There's Water in... Titan!

NASA Confirms Liquid Lake On Saturn Moon

07.30.08

This artist concept shows a mirror-smooth lake on the surface of the smoggy moon Titan. Image credit: NASA/JPL/Space Science Institute
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PASADENA, Calif. -- NASA scientists have concluded that at least one of the large lakes observed on Saturn’s moon Titan contains liquid hydrocarbons, and have positively identified the presence of ethane. This makes Titan the only body in our solar system beyond Earth known to have liquid on its surface.

Scientists made the discovery using data from an instrument aboard the Cassini spacecraft. The instrument identified chemically different materials based on the way they absorb and reflect infrared light. Before Cassini, scientists thought Titan would have global oceans of methane, ethane and other light hydrocarbons. More than 40 close flybys of Titan by Cassini show no such global oceans exist, but hundreds of dark, lake-like features are present. Until now, it was not known whether these features were liquid or simply dark, solid material.

"This is the first observation that really pins down that Titan has a surface lake filled with liquid," said Bob Brown of the University of Arizona, Tucson. Brown is the team leader of Cassini’s visual and mapping instrument. The results will be published in the July 31 issue of the journal Nature.

Ethane and several other simple hydrocarbons have been identified in Titan’s atmosphere, which consists of 95 percent nitrogen, with methane making up the other fiver percent. Ethane and other hydrocarbons are products from atmospheric chemistry caused by the breakdown of methane by sunlight.

Some of the hydrocarbons react further and form fine aerosol particles. All of these things in Titan's atmosphere make detecting and identifying materials on the surface difficult, because these particles form a ubiquitous hydrocarbon haze that hinders the view. Liquid ethane was identified using a technique that removed the interference from the atmospheric hydrocarbons.

The visual and mapping instrument observed a lake, Ontario Lacus, in Titan’s south polar region during a close Cassini flyby in December 2007. The lake is roughly 20,000 square miles (7,800 square miles) in area, slightly larger than North America's Lake Ontario.

"Detection of liquid ethane confirms a long-held idea that lakes and seas filled with methane and ethane exist on Titan," said Larry Soderblom, a Cassini interdisciplinary scientist with the U.S. Geological Survey in Flagstaff, Ariz. "The fact we could detect the ethane spectral signatures of the lake even when it was so dimly illuminated, and at a slanted viewing path through Titan's atmosphere, raises expectations for exciting future lake discoveries by our instrument."

The ethane is in a liquid solution with methane, other hydrocarbons and nitrogen. At Titan’s surface temperatures, approximately 300 degrees Fahrenheit below zero, these substances can exist as both liquid and gas. Titan shows overwhelming evidence of evaporation, rain, and fluid-carved channels draining into what, in this case, is a liquid hydrocarbon lake.

Earth has a hydrological cycle based on water and Titan has a cycle based on methane. Scientists ruled out the presence of water ice, ammonia, ammonia hydrate and carbon dioxide in Ontario Lacus. The observations also suggest the lake is evaporating. It is ringed by a dark beach, where the black lake merges with the bright shoreline. Cassini also observed a shelf and beach being exposed as the lake evaporates.

"During the next few years, the vast array of lakes and seas on Titan's north pole mapped with Cassini's radar instrument will emerge from polar darkness into sunlight, giving the infrared instrument rich opportunities to watch for seasonal changes of Titan's lakes," Soderblom said.

More information is available at: http://www.nasa.gov/cassini, http://saturn.jpl.nasa.gov and http://wwwvims.lpl.arizona.edu .

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 Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The Visual and Infrared Mapping Spectrometer team is based at the University of Arizona.

Close-Up Images of 'Snow Queen' Show Changes

Close-Up Images of 'Snow Queen' Show Changes

07.29.08

NASA's Phoenix Mars Lander collected a soil sample and attempted to deliver some of it to a laboratory oven on the deck during the mission's 62nd Martian day, or sol, (July 28, 2008). Image credit: NASA/JPL-Caltech/University of Arizona/Max Planck Institute
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Animations and videos TUCSON, Ariz. -- A distinctive hard-surface feature called "Snow Queen" beneath NASA's Phoenix Mars Lander visibly changed sometime between mid-June and mid-July, close-up images from the Robotic Arm Camera show.

Cracks as long as 10 centimeters, or about four inches, have appeared. A seven-millimeter (less than one-third inch) pebble or clod not seen there before has popped up on the surface. And some smooth texture on Snow Queen has subtly roughened.

Phoenix's Robotic Arm Camera, or RAC, took its first close-up image of Snow Queen on May 31, 2008, the sixth Martian day, or sol, after the May 25 landing. Thruster exhaust blew away surface soil covering Snow Queen as Phoenix landed, exposing a hard layer comprising several smooth, rounded cavities.

