A comparison between the two lobes of comet 67P/Churyumov-Gerasimenko based on D/H ratios in H2O measured with the Rosetta/ROSINA DFMS

TL;DR

This study compares the D/H ratios in water from the two lobes of comet 67P/Churyumov-Gerasimenko using Rosetta data, finding no significant difference and suggesting a common formation region.

Contribution

It provides the first in situ comparison of D/H ratios in the two lobes of 67P, indicating their compositional homogeneity.

Findings

No appreciable difference in D/H ratios between lobes

Both lobes likely formed in the same region

Supports homogeneous composition hypothesis

Abstract

The nucleus of the Jupiter-family comet 67P/Churyumov-Gerasimenko was discovered to be bi-lobate in shape when the European Space Agency spacecraft Rosetta first approached it in July 2014. The bi-lobate structure of the cometary nucleus has led to much discussion regarding the possible manner of its formation and on how the composition of each lobe might compare with that of the other. During its two-year-long mission from 2014 to 2016, Rosetta remained in close proximity to 67P/Churyumov-Gerasimenko, studying its coma and nucleus in situ. Based on lobe-specific measurements of HDO and H2O performed with the ROSINA DFMS mass spectrometer on board Rosetta, the Deuterium-to-Hydrogen ratios in water from the two lobes could be compared. No appreciable difference was observed, suggesting that both lobes formed in the same region and are homogeneous in their Deuterium-to-Hydrogen ratios.