  The ESA Rosetta mission has acquired unprecedented measurements of comet
67/P-Churyumov-Gerasimenko (hereafter 67P) nucleus surface, whose composition,
as determined by in situ and remote sensing instruments including VIRTIS
(Visible, InfraRed and Thermal Imaging Spectrometer) appears to be made by an
assemblage of ices, minerals, and organic material. We performed a refined
analysis of infrared observations of the nucleus of comet 67P carried out by
the VIRTIS-M hyperspectral imager. We found that the overall shape of the 67P
infrared spectrum is similar to that of other carbon-rich outer solar system
objects suggesting a possible genetic link with them. More importantly, we are
also able to confirm the complex spectral structure of the wide 2.8-3.6 micron
absorption feature populated by fainter bands. Among these, we unambiguously
identified the presence of aliphatic organics by their ubiquitous 3.38, 3.42
and 3.47 micron bands. This novel infrared detection of aliphatic species on a
cometary surface has strong implications for the evolutionary history of the
primordial solar system and give evidence that comets provide an evolutionary
link between interstellar material and solar system bodies.
