Close-up of a comet’s dust
Comet 67P/Churyumov-Gerasimenko by Rosetta’s OSIRIS narrow-angle camera on 3 August from a distance of 285 km. The image resolution is 5.3 metres/pixel.
At the beginning of August, ESA’s Rosetta spacecraft became the first spacecraft to rendezvous with a comet, opening a new chapter in Solar System exploration. While Rosetta and its scientific instruments will watch how the comet evolves as heating by the Sun increases, observing how its coma develops and how the surface changes over time, the lander Philae and its instruments will be tasked with making complementary in situ measurements at the comet’s surface. (The harpoon for anchoring the lander on the comet’s surface has also been developed and built under MPE leadership.)
The on-board COSIMA instrument exposed its first targets on the early morning of 11 August to collect cometary dust grains in the inner coma of the comet 67P/Churyumov-Gerasimenko. One of the targets, imaged on 24 August, revealed numerous newly collected cometary grains, not visible in the images taken one week earlier (see figure). These are the very first microscopic images of cometary grains collected at a distance of just 100 km from the comet’s nucleus, swept along in the comet’s coma.
The microscope of COSIMA detected several cometary grains collected in the inner coma of 67P/Churyumov-Gerasimenko in the time period Aug 17 to 24, while Rosetta accompanied the nucleus at about 100 km distance. The sizes of the largest grains are about 50 and 70 micrometres. The illumination of the target is from the right and the length of shadows is proportional to the heights of the cometary dust grain. The size of the dust collecting target is 1x1 cm^2 and the optical resolution is 14 micrometres/pixel.
Presently the COSIMA science team is extracting the location of the cometary grains collected on the target surface. They are investigating the grain properties and are preparing the COSIMA instrument for the first chemical composition analysis of this cometary material. Comets are considered to be primitive building blocks of the Solar System and may have helped to ‘seed’ our Earth with the ingredients for life. But many fundamental questions about these enigmatic objects remain, and through a comprehensive, close-up study of the comet, Rosetta aims to unlock the secrets within.
About COSIMA:
COSIMA was built by a consortium led by Jochen Kissel at the Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany in collaboration with Laboratoire de Physique et Chimie de l'Environnement et de l'Espace, Orléans, France, Institut d'Astrophysique Spatiale, CNRS / Université Paris Sud, Orsay, France, Finnish Meteorological Institute, Helsinki, Finland, Universität Wuppertal, Wuppertal, Germany, von Hoerner und Sulger GmbH, Schwetzingen, Germany, Universität der Bundeswehr, Neubiberg, Germany, Institut für Physik, Forschungszentrum Seibersdorf, Seibersdorf, Austria, Institut für Weltraumforschung, Österreichische Akademie der Wissenschaften, Graz, Austria and is lead by Martin Hilchenbach at the Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany The support of the national funding agencies of Germany (DLR), France (CNES), Austria, Finland and the ESA Technical Directorate is gratefully acknowledged. We thank the Rosetta Science Ground Segment at ESAC, the Rosetta Mission Operations Centre at ESOC and the Rosetta Project at ESTEC for their outstanding work enabling the science return of the Rosetta Mission.