Infrared Detection Of Aliphatic Organics On A Cometary Nucleus

Comparison between 67P spectrum and other bodies of the solar system normalized at 2.3 µm. Arbitrary offsets were applied to the spectra, except for 67P. The absorption features centered at 3.1 µm and 3.3 - 3.4 µm are not only observed on comet 67P but also on several asteroids: (361) Bononia30 , (52) Europa30 , (24) Themis28 , (65) Cybele29, and Jupiter Trojans (average spectrum of six from the “less-red” group)26 . Himalia (not shown here) is an irregular satellite of Jupiter having a strikingly similar spectrum as (52) Europa, as shown in Brown & Rhoden31. Trojans and average D-type asteroids32 (such as Bononia) show a similar red spectral slope with respect to that of comet 67P.

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.

A. Raponi, M. Ciarniello, F. Capaccioni, V. Mennella, G. Filacchione, V. Vinogradoff, O. Poch, P. Beck, E. Quirico, M. C. De Sanctis, L. Moroz, D. Kappel, S. Erard, D. Bockelée-Morvan, A. Longobardo, F. Tosi, E. Palomba, J.-P. Combe, B. Rousseau, G. Arnold, R. W. Carlson, A. Pommerol, C. Pilorget, S. Fornasier, G. Bellucci, A. Barucci, F. Mancarella, M. Formisan, G. Rinaldi, I. Istiqomah, C. Leyrat

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
DOI: 10.1038/s41550-019-0992-8
Cite as: arXiv:2009.14476 [astro-ph.EP] (or arXiv:2009.14476v1 [astro-ph.EP] for this version)
Submission history
From: Pierre Beck
[v1] Wed, 30 Sep 2020 07:23:50 UTC (1,249 KB)
Astorochemistry, Astrobiology,

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