Amazing pictures taken with the spacecraft “Rosetta” (Rosetta), demonstrate the presence of geological forms, like dunes on the surface of comet Churyumov-Gerasimenko. Scientists from the laboratory Laboratoire de Physique et Mécanique des Milieux Hétérogènes (CNRS/ESPCI Paris/UPMC/Université Paris Diderot), analysed available images and made the modeling of the emission from the surface of a comet to explain the observed phenomena. Researchers have shown that a large difference in gas pressures between the illuminated and dark solar rays by the parties of the comet leads to the formation of winds that can carry dust particles and form dunes.
Formation of dunes requires the presence of strong winds that are characteristic of a rather thick atmosphere of the Earth, but almost absent in the rarefied atmospheres of a large number of space bodies, including comets. However, pictures taken using the apparatus “Rosetta”, found that the surface of comet 67P/Churyumov-Gerasimenko have dunes with a height of about 10 meters, which also move along the surface of this night visitor from outer space.
In an attempt to explain these puzzling observations, a group of researchers headed by Jia Pan (Pan Jia) found that dunes move across the surface of the comet under the action of winds. The occurrence of these winds is due to the motion of gas masses thin (with a pressure of several Pascals) of the atmosphere, emerging on the Sunny side of the comet, which under the action of pressure difference move in the direction of the night side of the comet. Because gravity on the comet is extremely weak, the power flow of these winds is enough to transport the particles of material with dimensions of a few centimeters.