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Rosetta’s comet approached its most active period last year, the spacecraft spotted carbon dioxide ice – never before seen on a comet – followed by the emergence of two unusually large patches of water ice.
The carbon dioxide ice layer covered an area comparable to the size of a football pitch, while the two water ice patches were each larger than an Olympic swimming pool and much larger than any signs of water ice previously spotted at the comet.
The three icy layers were all found in the same region, on the comet’s southern hemisphere.
Sequence of 23 images of Comet 67P/Churyumov–Gerasimenko taken with Rosetta’s OSIRIS narrow-angle camera on 4 July 2015, about a month before the comet’s closest approach to the Sun. The three-colour images are made from observations at 480, 649 and 882 nm. The images are taken at 30 minute intervals and span a full day at the comet, which spins around its axis in about 12.4 hours. The Sun is towards the top of the frame. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; Reprinted with permission from S. Fornasier et al., Science 10.1126/science.aag2671 (2016)
A combination of ...