Elemental and molecular abundances in comet 67P/Churyumov-Gerasimenko

TL;DR

This study analyzes the elemental and molecular composition of comet 67P/Churyumov-Gerasimenko using in-situ measurements from the Rosetta mission, revealing its near-solar elemental abundances and supporting its pristine nature.

Contribution

It provides an integrated inventory of major volatile elements in comet 67P/Churyumov-Gerasimenko based on in-situ and literature data, highlighting its primitive composition.

Findings

Near-solar abundances of oxygen and carbon

Depletion of hydrogen and nitrogen compared to solar

Lower devolatilization than inner solar system objects

Abstract

Comets are considered to be some of the most pristine and unprocessed solar system objects accessible to in-situ exploration. Investigating their molecular and elemental composition takes us on a journey back to the early period of our solar system and possibly even further. In this work, we deduce the bulk abundances of the major volatile species in comet 67P/Churyumov-Gerasimenko, the target of the European Space Agency's Rosetta mission. The basis are measurements obtained with the ROSINA instrument suite on board the Rosetta orbiter during a suitable period of high outgassing near perihelion. The results are combined with both gas and dust composition measurements published in the literature. This provides an integrated inventory of the major elements present in the nucleus of 67P/Churyumov-Gerasimenko. Similar to comet 1P/Halley, which was visited by ESA's Giotto spacecraft in 1986, comet 67P/Churyumov-Gerasimenko also shows near-solar abundances of oxygen and carbon, whereas hydrogen and nitrogen are depleted compared to solar. Still, the degree of devolatilization is lower than that of inner solar system objects, including meteorites and the Earth. This supports the idea that comets are among the most pristine objects in our solar system.