LONDON: Using the Microwave Instrument for the Rosetta Orbiter (MIRO), scientists have studied the comet’s southern polar regions at the end of their long winter season. The data suggest that these dark, cold regions host ice within the first few tens of centimetres below the surface in much larger amounts than elsewhere on the comet.
Since its arrival at Comet 67P/Churyumov-Gerasimenko, Rosetta has been surveying the surface and the environment of this curiously-shaped body. But for a long time, a portion of the nucleus – the dark, cold regions around the comet’s south pole – remained inaccessible to almost all instruments on the spacecraft.
Due to a combination of its double-lobed shape and the inclination of its rotation axis, Rosetta’s comet has a very peculiar seasonal pattern over its 6.5 year-long orbit. Seasons are distributed very unevenly between the two hemispheres, each of which comprises parts of both comet lobes and of the ‘neck’.
For most of the comet’s orbit, the northern hemisphere experiences a very long summer, lasting over 5.5 years, and the southern hemisphere undergoes a long, dark and cold winter. However, a few months before the comet reaches perihelion – the closest point to the Sun along its orbit – the situation changes, and the southern hemisphere transitions to a brief and very hot summer.
When Rosetta arrived at 67P/C-G in August 2014, the comet was still experiencing its long summer in the northern hemisphere and regions on the southern hemisphere received very little sunlight. Moreover, a large part of this hemisphere, close to the comet’s south pole, was in polar night and had been in total darkness for almost five years.
