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How Bizarre

Mysterious circles appear, grow on comet

Rosetta spacecraft spotted five round depressions in June, early July

By
8:00am, September 28, 2015
comet circles

SEE SPOT GROW  The first of five growing circles on comet 67P appears in a June 5 image from Rosetta (left). By June 23, two spots were spreading across the surface (center). They were joined by a third on July 2 (right).

A comet is growing its own version of crop circles. Over the course of a month, five expanding disklike depressions appeared on the surface of 67P/Churyumov-Gerasimenko in images taken by the Rosetta spacecraft, which has been orbiting 67P since August 2014 (SN: 9/6/14, p. 8).

The first roundish feature showed up on June 3 and was joined by a second 10 days later. Within a month, the first spot had grown to 220 meters across and 5 meters deep, and it had run into its neighbor. Three more spots appeared in early July, flanking the original two, researchers report online September 15 in Astronomy & Astrophysics.

The spots form around weak points in the surface, where

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