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Sunlight Can Crack Rocks on Asteroids

14 Jul 2020, 19:45 UTC
Sunlight Can Crack Rocks on Asteroids
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This image shows a group of large boulders located just north of asteroid Bennu’s equatorial region. Two of the boulders have flat faces that exhibit linear marks. The boulder in the lower right shows evidence of exfoliation, where thermal fracturing likely caused small, thin layers to flake off of the boulder’s surface. The image was taken by the PolyCam camera on NASA’s OSIRIS-REx spacecraft on July 20, from a distance of 0.4 miles (0.7 km). Credit: NASA / Goddard / University of Arizona
Here on Earth the surfaces of pretty much all but the most freshly-exposed (geologically-speaking, of course) rock surfaces exhibit the effects of atmospheric weathering—from rain, snow, and ice to wind, dust-blown sand, flowing water, and extreme heat. And underlying all of that are the relentless forces of tectonic activity. But on dry, airless, and tectonically “dead” worlds in space like asteroids and many moons, rocky surfaces weather differently and much, much more slowly. The only rain comes in the form of occasional microscopic meteorite strikes and the only wind is charged atomic particles streaming out from the Sun into the vacuum of space. Both are incessant but their effects are, even on Earthly geologic time scales, extremely ...

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