The presence of clathrates in comet 67P/Churyumov-Gerasimenko

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Why is it important?

For decades, scientists have agreed that comets are mostly water ice, but what kind of ice — amorphous or crystalline — is still up for debate. The structure and phase of the ice is important because it tells us about how and where in the solar nebula the comet may have formed. We show based on in situ Rosetta data that comet 67P contains a crystalline form of water ice called clathrates. If the presence of clathrates in the nucleus means that the building blocks of 67P were themselves made out of crystalline ices and clathrates instead of amorphous ice, then 67P likely formed closer to the Sun than previously considered for Jupiter Family Comets.