News story

Close-up of boulder Cheops

Scientists name one of the largest boulders on Rosetta’s comet after Egyptian pyramid.

Image of a group of boulders reminding scientists of the Giza Necropolis.
The group of boulders in the centre of this image reminded scientists of the Giza Necropolis. The largest boulder has therefore been named Cheops. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

The scientific imaging system OSIRIS on board Europe’s Rosetta spacecraft has caught a spectacular glimpse of one of the many boulders that cover the surface of comet 67P/Churyumov-Gerasimenko. With a maximum extension of 45 meters it is one of the larger structures of this kind on the comet and stands out among a group of boulders located on the lower side of 67P’s larger lobe. Since this cluster of boulders reminded the scientists of the pyramids of Giza, the boulder has been named Cheops after the largest pyramid within the Giza Necropolis. The boulder-like structures that Rosetta has revealed on the surface of 67P in the past months are one of the comet’s most striking and mysterious features.

Close-up of the boulder Cheops as it casts a long shadow on the surface of comet 67P/Churyumov-Gerasimenko.
Close-up of the boulder Cheops as it casts a long shadow on the surface of comet 67P/Churyumov-Gerasimenko. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

The large boulder now dubbed Cheops was seen for the first time in images obtained in early August upon Rosetta’s arrival at the comet. In the past weeks as Rosetta has navigated closer and closer to the comet’s surface, OSIRIS imaged the unique structure again – but this time with a much higher resolution of 50 centimeters per pixel.

As many of the smaller and larger boulders currently being mapped by the OSIRIS team, Cheops stands out from the darker underground. The highly resolved image now startles scientists with striking details.

The surface of Cheops seems to be very craggy and irregular,

OSIRIS Principle Investigator Holger Sierks from the Max Planck Institute for Solar System Research (MPS) in Germany describes. Especially intriguing are small patches on the boulder’s surface displaying the same brightness and texture as the underground.

It looks almost as if loose dust covering the surface of the comet has settled in the boulder’s cracks. But, of course, it is much too early to be sure,

says Sierks.

Apart from their size distribution, almost all properties of 67P’s many boulders are still a mystery to researchers. What material are they made of? What are their physical properties such as density and stability? How where they created? As OSIRIS continues to monitor the comet’s surface in the next months the team hopes for clues.

If, for example, the boulders are exposed by cometary activity or are displaced following the comet’s gravity field, we should be able to track this down in our images,

says Sierks.

Today, Rosetta will begin its Close Observation Phase reaching a distance of only 10 kilometers from the comet’s surface – and giving OSIRIS a chance at an even closer view of one of 67P’s many mysteries.

Rosetta and the UK

With funding from the UK Space Agency and the Science and Technology Facilities Council (STFC), Rosetta is a mission with significant UK involvement from industry and science.

One of the main challenges for all the companies designing instruments for Rosetta has been to ensure the components remain intact for ten years, while the spacecraft makes its way to the comet, and then work perfectly when it gets there. Not an easy task! Further information about the UK’s involvement can be found at

Industry involvement

  • Airbus Defence and Space, based in Stevenage, was the major subcontractor for the Rosetta platform.
  • e2v, based in Chelmsford, designed and supplied the high performance imaging devices used in the Navigation Camera, OSIRIS narrow field and wide field cameras and VITRIS-M instruments on the orbiter and ROLIS and CIVA instruments on the lander
  • ABSL Space Products provided innovative batteries for the spacecraft and lander. These are smaller, lighter and much more reliable than the traditional nickel-cadmium batteries.
  • ERS Technology supported the development of many subsystems including the reactions wheels, solar array drive motors, Philae harpoon motors and developed the lubricant for the atomic force microscope on the Micro-Imaging Dust Analysis System (MIDAS).
  • Technology created by CGI Group helped to explore some of the issues involved in such a long mission. The company was also involved in the development of the Rosetta on board software.
  • Moog provided tanks to store the helium used by the lander.
  • STFC’s RAL Space co-developed the Ptolemy instrument with the Open University and designed the thermal insulation for the GIADA and VIRTIS instruments as well as the Philae lander itself.
  • SciSys UK Ltd is responsible for the spacecraft Mission Control System development and maintenance. In recognition of this work on the Rosetta and the Beagle 2 missions, SciSys were awarded the title of “Innovator of the Year” by the UK Computing Awards for Excellence 2004.
  • Surrey Satellite Technology Limited (SSTL) designed a wheel that will stabilise the probe as it descends and lands on the comet.
  • Telespazio VEGA was involved in many aspects of the Rosetta mission, from the overall design of the spacecraft to the on-board software.

Science involvement

UK scientists are involved in ten of the 21 experiments that Rosetta will carry out during its mission:

  • The Open University in collaboration with STFC RAL Space designed and built the Ptolemy instrument on the lander and is contributing scientific expertise to the GIADA, MUPUS and SESAME instrument teams.
  • The University of Kent will be helping to analyse the results from the OSIRIS instrument and have been involved in observing Rosetta’s target comet from ground-based telescopes to aid mission planning.
  • Imperial College London and University College London’s Mullard Space Science Laboratory (MSSL) supply the team studying the comet’s plasma.
  • Scientists at Oxford University are part of the science team for VIRTIS.
  • Queen Mary College at the University of London will be investigating the results of the CONSERT instrument.
  • Researchers from Queen’s University Belfast are part of the team observing Rosetta’s target comet using ground-based telescopes.
Published 10 October 2014