Rosetta’s target «Chury» and other comets observed by space missions show common evidence of layered structures and bi-lobed shapes. With 3D computer simulations Martin Jutzi, astrophysicist at the University of Bern, was able to reconstruct the formation of these features as a result of gentle collisions and mergers. The study has now been published online in the journal «Science Express».
In a video sequence based on a computer simulation two icy spheres with a diameter of about one kilometer are moving towards each other. They collide at bicycle speed, start to mutually rotate and separate again after the smaller body has left traces of material on the larger one.
The time sequence shows that the smaller object is slowed down by mutual gravity. After about 14 hours it turns back and impacts again a day after the first collision. The two bodies finally merge to form one body that somehow looks familiar: The bi-lobed frame resembles the shape of comet 67P/Churyumov-Gerasimenko imaged by ESA’s Rosetta mission.
100 simulations performed
The simulation is part of a study published in «Science Express» by Bernese astrophysicist Martin Jutzi and his US colleague Erik Asphaug (Arizona State University). With their three-dimensional computer models the researchers reconstruct what happened in the early solar system.
«Comets or their precursors formed in the outer planets region, possibly millions of years before planet formation», explains Martin Jutzi. «Reconstructing the formation process of comets can provide crucial information about the initial phase of planet formation, for instance, the initial sizes of the building blocks of planets, the so-called planetesimals or cometesimals in the outer solar system.»
About 100 simulations were performed, each of them taking one to several weeks to complete, depending on the collision type. The work was supported by the Swiss National Science Foundation through the Ambizione program and in part carried out within the frame of the Swiss National Centre for Competence in Research «PlanetS».
67P/Churyumov-Gerasimenko isn’t the only comet showing a bi-lobed shape and evidence for a layered structure. Crashing on 9P/Tempel 1 in 2005, NASA’s Deep Impact showed similar layers, a feature that is also presumed on two other comets visited by NASA missions.
Half of the comet nuclei that spacecraft have observed so far – among them comets 103P/Hartley 2 and 19P/Borelly – have bi-loped shapes. «How and when these features formed is much debated, with distinct implications for solar system formation, dynamics, and geology», says Martin Jutzi.
Primordial remnants of a quiet phase
In their study, the researchers applied 3D collisional models, constrained by these shape and topographic data, to understand the basic accretion mechanism and its implications for internal structure. As their three-dimensional computer simulations indicate, the major structural features observed on cometary nuclei can be explained by the pairwise low velocity accretion of weak cometesimals. The model is also compatible with the observed low bulk densities of comets as the collisions result in only minor compaction.
«These slow mergers might represent the quiet, early phase of planet formation around 4.5 billion years ago, before large bodies excited the system to disruptive velocities, supporting the idea that cometary nuclei are primordial remnants of early agglomeration of small bodies», says Martin Jutzi. Alternatively, the same processes of coagulation might have occurred among debris clumps ejected from much larger parent bodies. Along with future space missions using radar to directly image internal structure, the 3D computer simulations are an important step to clarify the question of how the cometary nuclei were assembled.
M. Jutzi, E. Asphaug, «The shape and structure of cometary nuclei as a result of low velocity accretion», Science Express, 2015
Nathalie Matter | Universität Bern
Igniting a solar flare in the corona with lower-atmosphere kindling
29.03.2017 | New Jersey Institute of Technology
NASA spacecraft investigate clues in radiation belts
28.03.2017 | NASA/Goddard Space Flight Center
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
29.03.2017 | Materials Sciences
29.03.2017 | Physics and Astronomy
29.03.2017 | Earth Sciences