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Mars may have once had a continental crust

Scientists say the Red Planet's higher elevation southern hemisphere more and more recalls the continental crust of an early Earth.

By Brooks Hays
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Mars may have once had a continental crust
A clast of igneous embedded in a conglomerate rock in Gale crater reveals streaks of light-toned feldspar crystals. Photo by NASA/JPL

LOS ALAMOS, N.M., July 14 (UPI) -- A team of researchers, including scientists in France and the United States, say new data beamed by back Mars rover Curiosity suggests the Red Planet once possessed a continental crust.

In a new paper, published this week in the journal Nature Geoscience, scientists describe 20 rocks recently analyzed by Curiosity. The rocks, which researchers expected to reveal large samples of basalt, are mostly rich in silica, suggesting a different geological history than ones previously ascribed to Mars -- one more like Earth's.

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The newly studied rocks, sourced from inside Gale Crater, feature varying concentrations of alkaline compositions -- some with fine-grained and porphyritic textures, others with larger fragments of quartz diorite and granodiorite. The rocks are 3.6 billion years old.

"Along the rover's path we have seen some beautiful rocks with large, bright crystals, quite unexpected on Mars" Roger Wiens, a researcher at the Los Alamos National Laboratory, said in a press release. Wiens is the lead scientist on the team dedicated to Curiosity's ChemCam instrument.

"As a general rule, light-colored crystals are lower density, and these are abundant in igneous rocks that make up the Earth's continents," Wiens added.

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Most scientists believed Mars to be without magmatic activity, which is why researchers expected to find large expanses of basalt, as is found on Earth's ocean floors. But the silica-rich rocks suggests a more dynamic geologic and magmatic history that includes a crust and even plate tectonics.

"We conclude that silica-rich magmatic rocks may constitute a significant fraction of ancient Martian crust and may be analogous to the earliest continental crust on Earth," scientists wrote in their paper.

Scientists say they haven't found direct evidence of shifting plates on Mars, but that the Red Planet's higher elevation southern hemisphere more and more recalls the continental crust of an early Earth.

"There's a bit of evidence for the precursor to tectonics, because there are magnetic domains that were found in parts of the southern hemisphere on the surface of Mars," Wiens told Australia's ABC Science. "The planet doesn't have a magnetic field now, but it suggests that it did have one in the past."

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