The Rosetta spacecraft has been studying the envrionment and surface of the comet 67P/Churyumov-Gerasimenko since its arrival. However, thanks to the combination of its double-lobed shape and the inclination of its rotation axis, large parts of the comet's south pole have remained inaccessible. Adding to the peculiarity of the situation was the fact that the comet exhibits a peculiar seasonal pattern during its six-and-a-half year orbit. The northern hemisphere experiences a five-and-a-half year long summer, with the southern hemisphere receiving the sun's light and warmth for only about 12 months.
When Rosetta arrived at 67P/C-G in August 2014, the comet was still experiencing its long summer in the northern hemisphere. As a result, no instruments could be used to collect data from the dark south, with the exception of the Microwave Instrument for Rosetta Orbiter (MIRO).
"We observed the 'dark side' of the comet with MIRO on many occasions after Rosetta's arrival at 67P/C-G, and these unique data are telling us something very intriguing about the material just below its surface," said Mathieu Choukroun from NASA's Jet Propulsion Laboratory (JPL), Pasadena, California, lead author of a study based on these reports, which has been accepted for publication in the journal Astronomy and Astrophysics, reported NASA.
The brief, hot southern summer began on 67P/C-G in May 2015, which will last until early 2016. It has now become possible to observe the southern parts of the comet using the other instruments available on Rosetta.
"In the past few months, Rosetta has flown over the southern polar regions on several occasions, starting to collect data from this part of the comet after summer began there. At the beginning of the southern summer, we had a paucity of observations in these regions as Rosetta's trajectory focused on the northern hemisphere due to ongoing communication with the lander, Philae. However, closer to perihelion we were able to begin observing the south," ESA Rosetta project scientist Matt Taylor said, according to Gizmag.
"First, we observed these dark regions with MIRO, the only instrument able to do so at the time, and we tried to interpret these unique data. Now, as these regions became warmer and brighter around perihelion, we can observe them with other instruments, too," Taylor, added, according to Astronomy Magazine.
Rosetta's mission is to study the environment of the comet, and it is currently about 930 miles (1,500 kilometers) from the nucleus.
"We hope that, by combining data from all these instruments, we will be able to confirm whether or not the south pole had a different composition and whether or not it is changing seasonally," said Mark Hofstadter, MIRO principal investigator at JPL.
