When Comet Churyumov-Gerasimenko, which was monitored by the European Rosetta spacecraft, approached its most active period last year, spotted ice composed of carbon dioxide was discovered on its surface. This event shook the scientists of the mission, since no one had ever observed this on comets – the study was published in the journal Science.
It turned out that the layer of carbon dioxide ice was located in an area comparable to the size of a football field, while the two patches of water ice were each larger than an Olympic pool and much larger than any previously observed patches of water ice on comets. Three layers of ice were found in the same area, in the comet's southern hemisphere.
The researchers also found that the combination of the complex shape of the Churyumov-Gerasimenko comet, its elongated path around the Sun and the significant inclination of its rotation contribute to the uneven distribution of the seasons between its two hemispheres. When Rosetta first arrived in orbit on the comet in August 2014, the northern hemisphere was still having a 5.5-year summer, and the southern hemisphere, most of which was dark, was winter.
However, shortly before the comet's approach to the Sun, in August 2015, the seasons changed, and a short but intense summer began in the southern hemisphere.
In the first half of 2015, the comet gradually became more active – active emissions of water vapor and other gases from the core of the cosmic body were observed. These processes lifted the dust cover from the comet's surface and allowed for an even better study of the geological feature of 67P.
The Rosetta mission was completed on September 30, 2016, when the spacecraft made a controlled hard landing on the comet's surface. ESA scientists consider their mission to be successful and are proud of the results.
