Geysers spew ice and gas on Saturn's moon

Spacecraft Cassini finds evidence of gargoyle on Enceladus

Cassini false-color image of the Saturn moon Enceladus. The Staubfontainen due to the ice volcanism are clearly visible above the southern polar region (lower left corner). © NASA / JPL
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At the south pole of Saturn's moon Enceladus, geysers spray ice and gas fountains over the surface. For this, scientists have found clear indications of images and spectral measurements of the spacecraft Cassini. Thus, volcanism was already detected in the third celestial body in the solar system - in addition to the Earth and the Jupiter moon "Io" describe their discovery in the current issue of the science magazine Science.

The geysers hurl ice and gases up to 490 kilometers into the Enceladus area, supplying material to the outer ring of Saturn. The reservoirs from which the geysers feed may be only a few meters below the surface of the small 500 m diameter ice moon. The position of the ice volcanoes coincides with geologically young, warmer structures in the south pole region of the ice moon. Probably the ice particles form in the deep cracks of water vapor.

Water ice and carbon dioxide

During the flyby of Cassini to Enceladus on November 27, 2005, the camera system observed in the back light fine rays of particles that emanate from the South Pole and can be traced far into space. "In the data from the Cassini imaging spectrometer recorded at the same time, we clearly see that the geochemical composition of the South Pole is different and, above all, more complex than on the rest of the lunar surface, " reports Ralf Jaumann from the Institute for Planetary Research of the German Aerospace Center Space flight (DLR). "In addition to pure, crystalline and amorphous water ice, it also contains carbon dioxide and organic molecules, which is a very clear indication that the Moon is still geologically active in this area." The study on the composition and physical properties of the Enceladus surface is led by Robert Brown of the Lunar and Planetary Laboratory of the University of Arizona at Tucson.

Thomas Roatsch of the DLR Institute for Planetary Research, one of the authors of the scientific article of the ISS team (Imaging Science Subsystem), calculated for the Cassini camera team from the image data of the near fly-bys from February, March and July 2005 the exact image maps of the ice moon, the serve as a basis for the geological mapping of the moon. "In our mosaics of the South Pole, a series of slightly curved, parallel fracture structures are immediately noticeable, and it is likely that these" trenches "- called" tiger stripes "by the scientists - eject the water at high pressure, as the spectrometer data shows striking changes." The DLR team produces image mosaics and maps as well as impact crater statistics for the age determination of several Saturn moons in cooperation with Professor Gerhard Neukum of the Freie Universität Berlin, who is a member of the Cassini camera team.

Geologically active for four million years

Roland Wagner from the DLR Institute for Planetary Research, Dr. med. Carolyn Porco of the Space Science Institute of Boulder, Colorado, was involved in determining the different ages of the lunar surface. "Compared to the rest of Enceladus' surface, the S dpol region is much younger, " explains the scientist, "given the low density of impact craters, we assume that the areas between the "Tiger stripes" are much younger than a million years old - a geologically extremely young age. " As other areas on Enceladus are much older, the moon seems to have been geologically active for at least four billion years. display

Actually, at a distance of almost a billion and a half kilometers from the sun, it is too cold for a moon of Saturn, especially since it is as small as Enceladus, to harbor water under its ice sheet in liquid form. In the case of Enceladus, there seems to be only one source of energy that could melt ice, thus causing the formation of water reservoirs. The tidal forces acting on the body could generate heat through interaction with Saturn and the neighboring moons Mimas, Tethys, and Dione. On the other hand, the 500-kilometer-diameter moon is too small for current models of heat energy generation - such as the radioactive decay of elements that also generates heat inside the earth - to apply here as well Would be like with larger satellites in the outer solar system.

Enceladus is not the first body in the outer solar system that is believed to have water under its surface. With measurements of the space probe Galileo this was also found in the 1990s for the Jupiter moons of Europe and probably also Ganymed. But in contrast to these bodies, the water that rises from Enceladus' "tiger stripes" seems to be almost directly below the surface. Scientists believe it is not excluded that the water-bearing layers of the ice moons of Jupiter and Saturn could even produce forms of organic life.

(German Aerospace Center (DLR) / MPG for Nuclear Physics, 13.03.2006 - AHE)