A Sinking Explanation from Rosetta
July 1st, 2015, 6:08PMRosetta scientists have new insight to the inner workings of comets. When the ESA spacecraft reached Comet 67P/Churyumov-Gerasimenko last fall, the mission team noticed several nearly perfectly circular pits. Now they believe they are sinkholes, created when ice sublimates underneath the surface and, eventually, the surface material collapses. Scientists at first thought the pits were from explosive outbursts, but they were able to observe such an outburst in April 2014, and it didn’t create the kind of pit they see elsewhere. The comet should get increasingly interesting as it reaches perihelion on August 13; Rosetta’s mission was recently extended through September 2016.