Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cassini findings suggest complex story of venting at the south pole of Enceladus

31.08.2005


Evidence is mounting that the atmosphere of Enceladus, first detected by the Cassini Magnetometer instrument, is the result of venting from ground fractures close to the moon’s south pole. New findings from the close flyby of Enceladus by Cassini this past July add to the emerging picture of a small icy body, unusual in its past and present level of activity, and very different from all other icy Saturnian moons.



Within a minute of closest approach to Enceladus on July 14th, 2005, two instruments aboard the Cassini spacecraft detected material coming from the surface of the moon. The Ion and Neutral Mass Spectrometer (INMS) measured a large peak in the abundance of water vapor at approximately 35 seconds before closest approach to Enceladus, as it flew over the south polar region at an altitude of 270 kilometers (168 miles).

The High Rate Detector (HRD) of the Cosmic Dust Analyzer (CDA) observed a peak in the number of fine, powder-sized icy particles coming from the surface approximately a minute before reaching closest approach at an altitude of 460 kilometers (286 miles).


The character of these detections is very similar to the venting of vapor and fine, icy particles from the surfaces of comets when they are warmed by sunlight as they near the Sun. On Enceladus, however, it is believed that internal heat, possibly from tidal forces, is responsible for the activity. The close but different occurrences of the two detections are yielding important clues to the location of the vents and even the venting process.

“And so the plot thickens,” said Dr. Carolyn Porco, Imaging Team leader at the Space Science Institute in Boulder, Colo. “Enceladus is surprisingly warm, internally fractured and active, and we’re not sure how it comes to be that its South pole is the warmest, most active place. The fact that Enceladus is so alive, and Mimas, the moon next door and roughly the same size, is so dead, is really testing our understanding of the internal workings of planetary satellites. But we’re not complaining. We like it this way.”

Acting on the timing information, the Cassini imaging team examined images of Enceladus acquired during the same July flyby, tracing the ground track of the spacecraft across the south pole during the encounter. They noted that the maximum water vapor abundance detected by INMS occurred when Cassini was directly over one of the mid-latitude tectonic gashes that circumscribe the south polar region, suggesting at first the sub-spacecraft fracture as being the source of the vapor detected by INMS.

However, the mid-latitude fracture system is not presently a source of anomalous heat on Enceladus. Previously reported, combined results from the Composite Infrared Spectrometer (CIRS) and the Imaging Science instrument (ISS) instead indicated that an array of narrow linear cracks straddling the south pole, called ‘tiger stripes’, is the site of at least some of greatest concentrations of anomalous heat at the surface, and that mid-latitude regions are normal and cooler.

Furthermore, analysis of the timings of the INMS and CDA observations seems to indicate that the vapor and fine material are originating from the hot polar cap region, some distance away from the spacecraft’s flight path, and that the two processes – production of water vapor and ejection of fine material – are connected, as they are in a comet.

Recent numerical simulations by members of the CDA team at the University of Potsdam, Germany, aimed at reproducing the timing of the CDA observations, have shown that the majority of the icy grains originate from a source at the moon’s south pole that is distributed along the surface, like the cracks seen in the images, and not from globally distributed impacts by Saturn-system dust particles as had been previously assumed. If this is the case, then the sharpness of the peak detected in the water vapor abundances by INMS is better explained by passage of the spacecraft through the edge of a cloud of vapor that hovers over the south pole, and not through a sub-spacecraft source as suggested by the images.

The CDA analyses also shed light on the origin of the broad, diffuse E ring through which Enceladus orbits. “This new finding might explain why Enceladus is so efficient in replenishing the E ring with fresh particles,” said Dr. Frank Spahn of the University of Potsdam.

To arrive at a more complete and accurate picture of the surface environment on Enceladus will require scientists from the various Cassini instrument teams to combine their findings… something that will happen in the days ahead.

“The exploration of the mysteries of Enceladus with Cassini’s combined set of instrumentation,” said Dr. Hunter Waite, team leader of the INMS investigation at the University of Michigan in Ann Arbor, “clearly demonstrates the virtue of exploring a system as complex as Saturn’s using a very well-equipped flagship like Cassini.”

Cassini will encounter Enceladus again at very close range in March, 2008.

Preston Dyches | EurekAlert!
Further information:
http://www.ciclops.org

More articles from Physics and Astronomy:

nachricht Molecule flash mob
19.01.2017 | Technische Universität Wien

nachricht Magnetic moment of a single antiproton determined with greatest precision ever
19.01.2017 | Johannes Gutenberg-Universität Mainz

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: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland

19.01.2017 | Earth Sciences

Not of Divided Mind

19.01.2017 | Life Sciences

Molecule flash mob

19.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>