Tagged: Saturn.

Cassini Sees Tropical Lakes on Saturn Moon

PASADENA, Calif. - NASA’s Cassini spacecraft has spied long-standing methane lakes, or puddles, in the “tropics” of Saturn’s moon Titan. One of the tropical lakes appears to be about half the size of Utah’s Great Salt Lake, with a depth of at least 3 feet (1 meter).

The result, which is a new analysis of Cassini data, is unexpected because models had assumed the long-standing bodies of liquid would only exist at the poles. The findings appear in this week’s issue of the journal Nature.

Where could the liquid for these lakes come from?  ”A likely supplier is an underground aquifer,” said Caitlin Griffith, the paper’s lead author and a Cassini team associate at the University of Arizona, Tucson. “In essence, Titan may have oases.”

Understanding how lakes or wetlands form on Titan helps scientists learn about the moon’s weather. Like Earth’s hydrological cycle, Titan has a “methane” cycle, with methane rather than water circulating. In Titan’s atmosphere, ultraviolet light breaks apart methane, initiating a chain of complicated organic chemical reactions. But existing models haven’t been able to account for the abundant supply of methane.

"An aquifer could explain one of the puzzling questions about the existence of methane, which is continually depleted," Griffith said. "Methane is a progenitor of Titan’s organic chemistry, which likely produces interesting molecules like amino acids, the building blocks of life."

Global circulation models of Titan have theorized that liquid methane in the moon’s equatorial region evaporates and is carried by wind to the north and south poles, where cooler temperatures cause methane to condense. When it falls to the surface, it forms the polar lakes. On Earth, water is similarly transported by the circulation, yet the oceans also transport water, thereby countering the atmospheric effects.

The latest results come from Cassini’s visual and infrared mapping spectrometer, which detected the dark areas in the tropical region known as Shangri-La, near the spot where the European Space Agency’s Huygens probe landed in 2005. When Huygens landed, the heat of the probe’s lamp vaporized some methane from the ground, indicating it had landed in a damp area.

Areas appear dark to the visual and infrared mapping spectrometer when liquid ethane or methane are present. Some regions could be shallow, ankle-deep puddles. Cassini’s radar mapper has seen lakes in the polar region, but hasn’t detected any lakes at low latitudes.

The tropical lakes detected by the visual and infrared mapping spectrometer have remained since 2004. Only once has rain been detected falling and evaporating in the equatorial regions, and only during the recent expected rainy season. Scientists therefore deduce the lakes could not be substantively replenished by rain.

"We had thought that Titan simply had extensive dunes at the equator and lakes at the poles, but now we know that Titan is more complex than we previously thought," said Linda Spilker, the Cassini project scientist based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. "Cassini still has multiple opportunities to fly by this moon going forward, so we can’t wait to see how the details of this story fill out."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s Jet Propulsion Laboratory manages the mission for NASA’s Science Mission Directorate, Washington. The visual and infrared mapping spectrometer team is based at the University of Arizona, Tucson.

  11:58 am, by ookii

Saturn’s Moon Enceladus Spreads Its Influence

NASA-Chalk up one more feat for Saturn’s intriguing moon Enceladus. The small, dynamic moon spews out dramatic plumes of water vapor and ice — first seen by NASA’s Cassini spacecraft in 2005. It possesses simple organic particles and may house liquid water beneath its surface. Its geyser-like jets create a gigantic halo of ice, dust and gas around Enceladus that helps feed Saturn’s E ring. Now, thanks again to those icy jets, Enceladus is the only moon in our solar system known to influence substantially the chemical composition of its parent planet.

In June, the European Space Agency announced that its Herschel Space Observatory, which has important NASA contributions, had found a huge donut-shaped cloud, or torus, of water vapor created by Enceladus encircling Saturn. The torus is more than 373,000 miles (600,000 kilometers) across and about 37,000 miles (60,000 kilometers) thick. It appears to be the source of water in Saturn’s upper atmosphere.

  11:33 am, by ookii 3

ckck:

Saturn’s moons Titan and Rhea, June 11th, 2006.

06:37 pm, reblogged  by ookii 3097

'Ice volcano' identified on Saturn's moon Titan

BBC-Scientists think they now have the best evidence yet for an ice volcano on Titan, the largest moon of Saturn.

