Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Saturn’s moon Enceladus may have rolled over to put a hot spot at the pole

01.06.2006


Enceladus, a small icy moon of Saturn, may have dramatically reoriented relative to its axis of rotation, rolling over to put an area of low density at the moon’s south pole. According to a new study, this reorientation process could explain the polar location of a region where NASA’s Cassini spacecraft recently observed icy jets and plumes indicating active geysers of water vapor spewing from the moon’s surface.



"When we saw the Cassini results, we were surprised that this hot spot was located at the pole. So we set out to explain how it could end up at the pole if it didn’t start there," said Francis Nimmo, assistant professor of Earth sciences at the University of California, Santa Cruz.

Coauthor Robert Pappalardo worked on the study while at the University of Colorado and is now at NASA’s Jet Propulsion Laboratory in Pasadena. Nimmo and Pappalardo have proposed a reorientation process driven by an upwelling of warm, low-density material inside Enceladus. A similar reorientation process may also have operated on other small moons in the solar system, such as Uranus’s moon Miranda, they said. The researchers described their findings in a paper published in the June 1 issue of the journal Nature.


Nimmo and Pappalardo calculated the effects of a low-density blob beneath the surface of Enceladus and showed that this could indeed cause the moon to roll over and put the low-density blob at the pole. Rotating bodies, including planets and moons, are most stable if most of their mass is close to the equator. Therefore, any redistribution of mass within the object can cause instability with respect to the axis of rotation. The resulting reorientation will tend to position excess mass at the equator and, conversely, areas of low density at the poles, Nimmo said.

"The whole body rolls over, while the spin axis stays fixed," he said.

An upwelling of warm, low-density material could also help to explain the high heat flux and striking surface features observed at Enceladus’s south pole. These features include not only geysers, but also a "tiger stripe" pattern suggesting fault lines caused by tectonic stress.

"The whole area is hotter than the rest of the moon, and the stripes are hotter than the surrounding surface, suggesting that there is a concentration of warm material below the surface," Nimmo said.

Internal heating of Enceladus probably results from its eccentric orbit around Saturn. The gravitational pull Enceladus feels from Saturn changes in the course of its orbit, and the resulting tidal forces generate heat inside the moon.

"Enceladus gets squeezed and stretched by tidal forces, and that mechanical energy is transformed into heat energy in the interior," Nimmo said.

The upwelling blob (called a "diapir") may be within either the icy shell or the underlying rocky core of Enceladus, he said. In either case, as the material heats up it expands and becomes less dense, then rises toward the surface.

The reorientation scenario leads to testable predictions, Nimmo said. For example, the leading hemisphere of a moon as it travels through space should have more impact craters than the trailing hemisphere. But if the moon rolls over, the pattern of impact craters will also be reoriented. A low-density mass may also produce an observable anomaly in the moon’s gravitational field.

Additional observations of Enceladus are planned for the Cassini mission and should enable the researchers to test these predictions, Nimmo said.

Tim Stephens | EurekAlert!
Further information:
http://www.nasa.gov/cassini
http://saturn.jpl.nasa.gov
http://www.ucsc.edu

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: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

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

Im Focus: Highly precise wiring in the Cerebral Cortex

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.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

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...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Fraunhofer ISE Pushes World Record for Multicrystalline Silicon Solar Cells to 22.3 Percent

25.09.2017 | Power and Electrical Engineering

Usher syndrome: Gene therapy restores hearing and balance

25.09.2017 | Health and Medicine

An international team of physicists a coherent amplification effect in laser excited dielectrics

25.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>