On the origin of O${}_2$ and other volatile species in comets

Abstract

Molecular oxygen, O${}_2$, was recently detected in comet 67P by the ROSINA instrument on board the Rosetta spacecraft with a surprisingly high abundance of 4 % relative to H${}_2$O, making O${}_2$ the fourth most abundant in comet 67P. Other volatile species with similar volatility, such as molecular nitrogen N${}_2$, were also detected by Rosetta, but with much lower abundances and much weaker correlations with water. Here, we investigate the chemical and physical origin of O${}_2$ and other volatile species using the new constraints provided by Rosetta. We follow the chemical evolution during star formation with state-of-the-art astrochemical models applied to dynamical physical models by considering three origins: i) in dark clouds, ii) during forming protostellar disks, and iii) during luminosity outbursts in disks. The models presented here favour a dark cloud (or "primordial") grain surface chemistry origin for volatile species in comets, albeit for dark clouds which are slightly warmer and denser than those usually considered as solar system progenitors.

To appear in "Astrochemistry VII -- Through the Cosmos from Galaxies to Planets", proceedings of the IAU Symposium No. 332, 2017, Puerto Varas, Chile. M. Cunningham, T. Millar and Y. Aikawa, eds. (9 pages, 2 figures)

References in corpus (9)

• Polycylcic Aromatic Hydrocarbons (PAH's) in dense cloud chemistry
• The ancient heritage of water ice in the solar system
• Laboratory evidence for efficient water formation in interstellar ices
• Variable protostellar accretion with episodic bursts
• Formation of hydrogen peroxide and water from the reaction of cold hydrogen atoms with solid oxygen at 10K
• Multilayer formation and evaporation of deuterated ices in prestellar and protostellar cores
• CO and N${}_2$ desorption energies from water ice
• Methanol Along the Path from Envelope to Protoplanetary Disc
• Molecular Oxygen in Oort Cloud Comet 1P/Halley