The Rosetta spacecraft is now in the immediate vicinity of the comet nucleus to be explored, the one of Comet 67P/Churyumov-Gerasimenko. This target will soon be mapped systematically, in great detail, as part of the preparations for the touchdown of the Philae lander, foreseen for November this year. However, the OSIRIS cameras have already delivered quite astounding pictures of the weird object, and we are as yet far from understanding exactly what we are looking at. Here are some examples of the riddles that have been posed and the scientists of the camera team are working on.

The discovery of the IBEX Ribbon, which is an area on the sky of enhanced emission of hydrogen atom flux, was a surprising finding of the Interstellar Boundary Explorer mission. The origin of the Ribbon is yet unknown and there are several competing hypotheses on Ribbon’s sources. According to one of them, the Ribbon forms in the Local Interstellar Cloud near the heliospheric boundary due to interaction of solar wind neutral particles with interstellar matter. According to another hypothesis, proposed by a team of researchers from CBK PAN led by Professor Stanisław Grzędzielski and published in 2010 in The Astrophysical Journal Letters, the Ribbon is a result of interaction between the Local Interstellar Cloud boundary and the Local Bubble. That happens much farther away from the Sun than in the first case. Those two totally different hypotheses explain the formation of similar energetic hydrogen atom fluxes, making it difficult to eliminate one of them on the basis of existing energetic hydrogen atoms measurements. To solve this dilemma, CBK PAN researchers have recently proposed to use observation of energetic helium atoms.