A special issue of the journal “Science” describes an early analysis of data collected by the lander Philae in its descent to the surface of the comet 67P/Churyumov-Gerasimenko. Its mission was short and ESA engineers can’t get a stable contact after those of recent weeks but the data collected were very helpful. Another very interesting study just appeared about the interaction of the comet with the solar wind.
The Philae lander’s descent on the surface of the comet 67P/Churyumov-Gerasimenko on November 12, 2014 was exciting. Unfortunately some surprises were negative, in particular the nature of the surface. ESA scientists expected a soft surface Philae could anchor to, instead the soft layer was probably thin and the lander bounced.
The photographs taken by the Philae lander’s ROLIS (Rosetta Lander Imaging System) instrument shows a granular surface in the area called Agilkia, in the smallel lobe of the comet 67P/Churyumov-Gerasimenko. It’s regolith, a layer of heterogeneous material that covers a layer of solid rock. According to estimates, in that area the regolith extends to a depth of 2 meters.
Very interesting results came from the analysis of data collected by the Philae lander’s COSAC (Cometary Sampling and Composition) instrument. It combines gas chromatograph and time-of-flight mass spectrometer to determine the compositions of soil samples and of the content of volatile components.
The samples collected from Philae after its first touchdown revealed a series of 16 organic compounds. That’s not surprising but four of them – methyl isocyanate, acetone, propionaldehyde and acetamide – were never before found in comets.
Another of Philae’s instruments, Ptolemy, was used to analyze gas samples of the coma of the comet 67P/Churyumov-Gerasimenko. In addition to the main components – water vapor, carbon monoxide and carbon dioxide – small amounts of organic components were found. Among them there’s formaldehyde, a substance important in the formation of ribose, a carbohydrate essential in the biochemistry of terrestrial life forms.
Other interesting studies concern the interaction between the comet 67P/Churyumov-Gerasimenko and solar wind. Its approach to the Sun determines a greater activity in the comet with the sublimation of the ices but the collision of water molecules and ultraviolet light causes their ionization. The solar wind’s electrical properties accelerate the ions and many of them get ejected from the coma.
Part of the ions falls on the surface of the comet instead. Some particles of the solar wind also fall on the comet and this causes the process called sputtering. In essence, the atoms on the surface get dispersed and can be ejected into space.
ESA engineers keep on trying to contact the Philae lander but the fear is that the increasing activity moved it on the surface of the comet 67P/Churyumov-Gerasimenko. The comet’s perihelion, the closest point to the Sun, is in two weeks. The Rosetta space probe will have to keep a safe distance to avoid problems due to the coma’s materials but otherwise it will be a great show, also from the scientific point of view.
