Infrared detection of aliphatic organics on a cometary nucleus

The European Space Agency's Rosetta mission(1) has acquired unprecedented measurements of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko (hereafter, 67P), the composition of which, as determined by in situ and remote-sensing instruments, including the VIRTIS instrument(2), seems to be an assemblage of ices, minerals and organic material(3). We performed a refined analysis of infrared observations of the nucleus of 67P carried out by the VIRTIS-M hyperspectral imager. We find that the overall shape of the infrared spectrum of 67P is similar to that of other carbon-rich outer Solar System objects, suggesting a possible genetic link with them. More importantly, we also confirm the complex spectral structure of the wide 2.8-3.6 mu m absorption feature populated by fainter bands. Among these, we unambiguously identify the presence of aliphatic organics by their ubiquitous 3.38 mu m, 3.42 mu m and 3.47 mu m bands. This infrared detection of aliphatic species on a cometary surface has strong implications for the evolutionary history of the primordial Solar System and is evidence that comets provide an evolutionary link between interstellar material and Solar System bodies(4). A refined analysis of infrared observations of comet 67P/Churyumov-Gerasimenko from the VIRTIS instrument on board the Rosetta spacecraft has revealed the presence of aliphatic organic molecules on the comet nucleus.