Enceladus has an Atmosphere -- NASA

Cassini Finds an Atmosphere on Saturn's Moon Enceladus 03.16.05

The Cassini spacecraft's two close flybys of Saturn's icy moon Enceladus have revealed that the moon has a significant atmosphere. Scientists, using Cassini's magnetometer instrument for their studies, say the source may be volcanism, geysers, or gases escaping from the surface or the interior.

When Cassini had its first encounter with Enceladus on Feb. 17 at an altitude of 1,167 kilometers (725 miles), the magnetometer instrument saw a striking signature in the magnetic field. On March 9, Cassini approached to within 500 kilometers (310 miles) of Enceladus' surface and obtained additional evidence.

The observations showed a bending of the magnetic field, with the magnetospheric plasma being slowed and deflected by the moon. In addition, magnetic field oscillations were observed. These are caused when electrically charged (or ionized) molecules interact with the magnetic field by spiraling around the field line. This interaction creates characteristic oscillations in the magnetic field at frequencies that can be used to identify the molecule. The observations from the Enceladus flybys are believed to be due to ionized water vapor.

"These new results from Cassini may be the first evidence of gases originating either from the surface or possibly from the interior of Enceladus," said Dr. Michele Dougherty, principal investigator for the Cassini magnetometer and professor at Imperial College in London. In 1981, NASA's Voyager spacecraft flew by Enceladus at a distance of 90,000 kilometers (56,000 miles) without detecting an atmosphere. It's possible detection was beyond Voyager's capabilities, or something may have changed since that flyby.

This is the first time since Cassini arrived in orbit around Saturn last summer that an atmosphere has been detected around a moon of Saturn, other than its largest moon, Titan. Enceladus is a relatively small moon. The amount of gravity it exerts is not enough to hold an atmosphere very long. Therefore, at Enceladus, a strong continuous source is required to maintain the atmosphere.

The need for such a strong source leads scientists to consider eruptions, such as volcanoes and geysers. If such eruptions are present, Enceladus would join two other such active moons, Io at Jupiter and Triton at Neptune. "Enceladus could be Saturn's more benign counterpart to Jupiter's dramatic Io," said Dr. Fritz Neubauer, co-investigator for the Cassini magnetometer, and a professor at the University of Cologne in Germany.

Since the Voyager flyby, scientists have suspected that this moon is geologically active and is the source of Saturn's icy E ring. Enceladus is the most reflective object in the solar system, reflecting about 90 percent of the sunlight that hits it. If Enceladus does have ice volcanoes, the high reflectivity of the moon's surface might result from continuous deposition of icy particles originating from the volcanoes.

Enceladus' diameter is about 500 kilometers (310 miles), which would fit in the state of Arizona. Yet despite its small size, Enceladus exhibits one of the most interesting surfaces of all the icy satellites.

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During its very close flyby on March 9, 2005, the Cassini spacecraft captured this false-color view of Saturn's moon Enceladus, which shows the wide variety of this icy moon's geology.

Some geological regions on Enceladus are old and retain large numbers of impact craters; younger areas exhibit many generations of tectonic troughs and ridges. Subtle differences in color may indicate different ice properties, such as grain sizes, that will help unravel the sequence of geologic events leading to the current strange landscape.

This false-color view is a composite of individual frames obtained using filters sensitive to green (centered at 568 nanometers) and infrared light (two infrared filters, centered at 752 and 930 nanometers respectively). The view has been processed to accentuate subtle color differences. The atmosphere of Saturn forms the background of this scene (its color has been rendered grey to allow the moon to stand out).

The Sun illuminates Enceladus from the left, leaving part of it in shadow and blocking out part of the view of Saturn. This view shows the anti-Saturn hemisphere, centered nearly on the equator.

The images comprising this view were taken with the Cassini spacecraft narrow-angle camera at a distance of approximately 94,000 kilometers (58,000 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 48 degrees. Resolution in the image is about 560 meters (1,800 feet) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . For additional images visit the Cassini imaging team homepage http://ciclops.org .

Credit: NASA/JPL/Space Science Institute

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Elrohir said:

Any information on how thick the atmosphere is, and of what type of gas?

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The observations showed a bending of the magnetic field, with the magnetospheric plasma being slowed and deflected by the moon. In addition, magnetic field oscillations were observed. These are caused when electrically charged (or ionized) molecules interact with the magnetic field by spiraling around the field line. This interaction creates characteristic oscillations in the magnetic field at frequencies that can be used to identify the molecule. The observations from the Enceladus flybys are believed to be due to ionized water vapor.

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Enceladus is a relatively small moon. The amount of gravity it exerts is not enough to hold an atmosphere very long. Therefore, at Enceladus, a strong continuous source is required to maintain the atmosphere.

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Bozo Erectus said:

King, my point is that if our solar system harbors intelligent life, and numerous worlds with their own bacterial ecosystems, then there must be alot of life out there waiting for us. Some of it intelligent, some of it not.

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Bozo Erectus said:

Raser, Im looking forward to meeting the Kzin more than I am the Klingons. Klingons are just pissed off humans with cheesegrator browridges.

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Bozo Erectus said:

Those basterial ecosystems on other planets are in much greater danger of being harmed through contamination than we are.

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FearlessLeader2 said:

"In 1981, NASA's Voyager spacecraft flew by Enceladus at a distance of 90,000 kilometers (56,000 miles) without detecting an atmosphere. It's possible detection was beyond Voyager's capabilities, or something may have changed since that flyby."

Nasa is embracing catastrophism?

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Bozo Erectus said:

Man theres water all over the place! Theres more than one home for life in our own solar system, imagine how much life is out there in other solar systems waiting for us to get our act together and go check it out

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Quasar1011 said:

I can imagine. Zero.

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Quasar1011 said:

I can imagine. Zero.

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Bozo Erectus said:

Zilch? Nada? Zip? The entire universe, nothing? Do you have anything besides bible passages to back that up?

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Bozo Erectus said:

Zilch? Nada? Zip? The entire universe, nothing? Do you have anything besides bible passages to back that up?

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Bozo Erectus said:

Babbler, the evidence is our own solar system. Does it seem logical to you that in a universe filled with trillions of trillions of solar systems, that ours would be the only one with life?

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Quasar1011 said:

Seems logical to me.

By the way, there really aren't trillions of Solar systems. There is only one. There are certainly billions of planetary systems, but only our star is named Sol, giving rise to the Solar system. A planet in orbit around Antares would be part of the Antarean system, for example.

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Bozo Erectus said:

Okay Quasar, Im sure it would be very interesting, although to be honest, if its in math, it might as well be Sanskrit to me. Last I heard though, all you really need for life is a heat source and water.

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