July 17, 2014

A comet in two parts

The nucleus of comet 67P/Churyumov–Gerasimenko seems to be composed of two parts. The latest pictures have caused something of a stir among scientists.
17 June 2014

14 July 2014

As Europe’s Rosetta spacecraft slowly closes in on comet 67P/Churyumov–Gerasimenko, we are beginning to get a sense of its rather unusual shape. The latest pictures, captured by the OSIRIS* camera on 14 July at a separation of about 12,000 km, confirm the highly irregular shape of the comet’s icy core, already suggested by previous images. 67P/Churyumov–Gerasimenko is clearly different from any other comet visited by a space probe in the past.

To make the unusual outline of the comet easier to see, it is possible to interpolate the highly pixelated images received, making them smoother. “Of course, there is still some uncertainty in these processed and filtered pictures, and the surface will not be as smooth as it appears here,” explains Carsten Güttler of the Max Planck Institute for Solar System Research (MPS) in Germany. “But they are giving us an initial idea.

Two separate parts?

The distance between Rosetta and 67P/Churyumov-Gerasimenko is no longer astronomical,” explains Holger Sierks (MPS), OSIRIS Principal Investigator. “It’s a journey of less than 12,000 km, similar to the distance between Germany and Hawaii.

At this relatively close range, the OSIRIS camera is able to take pictures of the comet at increasingly higher resolutions. The images acquired on 14 July clearly show its astonishing shape: 67P/Churyumov–Gerasimenko’s nucleus is composed of two parts!

It’s like nothing we’ve ever seen,” says Carsten Güttler (MPS). “It looks a bit like a rubber duck, with a body and a head,” he adds with a smile.

Exactly why 67P/Churyumov–Gerasimenko’s nucleus is shaped like this is not clear. “At this stage, we don’t know enough about the comet, so we can only speculate,” adds Holger Sierks. Over the next few months, scientists hope to learn much more about the comet’s physical properties and mineral composition, helping them to determine whether its ‘body’ and ‘head’ were once two separate entities.

*The scientific imaging system OSIRIS was built by a consortium led by the Max Planck Institute for Solar System Research (Germany) in collaboration with CISAS, University of Padova (Italy), the Laboratoire d'Astrophysique de Marseille (France), the Instituto de Astrofísica de Andalucia, CSIC (Spain), the Scientific Support of the European Space Agency (The Netherlands), the Instituto Nacional de Técnica Aeroespacial (Spain), the Universidad Politéchnica de Madrid (Spain), the Department of Physics and Astronomy of Uppsala University (Sweden), and the Institute of Computer and Network Engineering of the TU Braunschweig (Germany). OSIRIS was financially supported by the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), and Sweden (SNSB) and the ESA Technical Directorate.


Rosetta is an ESA mission with contributions from its member states and NASA.