, who purchased the rocks found a few months earlier in the Moroccan desert. Sky and Telescope reports Ralew said he could see immediately that the rocks were unusual with a greenish color. He said: "Green and glassy fusion crusts are known from a few lunar meteorites, but they all don't have an extreme color as this one."
Ralew sent the Moroccan meteorites, dubbed Northwest Africa 7325, to the laboratory of Anthony Irving, a scientist noted for his expertise with unusual meteorites. According to Space.com, Irving is an expert at the University of Washington and has been studying meteorites for years. But NWA 7325 was not like any other meteorite he had seen.
NWA 7325
NWA 7325
Stefan Ralew/
Sky and Telescope reports that after he saw the samples, Irwing said: "NWA 7325 is tantalizing, and certainly more consistent with the Messenger results than either angrites or aubrites, but we need a [spacecraft-returned sample] for 'ground truth.'"
Messenger is a spacecraft orbiting Mars and conducting a close observation of the surface of the planet.
Space.com reports Irving said at the conference: "It might be a sample from Mercury, or it might be a sample from a body smaller than Mercury but [which] is like Mercury."
According to Irving, a powerful impact probably ejected NWA 7325 out from Mercury to Earth.
Experts are able to identify meteorites from Mars because they carry traces of materials from the Martian atmosphere. Experts have also characterized rocks from some of the largest asteroids such as Vesta which have distinct chemical properties.
The unique properties of NWA 7325 which match the unique composition of Mercury as detailed by Messenger suggested to scientists that it originated from Mercury.
Irving suggests that the meteorite was formed and ejected either from Mercury or from a planet or other space body that had flowing magma on its surface at some time in its history.
Some of NWA 7325's properties that suggest it originated from Mercury include its magnetic intensity which was found to be extremely low. Rocks derive their magnetic intensity from their parent body. Earth rocks for instance have a characteristic magnetic intensity that can be used to identify them. NWA 7325's low magnetic intensity matched data sent from NASA's Messenger spacecraft that shows that Mercury has a low magnetic intensity that resembles NWA 7325.
Other data from Messenger about Mercury's geological and chemical composition suggest the planet is low in iron. The meteorite was also found to be low in iron. When considered along with the fact that the meteorite does not have properties identifying it with Mars, experts are confident that it is from Mercury or a space body very similar to Mercury.
Messenger's mission to Mercury expired recently, but the science team has requested for an extension of the mission until 2015. The extension will allow time to gather more data that could confirm Irving's conclusions about NWA 7325.
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