The Cassini probe has spotted a 1,500m-high mountain with a deep pit in it, and what looks like a flow of material on the surrounding surface.

The new feature, which has been dubbed “The Rose”, was seen with the probe’s radar and infrared instruments.

Titan has long been speculated to have cryovolcanoes but its hazy atmosphere makes all observations very difficult.

Researchers are now wondering how active this mountain might be, and what sort of lava it could spew.

"Much of Titan’s outer material is water-ice and ammonia, and so that’s certainly one possible material that could melt at low temperatures and flow on the surface," explained Dr Randy Kirk, a Cassini radar team-member from the US Geological Survey (USGS).

12:05 pm, by ookii

Iapetus moon’s mighty ridge stirs debate

BBC-The mountainous ridge that circles the equator on the Saturnian moon Iapetus is both weird and spectacular.

Discovered in 2004, the icy rim is as much as 20km high and runs fully 1,600km from end to end.

No explanation for its existence has yet won total support; it is a puzzle.

Dr Andrew Dombard and colleagues have now made a compelling case for the ridge being the remains of a huge ring of debris that once orbited Iapetus but which eventually fell on to the moon.

"In my opinion, the ridge at Iapetus, which sits right on the equator, is one of the most amazing features that we’ve seen in the Solar System," the University of Illinois at Chicago (UIC) scientist told BBC News.

"Imagine standing at the base of this ridge. You’d be confronted with a mountain of ice that is taller than the tallest mountain on Earth and nearly as tall as Olympus Mons on Mars, the biggest volcano in the Solar System.

"And it runs ram-rod straight off in either direction. You wouldn’t see it end; you’d just see the ridge disappear over the horizon."

Dr Dombard has been explaining his team’s thinking here in San Francisco at the American Geophysical Union (AGU) Fall Meeting, the world’s largest annual gathering of Earth and planetary scientists.

The ridge was first identified in images of the 1,400km-wide moon acquired by the Cassini probe in 2004.

Dr Dombard’s group proposes that Iapetus was hit very early in its evolution by another icy body, and that this impact threw an enormous quantity of debris into space.

The researchers argue that this material could then have come together to form a mini-moon or sub-satellite. They liken the situation to the one at dwarf planet Pluto which has a small moon called Charon that was also probably the result of a collision.

Earth’s own Moon was almost certainly made this way, too.

11:58 am, by ookii

Saturn’s moon Rhea has thin atmosphere

BBC-Rhea, the second biggest moon of Saturn, has an atmosphere of oxygen and carbon dioxide, scientists say.

It is incredibly thin, however. The density of O2, for example, is probably about five trillion times less dense than the oxygen that blankets Earth.

The presence of an exosphere, as it is more properly called, was confirmed by instruments on the Cassini probe which orbits the ringed planet and its moons.

The discovery is reported in the online version of Science magazine.

Oxygen exospheres have been seen at Jupiter’s moons Europa and Ganymede, but this is the first time such a detection has been made in the Saturnian system.

  10:52 am, by ookii

New Views of Saturn’s Aurora, Captured by Cassini

NASA-PASADENA, Calif. — A new movie and images showing Saturn’s shimmering aurora over a two-day period are helping scientists understand what drives some of the solar system’s most impressive light shows. 

The new, false-color images and video are available online at: http://www.nasa.gov/cassini andhttp://saturn.jpl.nasa.gov.

The movie and images are part of a new study that, for the first time, extracts auroral information from the entire catalogue of Saturn images taken by the visual and infrared mapping spectrometer instrument (VIMS) aboard NASA’s Cassini spacecraft. These images and preliminary results are being presented by Tom Stallard, lead scientist on a joint VIMS and Cassini magnetometer collaboration, at the European Planetary Science Congress in Rome on Friday, Sept. 24.

  11:10 am, by ookii 1

A Closer Look at Daphnis

NASA’s Cassini spacecraft has captured the closest images of Saturn’s moon Daphnis to date. In these raw images obtained on July 5, 2010, the moon can be seen orbiting in a rift known as the Keeler Gap in one of Saturn’s rings.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA’s Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter.

More information about the Cassini-Huygens mission is at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

  12:25 pm, by ookii 1