A sequence of recent Cassini images, which has been made into a brief movie, shows an arc of bright material looping around the inside edge of the G ring, a tenuous 7,000-kilometer-wide (4,400 miles) band of dust-sized icy particles lying beyond the F ring by 27,000 kilometers (16,800 miles). Cassini passed between the F and G rings during its insertion into orbit in June 2004.
The G ring arc is the same feature identified in images of this ring taken in May 2005. "We have seen the arc a handful of times over the past year," said Dr. Matt Hedman, Cassini imaging team associate working at Cornell University in Ithaca, New York. "It always appears to be a few times brighter than the rest of the G ring and very tightly confined to a narrow strip along the inside edge of the 'normal' G ring."
Imaging team members now believe this feature is long-lived and may be held together by resonant interactions with the moon Mimas of the type that corral the famed ring arcs around Neptune. "We've known since the days of Voyager that we had Jovian-type and Uranian-type rings within the rings of Saturn," said Cassini imaging team leader Dr. Carolyn Porco in Boulder, Colo., who was the first to work out the dynamics of the Neptunian arcs in Voyager observations. "Now it appears that Saturn may be home to Neptunian-type rings as well. Saturn's rings have it all!"
The researchers do not know exactly how the bright arc formed. One possibility is that a collision between small, perhaps meter-sized icy bodies orbiting within the G ring set loose a cloud of fine particles that eventually came under the influence of Mimas. But this new observation suggests that the remainder of the G ring itself may be derived from particles leaking away from this arc and drifting outwards. Future Cassini imaging observations are being planned to take a closer look at the G ring arc.
Results from Cassini's previous encounters with Enceladus indicated its south polar geysers as the primary source of the E ring particles. Now, images of the E ring with finer resolution than has ever been obtained before show telling details that appear to confirm this relationship.
The new images, taken when Cassini was in the ring plane and consequently showing an edge-on view, reveal a double-banded appearance to the ring, created because the ring is somewhat fainter close to the ring plane than it is 500-1,000 kilometers (300-600 miles) above and below. This appearance can result if the particles comprising the ring circle Saturn on inclined orbits with a very restricted range of inclinations. (A similar effect is seen in the Jupiter's gossamer ring and in the bands of dust found within the Sun's asteroid belt.)
This special condition might arise for two reasons. First, the particles being jetted out of Enceladus and injected into Saturn orbit may begin their journey around Saturn with a very restricted range of velocities and therefore inclinations. Second, the particles may begin with a large range of inclinations but those orbiting very close to the ring plane get gravitationally scattered and removed from that region.
Future studies of the E ring, including observations and dynamical models, should decide this issue. Cassini imaging team member Dr. Joseph Burns, also of Cornell, said, "We'll want images from a few other vantage points to be sure of the structure, and then we can test several models to see why these ring particles end up in such a distinct configuration."
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22.09.2017 | Forschungszentrum MATHEON ECMath
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
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Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
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