Evidence of ammonium salts in comet 67P as explanation for the nitrogen depletion in cometary comae

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Authors
Altwegg, K.
Balsiger, H.
Hänni, N.
Rubin, M.
Schuhmann, M.
Schroeder, I.
Sémon, T.
Wampfler, S.
Berthelier, J.-J.
Briois, C.
Combi, M.
Gombosi, T.I.
Cottin, H.
De Keyser, J.
Dhooghe, F.
Fiethe, B.
Fuselier, S.A.
Discipline
Physical sciences
Subject
Astronomy and planetary science
Planetary science
Space physics
Audience
Scientific
Date
2020Metadata
Show full item recordDescription
Cometary comae are generally depleted in nitrogen. The main carriers for volatile nitrogen in comets are NH3 and HCN. It is known that ammonia readily combines with many acids, such as HCN, HNCO and HCOOH, encountered in the interstellar medium as well as in cometary ice to form ammonium salts (NH4+X−) at low temperatures. Ammonium salts, which can have a substantial role in prebiotic chemistry, are hard to detect in space as they are unstable in the gas phase and their infrared signature is often hidden by thermal radiation or by, for example, OH in minerals. Here we report the presence of all possible sublimation products of five different ammonium salts in the comet 67P/Churyumov–Gerasimenko measured by the ROSINA instrument onboard Rosetta. The relatively high sublimation temperatures of the salts leads to an apparent lack of volatile nitrogen in the coma. This then also explains the observed trend of higher NH3/H2O ratios with decreasing perihelion distances in comets.
Citation
Altwegg, K.; Balsiger, H.; Hänni, N.; Rubin, M.; Schuhmann, M.; Schroeder, I.; Sémon, T.; Wampfler, S.; Berthelier, J.-J.; Briois, C.; Combi, M.; Gombosi, T.I.; Cottin, H.; De Keyser, J.; Dhooghe, F.; Fiethe, B.; Fuselier, S.A. (2020). Evidence of ammonium salts in comet 67P as explanation for the nitrogen depletion in cometary comae. , Nature Astronomy, Vol. 4, Issue 5, DOI: 10.1038/s41550-019-0991-9.Identifiers
Type
Article
Peer-Review
Yes
Language
eng