Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Active pits on Rosetta’s comet

03.07.2015

Some of the dust jets emitted from Rosetta’s comet can be traced back to active pits on its surface. They could be the remnants of collapsed cavities.

Cavities measuring up to a few hundred meters in diameter can be found under the surface of Rosetta’s comet 67P/Churyumov-Gerasimenko. They can be instable and collapse in a kind of sinkhole process. This is the result of a new study led by researchers from the Max Planck Institute for Solar System Research (MPS) in Germany, which analyses images of the comet’s surface.


Some of the observed pits are active. OSIRIS, the scientific imaging system on board Rosetta, took this image in October 2014 from a distance of seven kilometers.

© ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA


The pits allow for a look up to two hundert meters into the comet. The inner walls show layered structures. These pits can be found on the "back" of the comet in the Seth region. This images was taken in September 2014 from a distance of 28 kilometers.© ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The images show peculiar, pit-like recesses that are unlike ordinary craters and that emit dust and gas into space. In their study the researchers argue that these pits arise when cavities beneath the surface cave in. The results will be published this Thursday in the journal Nature.

Researchers under the lead of Jean-Baptiste Vincent from the MPS have studied 18 peculiar pit-like depressions all occuring in the northern hemisphere of Rosetta’s comet 67P/Churyumov-Gerasimenko. The scientists analysed images of the comet obtained by OSIRIS, the scientific imaging system on board ESA’s Rosetta spacecraft, in the period from July to December 2014. The pits' diameters vary between ten and a few hundreds of meters. They exhibit nearly vertical sidewalls and are exceptionally deep with the largest ones extending up to two hundred meters into the comet’s interior. The walls of these depressions are characterized by layers and terraces, their bottoms are mostly flat.

Earlier, similar structures had been discovered on the comets 9P/Tempel 1 and 81P/Wild 2, that have been visited by NASA’s space probes Deep Impact and Stardust in the past. “Because of their unusual morphology, these pits can be clearly distinguished from impact craters”, says OSIRIS-scientist Jean-Baptiste Vincent. “They seem to be a typical characteristic of comets”, he adds.

Some of the pits are also active: fine jets of dust are emitted from the inside walls. The scientists reached this conclusion by studying images showing the same jet from different perspectives. “In this way we obtain information on the jet’s three dimensional structure and can determine their origin on the surface”, says Vincent.

However, the emission of dust alone cannot have created these structures. Frozen gases evaporating from the comet’s surface under the influence of the Sun cannot carry enough dust with them to create holes of this size. In some cases, thousands of years of evaporation would be necessary. However, Rosetta’s comet has been advancing into the inner solar system and therewith into the Sun’s vicinity only since 1959. And even a sudden outburst of activity like the one Rosetta witnessed during the approach phase in April 2014 is unable to move enough material.

Instead, it is most likely that the pits are collapsed cavities. “Apparently, these underground voids grow larger with time until the top layer becomes instable and caves in," says Holger Sierks from the MPS, co-author of the new paper and OSIRIS Principal Investigator. As a result, fresh material is exposed at the edges of the depression. From there gases can vaporise thus charging the observed jets.

But how did the cavities come to be? The researchers currently see several possibilities. For example, the voids could date from the comet’s birth. When smaller chunks, called planetesimals, collide at low speeds such gaps may remain.

It is also conceivable, that frozen carbon dioxide and monoxide evaporating from deep within the cometary nucleus produce such subsurface structures. Frozen water evaporates at much higher temperatures. It is difficult to achieve these temperatures beneath the comet's highly insulating, superficial layer of dust by solar radiation alone. Instead, the researchers have a different heat source in view. When amorphous ice beneath the comet's surface consisting of irregularly packed molecules transforms into crystallized ice, heat is released. This might suffice to evaporate water in sufficient quantities.

"At this point, we do not favour any of these three options. Maybe even all effects work together”, says Sierks. "But we hope that the mission will brings clarity in its further course."

Already, the active pits prove useful for estimating the age of cometary surfaces. "Since the pits are active, they change with time," says Vincent. By and by the pits expand: the edges retreat forming extensive terraces. A cometary surface exhibiting deep holes is therefore rather young. Older areas present themselves as smooth plateaus.

Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is provided by a consortium led by DLR, MPS, CNES and ASI. Rosetta is the first mission in history to rendezvous with a comet, escort it as it orbits the Sun, and deploy a lander to its surface.


Contact

Dr. Birgit Krummheuer
Press Officer

Max Planck Institute for Solar System Research, Göttingen
Phone: +49 551 384979-462

Fax: +49 551 384979-240

Email: Krummheuer@mps.mpg.de


Jean-Baptiste Vincent
Max Planck Institute for Solar System Research, Göttingen
Phone: +49 5556 979-291

Email: Vincent@mps.mpg.de


Dr. Holger Sierks
OSIRIS Principal Investigator

Max Planck Institute for Solar System Research, Göttingen
Phone: +49 551 384979-242

Email: sierks@mps.mpg.de


Original publication
Jean-Baptiste Vincent et al.

Large heterogeneities in comet 67P as revealed by active pits from sinkhole collapse

Nature, 2 July 2015

Dr. Birgit Krummheuer | Max Planck Institute for Solar System Research, Göttingen
Further information:
http://www.mpg.de/9311584/active-pits-on-67P

More articles from Physics and Astronomy:

nachricht Magnetic nano-imaging on a table top
20.04.2018 | Georg-August-Universität Göttingen

nachricht New record on squeezing light to one atom: Atomic Lego guides light below one nanometer
20.04.2018 | ICFO-The Institute of Photonic Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>