Tagged: Cassini.

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

Icy Moons through Cassini’s Eyes

These raw, unprocessed images of Saturn’s moons Enceladus, Janus and Dione were taken on March 27 and 28, 2012, by NASA’s Cassini spacecraft.

Cassini passed Enceladus first on March 27, coming within about 46 miles (74 kilometers) of the moon’s surface. The encounter was primarily designed for Cassini’s ion and neutral mass spectrometer, which “tasted” the composition of Enceladus’ south polar plume. Other instruments, including the Cassini plasma spectrometer and composite infrared spectrometer, also took measurements.

Before the closest approach of this encounter, Cassini’s cameras imaged the plume, which is comprised of jets of water ice and vapor, and organic compounds emanating from the south polar region.  Later, the cameras captured a nine-frame mosaic of the surface of the moon’s leading hemisphere as the spacecraft left the moon.

After the Enceladus encounter, Cassini passed the small moon Janus with a closest approach distance of 27,000 miles (44,000 kilometers). The planet was in the background in some of these views.

Early on March 28, the spacecraft flew by Dione at a distance of 27,000 miles (44,000 kilometers) and collected, among other observations, a nine-frame mosaic depicting the side of the moon that faces away from Saturn in its orbit.

 All of Cassini’s raw images can be seen at http://saturn.jpl.nasa.gov/photos/raw/ .

12:00 pm, by ookii

Cassini Returns Images of Bright Jets at Enceladus

NASA’s Cassini spacecraft successfully dipped near the surface of Saturn’s moon Enceladus on Nov. 30. 

NASA’s Cassini spacecraft successfully dipped near the surface of Saturn’s moon Enceladus on Nov. 30. Though Cassini’s closest approach took it to within about 48 kilometers (30 miles) of the moon’s northern hemisphere, the spacecraft also captured shadowy images of the tortured south polar terrain and the brilliant jets that spray out from it.

Many of the raw images feature darkened terrain because winter has descended upon the southern hemisphere of Enceladus. But sunlight behind the moon backlights the jets of water vapor and icy particles. In some images, the jets line up in rows, forming curtains of spray.

The new raw images can be seen at http://saturn.jpl.nasa.gov/photos/raw/ .

  11:57 pm, by ookii 1

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

Cassini Double Play: Enceladus and Titan

NASA-About a month and a half after its last double flyby, NASA’s Cassini spacecraft will be turning another double play this week, visiting the geyser moon Enceladus and the hazy moon Titan. The alignment of the moons means that Cassini can catch glimpses of these two contrasting worlds within less than 48 hours, with no maneuver in between.

Cassini will make its closest approach to Enceladus late at night on May 17 Pacific time, which is in the early hours of May 18 UTC. The spacecraft will pass within about 435 kilometers (270 miles) of the moon’s surface.

  07:36 pm, by ookii