U.S. scientists have identified a new class of meteorite that fell to Earth and likely originated from the crust of the Red Planet.
The meteorite Northwest Africa 7034 (NWA 7034 for short), nearly 11 ounces (320 grams) in weight, was found in the Saharan Desert in Marocco in 2011.
Now the team led by Dr Carl Agee of the University of New Mexico’s Institute of Meteoritics in Albuquerque has determined that the meteorite formed 2.1 billion years ago, the early era of the most recent geologic epoch on Mars called the Amazonian.
NWA 7034 was found to contain an order of magnitude more water than any other Martian meteorite. The findings appear in the January 3, 2013 issue of the Science Express.
“This meteorite is unlike anything I’ve ever seen before,” Dr Agee said. “It’s a completely new type of Martian meteorite. It has everything in its composition that you’d want in order to further our understanding of the Red Planet. This unique Martian meteorite tells us what volcanism was like 2 billion years ago, but it also gives us a glimpse of ancient surface and environmental conditions on Mars that no other meteorite has offered.”
“This meteorite, made of brecciated volcanic rock, is consistent with the composition of surface rocks on Mars analyzed by Martian rovers and orbiters,” Dr Agee explained. “But, our analysis of the oxygen isotopes, oxygen atoms with different numbers of neutrons, shows that NWA 7034 is not like any other meteorites or planetary samples. The chemistry is consistent with surface rocks that have interacted with the Martian atmosphere, an idea that had been hypothesized by earlier studies. The abundance of water, some 6,000 parts per million, suggests that the meteorite interacted with Martian surface- or ground-water 2.1 billion years ago.”
The unique meteorite has some similarities to, but is very different from other Martian meteorites known as SNC (for three members of the group: Shergotty, Nakhla and Chassigny). SNC meteorites currently number 110. So far, they are the only meteoritic samples from Mars that scientists have been able to study in Earth-based laboratories. However, their point of origin on the Red Planet is uncertain. In fact, recent data from lander and orbiter missions suggest that they are a mismatch for the Martian crust.
“The texture of the NWA meteorite is not like any of the SNC meteorites,” explained co-author Dr Andrew Steele of the Carnegie Institution’s Geophysical Laboratory.
“It is made of cemented fragments of basalt, rock that forms from rapidly cooled lava, dominated with feldspar and pyroxene, most likely from volcanic activity. This composition is common for lunar samples, but not from other Martian meteorites.”
“Perhaps most exciting, is that the high water content could mean there was an interaction of the rocks with surface water either from volcanic magma, or from fluids from impacting comets during that time,” Dr Steele said. “It is the richest Martian meteorite geochemically and further analyses are bound to unleash more surprises.”
Bibliographic information: Agee CB et al. Unique Meteorite from Early Amazonian Mars: Water-Rich Basaltic Breccia Northwest Africa 7034. Science, published online January 3, 2013; doi: 10.1126/science.1228858