Ammonium salts are a reservoir of nitrogen on a cometary nucleus and possibly on some asteroids

Olivier Poch (1) , Istiqomah Istiqomah (1) , Eric Quirico (1) , Pierre Beck (1) , Bernard Schmitt (1) , Patrice Theulé , Alexandre Faure (1) , Pierre Hily-Blant (1) , Lydie Bonal (1) , Andrea Raponi , Mauro Ciarniello , Batiste Rousseau , Sandra Potin , Olivier Brissaud (1) , Laurène Flandinet (1) , Gianrico Filacchione , Antoine Pommerol , Nicolas Thomas , David Kappel , Vito Mennella , Lyuba Moroz , Vassilissa Vinogradoff (2) , Gabriele Arnold , Stéphane Erard (3) , Dominique Bockelée-Morvan (3) , Cédric Leyrat (3) , Fabrizio Capaccioni (4) , Maria Cristina de Sanctis (4) , Andrea Longobardo , Francesca Mancarella , Ernesto Palomba , Federico Tosi

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
2 PIIM - Physique des interactions ioniques et moléculaires
3 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics
4 IAPS - Istituto di Astrofisica e Planetologia Spaziali - INAF

The measured nitrogen-to-carbon ratio in comets is lower than for the Sun, a discrepancy which could be alleviated if there is an unknown reservoir of nitrogen in comets. The nucleus of comet 67P/Churyumov-Gerasimenko exhibits an unidentified broad spectral reflectance feature around 3.2 micrometers, which is ubiquitous across its surface. On the basis of laboratory experiments, we attribute this absorption band to ammonium salts mixed with dust on the surface. The depth of the band indicates that semivolatile ammonium salts are a substantial reservoir of nitrogen in the comet, potentially dominating over refractory organic matter and more volatile species. Similar absorption features appear in the spectra of some asteroids, implying a compositional link between asteroids, comets, and the parent interstellar cloud.

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]

Olivier Poch, Istiqomah Istiqomah, Eric Quirico, Pierre Beck, Bernard Schmitt, et al.. Ammonium salts are a reservoir of nitrogen on a cometary nucleus and possibly on some asteroids. Science, 2020, 367 (6483), pp.eaaw7462. ⟨10.1126/science.aaw7462⟩. ⟨hal-02996633⟩