This article is mirrored from the main ESA Web Portal.
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.
A combination of the complex shape of the comet, its elongated path around the Sun and the substantial tilt of its spin, seasons are spread unequally between the two hemispheres of the double-lobed Comet 67P/Churyumov–Gerasimenko.
When Rosetta arrived in August 2014, the northern hemisphere was still undergoing its 5.5 year summer, while the southern hemisphere was in winter and much of it was shrouded in darkness.
However, shortly before the comet’s closest approach to the Sun in August 2015, the seasons changed and the southern hemisphere experienced a brief but intense summer, exposing this region ...