Mars rover Curiosity finds evidence of planet’s primitive continental crust

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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.

Mars Curiosity is busy with its digging operations, all the while keeping a close eye on the sunspots, and its latest observations through its ChemCam laser instrument has revealed presence of what looks like Mars’ primitive continental crust.

These unusually light-colored rocks on Mars are seemingly similar to granitic continental crust rocks found on Earth.

Though Mars, as a whole, is mostly viewed as a planet packing basaltic rocks including igneous rocks that are dark and relatively dense, similar to those forming the Earth’s oceanic crust, there have been instances where certain parts contain fragments of very ancient igneous rocks (around 4 billion years old) that are distinctly light in color, and which were analyzed by the ChemCam instrument on Curiosity.

Based on the images and chemical analysis of the rock fragments, scientists say that these pale rocks are rich in feldspar, possibly with some quartz, and they are unexpectedly similar to Earth’s granitic continental crust.

The findings have been published in journal Nature Geoscience and paper’s first author, Violaine Sautter, explains that 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).

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 other means, such as by orbiting satellites.

ChemCam, a laser-induced breakdown spectrometer (LIBS), provides chemical analyses at a sub-millimeter scale; detailed images were provided by its Remote Micro Imager.