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Curiosity rover finds Earth-like ‘Continental Crust’ on Mars

July 13, 2015 Igneous clast named Harrison embedded in a conglomerate rock in Gale crater, Mars, shows elongated light-toned feldspar crystals. The mosaic merges an image from Mastcam with higher-resolution images from ChemCam’s Remote Micro-Imager. Credit: NASA/JPL-Caltech/LANL/IRAP/U. Nantes/IAS/MSSS. Igneous clast named Harrison embedded in a conglomerate rock in Gale crater, Mars, shows elongated light-toned feldspar crystals. The mosaic merges an image from Mastcam with higher-resolution images from ChemCam’s Remote Micro-Imager. Credit: NASA/JPL-Caltech/LANL/IRAP/U. Nantes/IAS/MSSS.

July 13, 2015
Igneous clast named Harrison embedded in a conglomerate rock in Gale crater, Mars, shows elongated light-toned feldspar crystals. The mosaic merges an image from Mastcam with higher-resolution images from ChemCam’s Remote Micro-Imager. Credit: NASA/JPL-Caltech/LANL/IRAP/U. Nantes/IAS/MSSS.

NASA’s Curiosity rover found Earth-like rocks on Mars for the first time showing granitic continental crust.

The ChemCam laser instrument on NASA’s Curiosity rover found it when it turned the beam onto some unusually light-colored rocks on Mars.

“Along the rover’s path we have seen some beautiful rocks with large, bright crystals, quite unexpected on Mars” said Roger Wiens of Los Alamos National Laboratory. “As a general rule, light-colored crystals are lower density, and these are abundant in igneous rocks that make up the Earth’s continents.”

Mars is known to be an entirely basaltic planet, with igneous rocks that are dark and relatively dense, similar to those forming the Earth’s oceanic crust, Wiens said. But Gale crater, where the Curiosity rover landed, contains fragments of some ancient igneous rocks formed some 3.6 billion years ago, which are distinctly light in color.

Gale crater, excavated about 3.6 billion years ago into rocks of greater age, provided a window into the Red Planet’s primitive crust. The crater walls provided a natural geological cut-away view 1-2 miles down into the crust. Access to some of these rocks, strewn along the rover’s path, provided critical information that could not be observed by mere satellite orbits.

French and U.S. scientists observed images and chemical results of 22 of these rock fragments to determine that these pale rocks are rich in feldspar, possibly with some quartz, and they are unexpectedly similar to Earth’s granitic continental crust.

According to the paper’s first author, Violaine Sautter, these primitive Martian crustal components bear a strong resemblance to a terrestrial rock type known to geologists as TTG (Tonalite-Trondhjemite-Granodiorite), rocks that predominated in the terrestrial continental crust in the Archean era (more than 2.5 billion years ago).

The results were published in Nature Geoscience. ChemCam, a laser-induced breakdown spectrometer (LIBS) for chemical analysis gives a sub-millimeter scale, detailed images with its Remote Micro Imager.

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