Desert meteorite shows signs of wetter Mars

Posted by Kate Taylor

A meteorite found in the Moroccan desert in 2011 appears to have originated in Mars' crust - and contains much more water than any Martian meteorite ever found before.

It's also the only meteorite found to date to 2.1 billion years ago, the early era of the most recent geologic epoch on Mars, known as the Amazonian.

Dubbed Northwest Africa (NWA) 7034, has some notable differences from the 110 previously-studied Martian meteorites known as SNC. No-one knows where on Mars these originated, although recent data indicates it wasn't the crust.

"The texture of the NWA meteorite is not like any of the SNC meteorites. 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," says Andrew Steele, who led the carbon analysis at the Carnegie Institution's Geophysical Laboratory.

"This unusual meteorite's chemistry suggests it came from the Martian crust. It is the first link thus far of any meteorite to the crust. Our carbon analysis also showed the presence of macromolecular organic carbon in feldspar grains associated with iron oxides, hinting that perhaps there is a different non-biological process at work than that explaining the presence of macromolecular carbon in other Martian meteorites."

The basaltic rock in the meteorite was found to be consistent with what Martian rovers and orbiters have discovered about the crust or upper mantle of Mars. An analysis of the oxygen isotopes showed a chemistry is consistent with a surface origin and an interaction with the Martian atmosphere.

And the abundance of water, at around 6000 parts per million, suggests that the meteorite interacted with the Martian surface about 2.1 billion years ago.

"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," says Steele. "It is the richest Martian meteorite geochemically, and further analyses are bound to unleash more surprises."