Martian meteorite NWA 7034 weighs approximately 320 grams (11 ounces). Credit: NASA
A 2-billion-year-old rock found in the Sahara desert has been identified as a meteorite from Mars’ crust, and it contains ten times more water than any other Martian meteorite found on Earth. It also contains organic carbon. The age of the rock, called NWA 7034, would put its origins in the early era of the most recent geologic epoch on Mars, the Amazonian epoch. While its composition is different from any previously studied Martian meteorite, NASA says it matches surface rocks and outcrops that have been studied by Mars rovers and Mars-orbiting satellites.
“The contents of this meteorite may challenge many long held notions about Martian geology,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate in Washington. “These findings also present an important reference frame for the Curiosity rover as it searches for reduced organics in the minerals exposed in the bedrock of Gale Crater.”
This new class of meteorite was found in 2011 in the Sahara Desert. Designated Northwest Africa (NWA) 7034, and nicknamed “Black Beauty,” it weighs approximately 320 grams (11 ounces). Research teams from the University of New Mexico, the University of California at San Diego and the Carnegie Institution in Washington analyzed mineral and chemical composition, age, and water content.
NWA 7034 is made of cemented fragments of basalt, rock that forms from rapidly cooled lava. The fragments are primarily 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.”
There are about one hundred Martian meteorites that have been collected on Earth. They were all likely blasted off the Red Planet by either an asteroid or comet impact, and then spent millions of years traveling through space before falling to Earth.
Researchers theorize the large amount of water contained in NWA 7034 may have originated from interaction of the rocks with water present in Mars’ crust. The meteorite also has a different mixture of oxygen isotopes than has been found in other Martian meteorites, which could have resulted from interaction with the Martian atmosphere.
Scientists say the age of NWA 7034 is important because it is much older than most other Martian meteorites.
“We now have insight into a piece of Mars’ history at a critical time in its evolution,” said Mitch Schulte, program scientist for the Mars Exploration Program at NASA Headquarters.
Most Martian meteorites are divided into three rock types, named after three meteorites; Shergotty, Nakhla, and Chassigny. These “SNC” meteorites currently number about 110. 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 the SNC meteorites, including the presence of macromolecular organic carbon, this new meteorite has many unique characteristics.
“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.”
This article was updated on 1/4/13.