On the attempts to measure water (and other volatiles) directly at the surface of a comet

Abstract

The Ptolemy instrument on the Philae lander (of the Rosetta space mission) was able to make measurements of the major volatiles, water, carbon monoxide and carbon dioxide, directly at the surface of comet 67P/Churyumov–Gerasimenko. We give some background to the mission and highlight those instruments that have already given insights into the notion of water in comets, and which will continue to do so as more results are either acquired or more fully interpreted. On the basis of our results, we show how comets may in fact be heterogeneous over their surface, and how surface measurements can be used in a quest to comprehend the daily cycles of processes that affect the evolution of comets. This article is part of the themed issue ‘The origin, history and role of water in the evolution of the inner Solar System’.

The origin, history and role of water in the evolution of the inner Solar System

“…The Rosetta mission approached the nucleus of the comet 67P/Churyumov-Gerasimenko and delivered the Philae lander to the surface in 2014 [11]. This mission showed that comets are highly heterogeneous in their composition, resulting from their diurnal cycles [12]. Although having planets pelted with cometary snowballs is an appealing model to deliver volatiles, the C, N and O isotopic evidence rule out most comets as the source of most inner Solar System water.…”