The July 20, 2015 photo released by the European Space Agency ESA on Tuesday, July 28, 2015 shows an image of the comet 67P/Churyumov-Gerasimenko with its coma taken by the Navcam camera of the Rosetta orbiter from a distance of 171km from the comet center. (AP Photo / ESA/Rosetta / Navcam)