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Meteorite from Mars is in a class of its own

Jenny Winder, News Writer
Jan 7, 2013, 0:00 UTC

Sen—It weighs only about 11 ounces (320 grams) but this small lump of rock is big news. Found in the Sahara desert in 2011 it was designated Northwest Africa (NWA) 7034, but nicknamed "Black Beauty". It has now undergone a year of intense scrutiny and researchers have concluded that NWA 7034 is unlike any other Martian meteorite.

It formed 2.1 billion years ago at the start of the most recent geologic period on Mars, known as the Amazonian. This makes it significantly older than any previous specimen. Its composition is different and it contains 10 times more water than any previously studied Martian meteorite. It may be the first discovered from the Martian surface or crust as it matches surface rocks and outcrops studied by NASA rovers and orbiters.

Most Martian meteorites are divided into three types, named after three meteorites: Shergotty, Nakhla, and Chassigny. There are about 110 Martian meteorites, though their point of origin on Mars is not known and recent data from lander and orbiter missions suggest they are a mismatch for the Martian crust. Although NWA 7034 has similarities to SNC meteorites, including the presence of macromolecular organic carbon, this new meteorite has many unique characteristics which put it in a class of its own. NWA 7034 is made of cemented fragments of basalt, rock that forms from rapidly cooled lava. The fragments are mostly feldspar and pyroxene, most likely from volcanic activity.

"This Martian meteorite has everything in its composition that you'd want in order to further our understanding of the Red Planet," said Carl Agee, leader of the analysis team and director and curator at the University of New Mexico's Institute of Meteoritics in Albuquerque. "This unique meteorite tells us what volcanism was like on Mars 2 billion years ago. It also gives us a glimpse of ancient surface and environmental conditions on Mars that no other meteorite has ever offered."

The large amount of water contained in NWA 7034 may have originated from interaction of the rocks and water in Mars' crust. The meteorite also has a different mixture of oxygen isotopes than has been found in other Martian meteorites, which could be from interaction with the Martian atmosphere.

"The texture of the NWA meteorite is not like any of the SNC meteorites," said co-author Andrew Steele, who led the carbon analysis at the Carnegie Institution's Geophysical Laboratory. "This is an exciting measurement in Mars and planetary science. We now have more context than ever before to understanding where they may come from."