Distributed glycine in comet 67P/Churyumov-Gerasimenko

Abstract

Most of the gaseous molecules that are detected in cometary atmospheres are produced through sublimation of nucleus ices. Distributed sources may also occur, that is, production within the coma, from the solid component of dust particles that are ejected from the nucleus. Glycine, the simplest amino acid, was observed episodically in the atmosphere of comet 67P/Churyumov-Gerasimenko (67P) by the ROSINA mass spectrometer on board the Rosetta probe. A series of measurements on 28 March 2015 revealed a distributed density profile at between 14 and 26 km away from the nucleus. We here present and discuss three study cases: (i) glycine emitted directly and only from the nucleus, (ii) glycine emitted from the sublimation of solid-state glycine on the dust particles that are ejected from the nucleus, and (iii) glycine molecules embedded in water ice that are emitted from the sublimation of this ice from the dust particles that are ejected from the nucleus. A numerical model was developed to calculate the abundance of glycine in the atmosphere of comet 67P as a function of the distance from the nucleus, and to derive its initial abundance in the lifted dust particles. We show that a good fit to the observations corresponds to a distributed source of glycine that is embedded in sublimating water ice from dust particles that are ejected from the nucleus (iii). The few hundred ppb of glycine embedded in water ice on dust particles (nominally 170 ppb by mass) agree well with the observed distribution.

Molecular composition of comet 46P/Wirtanen from millimetre-wave spectroscopy

“…(i) Centre of the range proposed by Irvine et al (2000), which is estimated from the analogy between NS and NO and the fact that sulphur species have shorter lifetimes. ( j) Value used in Hadraoui et al (2019).…”

Insoluble organic matter in chondrites: Archetypal melanin-like PAH-based multifunctionality at the origin of life?

“…The smallest amino acid glycine was also detected in this comet [100], as well as in Wild-2 comet [101,102], with no larger amino acids indisputably being detected. The SOM content of Antarctic micrometeorites (AMMs) has also been analyzed, in particular for PAHs [103,104], and amino acids [105][106][107].…”

Organic Matter in Cometary Environments

“…The amino acid glycine was detected in samples returned from 81P by the Stardust mission [ 55 ]. Glycine was also detected around 67P by Rosetta [ 12 ], and further analysis showed that glycine had a distributed source, consistent with release from dust grains in the coma [ 122 ].…”