Planet Mercury comes to Peabody

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Photo by Hailey Winston.

A walnut-sized rock, first noticed in the Moroccan desert for its greenish tint, now perches on a rotating display in the Yale Peabody Museum of Natural History as potentially the first known meteorite from Mercury to ever strike earth.

The meteorite is the centerpiece of a new Peabody exhibit, “From Mercury to Earth? A Meteorite Like No Other,” which opens today and runs through Sept. 2, 2014. The asteroid, discovered in early 2012 by Moroccan nomads, is one of 35 fragments of a more than 3 pound rock that shattered as it flew to earth.

“I’m very excited thing[s] came together the way that they did,” said Stefan Nicolescu, the museum’s mineralogy curator.

The meteorite is unique for multiple reasons, including its exceptionally low iron content. This feature attracted the attention of Tony Irving, a professor of earth and space sciences at the University of Washington. Irving analyzed a sample of the rock from Stefan Ralew, a meteorite enthusiast who had traveled to Morocco and purchased more than a dozen of the fragments.

Ralew, who is also a photographer, said he was initially ambivalent about purchasing the samples, but was persuaded by the rock’s earthy green tint. The green color is unusual for most meteorites because the presence of iron causes them to have darker coloration, but the low iron content of this sample allows the green color of the chromium to show through.

Analysis of a sample at MIT revealed that its iron to silicon ratio is nearly identical to the ratio reported by a recent probe to Mercury, which Irving said is strong evidence for it coming from that planet. Mercury also has a relatively strong gravitational field, and the massive fractures on the rock suggest it may have been ejected by a force strong enough to fling it from the planet.

But Irving added it is always possible that these clues are pointing to the wrong conclusion.

“Unfortunately, I can’t tell you with absolute certainty that the rock is from Mercury,” Irving said. “But if it isn’t, it’s from a very interesting place.”

All known meteorites come from the Moon, Mars or asteroid belt, and this would be the first one to not to originate from any of these sources. Irving speculated the sample is old enough that it could have come from a planet in the early solar system.

Director of the Peabody Derek Briggs said he is excited, and anticipates the exhibit will attract wide attention because of the asteroid’s novelty.

Irving said he thinks the recent rise of private meteorite collectors bodes well for the field — the number of meteorite discoveries has dramatically increased since the advent of the Moroccan trade, which is now responsible for about half of meteorite discoveries each year.

The meteorite is currently on loan from Ralew.

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