"Images taken since landing showed these fractures didn't form in the first 20 sols of the mission," Phoenix co-investigator Mike Mellon of the University of Colorado, Boulder, said. "We might expect to see additional changes in the next 20 sols."

Mellon, who has spent most of his career studying permafrost, said long-term monitoring of Snow Queen and other icy soil cleared by Phoenix landing and trenching operations is unprecedented for science. It's the first chance to see visible changes in Martian ice at a place where temperatures are cold enough that the ice doesn't immediately sublimate, or vaporize, away. Phoenix scientists discovered that centimeter-sized chunks of ice scraped up in the Dodo-Goldilocks trench lasted several days before vanishing.

The Phoenix team has been watching ice in the Dodo-Goldilocks and Snow White trenches in views from the lander's Surface Stereo Imager as well as RAC, but only RAC can view Snow Queen near a strut under the lander.

The fact that RAC is attached to the robotic arm is both an advantage and a disadvantage. The advantage is that RAC can take close-ups of Snow Queen, while the Surface Stereo Imager can't see Snow Queen at all from the topside of the spacecraft. The disadvantage is that the robotic arm has so many tasks to perform that RAC can't be used for monitoring trench ice at some opportune times. Also, RAC hasn't been used to take up-close images of other icy places under the spacecraft cleared on landing because it would require the robotic arm to make a difficult and complex series of moves.

"I've made a list of hypotheses about what could be forming cracks in Snow Queen, and there are difficulties with all of them," Mellon said.

One possibility is that temperature changes over many sols, or Martian days, have expanded and contracted the surface enough to create stress cracks. It would take a fairly rapid temperature change to form fractures like this in ice, Mellon said.

Another possibility is the exposed layer has undergone a phase change that has caused it to shrink. An example of a phase change could be a hydrated salt losing its water after days of surface exposure, causing the hard layer to shrink and crack. "I don't think that's the best explanation because dehydration of salt would first form a thin rind and finer cracks," Mellon said.

"Another possibility is that these fractures were already there, and they appeared because ice sublimed off the surface and revealed them," he said.

As for the small pebble that popped up on Snow Queen after 21 sols -- it might be a piece that broke free from the original surface or it might be a piece that fell down from somewhere else. "We have to study the shadows a little more to understand what's happening," Mellon said.

The Phoenix mission is led by Smith of the University of Arizona with project management at NASA's Jet Propulsion Laboratory, Pasadena, Calif., and development partnership at Lockheed Martin, Denver. International contributions come from the Canadian Space Agency; the University of Neuchatel; the universities of Copenhagen and Aarhus, Denmark; Max Planck Institute, Germany; and the Finnish Meteorological Institute. For more about Phoenix, visit: http://www.nasa.gov/phoenix and http://phoenix.lpl.arizona.edu.
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Phoenix Scrapes 'Almost Perfect' Icy Soil for Analysis

Phoenix Scrapes 'Almost Perfect' Icy Soil for Analysis
07.01.08

This image shows the trench informally called "Snow White 5," which is Phoenix's current active digging area. NASA's Phoenix Mars Lander enlarged the "Snow White" trench and scraped up little piles of icy soil on Saturday, June 28, the 33rd Martian day, or sol, of the mission. Scientists say that the scrapings are ideal for the lander's analytical instruments. The robotic arm on Phoenix used the blade on its scoop to make 50 scrapes in the icy layer buried under subsurface soil. The robotic arm then heaped the scrapings into a few 10- to 20-cubic centimeter piles, or piles each containing between two and four teaspoonfuls. Scraping created a grid about two millimeters deep. The scientists saw the scrapings in Surface Stereo Imager images on Sunday, June 29, agreed they had "almost perfect samples of the interface of ice and soil," and commanded the robotic arm to pick up some scrapings for instrument analysis. The scoop will sprinkle the fairly fine-grained material first onto the Thermal and Evolved-Gas Analyzer (TEGA). The instrument has tiny ovens to bake and sniff the soil to assess its volatile ingredients, such as water. It can determine the melting point of ice. Phoenix's overall goals are to: dig to water frozen under subsurface soil, touch, examine, vaporize and sniff the soil and ice to discover the history of water on Mars, determine if the Martian arctic soil could support life, and study Martian weather from a polar perspective. The Phoenix mission is led by Peter Smith of The University of Arizona with project management at JPL and development partnership at Lockheed Martin, located in Denver. International contributions come from the Canadian Space Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen and Aarhus, Denmark; Max Planck Institute, Germany; and the Finnish Meteorological Institute. For more information on the Phoenix mission, link to http://www.nasa.gov/mission_pages/phoenix/main/index.html and http://phoenix.lpl.arizona.edu/.