ESA’s Rosetta space probe is continuing its approach to the comet 67P/Churyumov-Gerasimenko and the photos that are coming are more and more decomaed. In July, the images of the comet’s nucleus had revealed its binary nature, now scientists but also merely curious people can see it in a much better quality. Its coma begins to show an interesting activity too and Rosetta has provided more surprising data.
These days, the comet 67P/Churyumov-Gerasimenko is between the orbits of Jupiter and Mars, at a distance which is still more than 500 million km (about 310 million miles) from the Sun. It will take a little more than a year to reach its perihelion, which is the point of closest approach to the Sun, estimated at about 185 million km (about 115 million miles), between the orbits of Mars and Earth.
The Rosetta spacecraft is studying both the nucleus of the comet 67P/Churyumov-Gerasimenko and the activity of its coma, which will grow as it approaches the Sun. In particular the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System ) camera, with its narrow angle lens and its wide angle lens, is at this moment taking very interesting pictures.
The coma of 67P/Churyumov-Gerasimenko is currently asymmetric. This is due to the irregular shape of its nucleus but also the activity that is distributed unevenly on the comet’s surface. The nucleus rotates on itself so different parts are illuminated by sunlight and, depending on their composition, their ice contents sublimate at different speeds.
When the very irregular shape of the nucleus of the comet 67P/Churyumov-Gerasimenko was identified, it seemed obvious that it was a binary formation created by two objects that merged. However, someone else has suggested that actually it’s a single nucleus that for some reason was eroded in such a way as to give it that peculiar shape.
The “neck” connecting the two segments of the nucleus is the area where there are more clues about the history of the comet 67P/Churyumov-Gerasimenko. A part of this neck seems much brighter than the surrounding regions. This may be due to a different composition of its surface or in the different size of the dust grains that cover it. One area where the ice is directly exposed could be brilliant but it’s just one of the possibilities.
The images, even the last one taken on July 29, 2014 from a distance of about (1950 km about 1210 miles) from the comet that reveal a lot more details are still too limited to give answers. It’s for this reason that the Rosetta space probe has various spectroscopes and other instruments in addition to the Philae lander that will land on the nucleus.
Over the past few weeks, the VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) spectrometer was still able to measure the temperature of the surface of the comet 67P/Churyumov-Gerasimenko. The average was -70°C (-94° Fahrenheit), which may seem really low but is 20-30°C higher than expected. This suggests that it’s covered with dark and dusty materials that absorb a bit of sunlight.
Again, the Rosetta space probe can better study the surface of the comet 67P/Churyumov-Gerasimenko when it gets close to it. At that point, it can use VIRTIS to create a map of the daily variations of the surface temperature of the different parts of the comet to understand their characteristics.
There are only a few days left before the Rosetta space probe reaches the comet 67P/Churyumov-Gerasimenko. The recent discoveries are making its mission more and more interesting and probably the best is yet to come.