ESA’s Rosetta spacecraft has been able to survey the dark and cold regions of the Churyumov-Gerasimenko/ Comet 67P for the first time, revealing new data on their composition.
Since the spacecraft reached Comet 67P, all instruments aboard have been collecting data on the environment and surface of the oddly shaped comet.
It is particularly the odd shape, combined with Comet 67P’s orbiting pattern that until recently kept Rosetta from accessing one of the key regions of the comet’s surface, one portion of the nucleus, close to the south pole.
Comet 67P completes one orbit in 6.5 years. Taking into account its double-lobe formation and the angle of inclination of the comet’s rotation axis, the seasons experienced by the two hemispheres are certainly peculiar. The northern hemisphere is exposed to a 5.5-year-long summer, while the southern hemisphere experiences a long, cold winter, away from sunlight. As Comet 67P reaches the closest point in its orbit to the Sun, the southern hemisphere finally gets the chance to experience a short summer.
At the time when Rosetta reached Comet 67P, the northern hemisphere was still experiencing summer, while the southern hemisphere had been experiencing winter for approximately five years.
It was too soon to tell, but scientists were wondering what was happening in the dark, inaccessible regions that neither of the instruments Rosetta is equipped with could survey. The only instruments that could collect some data in the southern hemisphere was the Microwave Instrument for Rosetta Orbiter (MIRO). The Visible, InfraRed and Thermal Imaging Spectrometer (VIRTIS), or Rosetta’s Optical, Spectroscopic and Infrared Remote Imaging System (OSIRIS) couldn’t catch a glimpse.
As such, the new paper published in the Astronomy and Astrophysics journal reveals data that MIRO gathered from August to October 2014 on Comet 67P’s southern hemisphere.
Mathieu Choukroun with NASA’s Jet Propulsion Laboratory, Pasadena, California:
“We observed the ‘dark side’ of the comet with MIRO on many occasions after Rosetta’s arrival at Comet 67P, and these unique data are telling us something very intriguing about the material just below its surface”.
The intriguing details refer to the possible presence of ice just a foot under the surface of these previously uncharted regions. However, the surface doesn’t present the same composition. According to the scientific team, one possible explanation might be the seasonal cycle experience by the comet’s two hemispheres. As the comet was reaching the previous perihelion, gases and water transpired on the southern hemisphere. As it entered winter once more and the temperature dropped significantly, the water condensed, thus bringing the icy patches in the subsurface.
More research is needed according to the scientists who say these are just preliminary results. At the time when the data was gathered, not much was known of the nucleus of Comet 67P or the mostly dark and cold polar region.
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