Cassini Spacecraft Reveals 101 Geysers and more on Icy Saturn Moon

This artist's rendering shows a cross-section of the ice shell immediately beneath one of Enceladus' geyser-active fractures, illustrating the physical and thermal structure and the processes ongoing below and at the surface. Image Credit: NASA/JPL-Caltech/Space Science Institute

This artist’s rendering shows a cross-section of the ice shell immediately beneath one of Enceladus’ geyser-active fractures, illustrating the physical and thermal structure and the processes ongoing below and at the surface.
Image Credit: NASA/JPL-Caltech/Space Science Institute

Scientists using mission data from NASA’s Cassini spacecraft have identified 101 distinct geysers erupting on Saturn’s icy moon Enceladus. Their analysis suggests it is possible for liquid water to reach from the moon’s underground sea all the way to its surface.
These findings, and clues to what powers the geyser eruptions, are presented in two articles published in the current online edition of the Astronomical Journal.
Over a period of almost seven years, Cassini’s cameras surveyed the south polar terrain of the small moon, a unique geological basin renowned for its four prominent “tiger stripe” fractures and the geysers of tiny icy particles and water vapor first sighted there nearly 10 years ago. The result of the survey is a map of 101 geysers, each erupting from one of the tiger stripe fractures, and the discovery that individual geysers are coincident with small hot spots. These relationships pointed the way to the geysers’ origin. Continue reading Cassini Spacecraft Reveals 101 Geysers and more on Icy Saturn Moon

Tides control the geysers of Enceladus

enceladusThe water geysers of Enceladus spew the most material when the small moon ventures farthest from Saturn, planetary scientists in the US have found. This discovery confirms a prediction of a theory that says the geysers’ strength depends on Saturn’s tide.
Discovered by the German-born English astronomer William Herschel in 1789, eight years after he spotted the planet Uranus, Enceladus is the sixth largest of Saturn’s 62 known satellites. The small moon is 238,000 km from Saturn’s centre, about two-thirds of the distance from the Earth to the Moon. Because Saturn is so massive, though, its gravity forces Enceladus to circle it every 1.37 days.
With a diameter of just 500 km, Enceladus is only one-seventh the size of the Earth’s Moon and it lacks the radioactive elements that heat the Earth’s core. This makes it an unlikely world for geysers or any other geological activity.

Icy spray
In 1980 and 1981 NASA’s Voyager 1 and 2 spacecraft flew past the ringed planet and found Enceladus’s surface unusually smooth. This suggested that something was erasing its craters. Then in 2005 the Cassini spacecraft discovered water vapour around Enceladus. Cassini soon found the surprising source: geysers around the moon’s south pole shoot water vapour and ice particles hundreds of kilometres above the surface. Some of this material settles on the surface of the moon, covering its craters.
Now planetary scientist Matthew Hedman of Cornell University and his colleagues have examined 252 near-infrared images from Cassini. “The brightness of the plume varied quite a bit,” says Hedman, who found it four times brighter when Enceladus is farthest from Saturn than when closest. These observations agree with a prediction made in a paper published in 2007 by Terry Hurford of the Goddard Space Science Center in Maryland, who had calculated how Enceladus would respond to Saturn’s tide.
Tides arise when gravity pulls on an extended object. For example, lunar gravity tugs strongest on the side of the Earth facing the Moon, lifting the sea. Likewise, on the opposite side of the Earth, the Moon’s gravity pulls our planet’s centre out from under the sea, producing a high tide on the far side as well. Elsewhere, tides from Jupiter power the fiery moon Io, which sports active volcanoes, and melt ice beneath the surface of the moon Europa….
Read more at http://physicsworld.com/cws/article/news/2013/jul/31/tides-control-the-geysers-of-enceladus

Read also: “An observed correlation between plume activity and tidal stresses on Enceladus and “Gravity controls icy moon Enceladus’s spew

Enceladus weather: Snow flurries and perfect powder for skiing

Global signature of frost deposition on Enceladus revealed in colour mapping. The top map shows a colorized map of the predicted pattern of fallout from Enceladus’s icy plumes (bus represent thicker accumulations), with the global colour patterns observed by Cassini imaging camera. The bottom map is the global 3-color map of Enceladus showing areas that are relatively bluer. These areas correspond very well with areas predicted to have a deeper accumulation of plume-generated ice particles, or “snow”. The global colour map takes advantage of Cassini’s sensitivity at ultraviolet and near infrared wavelengths and shows an enhanced colour sensitivity compared to what our eyes might see. Plume deposition map from S. Kempf and J. Schmidt; global colour map from P. Schenk.

— Global and high resolution mapping of Enceladus confirms that the weather forecast for Saturn’s unique icy moon is set for ongoing snow flurries. The superfine ice crystals that coat Enceladus’s surface would make perfect powder for skiing, according to Dr Paul Schenk of the Lunar and Planetary Institute (Houston, Texas), who will present the results at the EPSC-DPS Joint Meeting 2011 in Nantes, France on Monday 3rd October….. Continue reading Enceladus weather: Snow flurries and perfect powder for skiing

Cassini Captures Ocean-Like Spray at Saturn Moon

Dramatic plumes (cloudy, white areas), both large and small, spray water ice out from many locations along the famed "tiger stripes" near the south pole of Saturn's moon Enceladus.

PASADENA, Calif. – NASA’s Cassini spacecraft has discovered the best evidence yet for a large-scale saltwater reservoir beneath the icy crust of Saturn’s moon Enceladus. The data came from the spacecraft’s direct analysis of salt-rich ice grains close to the jets ejected from the moon.

Data from Cassini’s cosmic dust analyzer show the grains expelled from fissures, known as tiger stripes, are relatively small and predominantly low in salt far away from the moon. But closer to the moon’s surface, Cassini found that relatively large grains rich with sodium and potassium dominate the plumes. The salt-rich particles have an “ocean-like” composition and indicate that most, if not all, of the expelled ice and water vapor comes from the evaporation of liquid salt water. The findings appear in this week’s issue of the journal Nature.

“There currently is no plausible way to produce a steady outflow of salt-rich grains from solid ice across all the tiger stripes other than salt water under Enceladus’s icy surface,” said Frank Postberg, a Cassini team scientist at the University of Heidelberg, Germany, and the lead author on the paper. When water freezes, the salt is squeezed out, leaving pure water ice behind. If the plumes emanated from ice, they should have very little salt in them….. Continue reading Cassini Captures Ocean-Like Spray at Saturn Moon