Infrared detection of aliphatic organics on a cometary nucleus

Abstract

The European Space Agency's Rosetta mission<SUP>1</SUP> 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<SUP>2</SUP>, seems to be an assemblage of ices, minerals and organic material<SUP>3</SUP>. 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 µm absorption feature populated by fainter bands. Among these, we unambiguously identify the presence of aliphatic organics by their ubiquitous 3.38 µm, 3.42 µm and 3.47 µm 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<SUP>4</SUP>.