Cassini Spacecraft - Articles - Zimbio

NASA Scientists Exploring Possibility of Life on Saturn's Moon, Enceladus

Mon, 22 Apr 2008 07:09:00 GMT

posted by starling

NASA scientists are exploring the possibility that microbial life exist inside Enceladus, where no sunlight reaches, photosynthesis is impossible and no oxygen is available.

Until the two Voyager spacecraft passed near Enceladus, the sixth-largest moon of Saturn, in the early 1980s, very little was known about this small moon except for the identification of water ice on its surface. The Voyager missions showed that Enceladus is only 500 km in diameter and reflects almost 100% of the sunlight that strikes it. Voyager 1 found that Enceladus orbited in the densest part of Saturn's diffuse E ring, indicating a possible link between the two, while Voyager 2 revealed that despite the moon's small size, it had a wide range of terrains ranging from ancient, heavily cratered surfaces to young, tectonically deformed terrain, with some regions with surface ages as young as 100 million years old.

The Cassini spacecraft performed several close flybys of Enceladus in 2005, revealing the moon's surface and environment in greater detail. In particular, the probe discovered a water-rich plume venting from the moon's south polar region. This discovery, along with the presence of escaping internal heat and very few (if any) impact craters in the south polar region, shows that Enceladus is geologically active today.

Given the level of tectonic resurfacing found on Enceladus, a critical factor in the evolution of life on Earth, has been an important driver of geology on this small moon. Enceladus the fourth body in the solar system to have confirmed volcanic activity, along with Earth, Neptune's Triton, and Jupiter's Io.

There are three ecosystems discovered on Earth that could mirror possible lifeforms on Enceladus. Two are based on methanogens, which belong to an ancient group related to bacteria, called the archaea -- the hardy survivalists of bacteria that thrive in harsh environments without oxygen. Deep volcanic rocks along the Columbia River and in Idaho Falls host two of these ecosystems, which pull their energy from the chemical interaction of different rocks. The third ecosystem is powered by the energy produced in the radioactive decay in rocks, and was found deep below the surface in a mine in South Africa.

NASA's Cassini spacecraft discovered a surprising organic brew erupting in geyser-like fashion from Saturn's moon Enceladus during a close flyby on March 12, 2008. Scientists were stunned that this tiny moon is so active, "hot" and teeming with water vapor and organic chemicals.

"Enceladus has got warmth, water and organic chemicals, some of the essential building blocks needed for life," said Dennis Matson, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We have quite a recipe for life on our hands, but we have yet to find the final ingredient, liquid water, but Enceladus is only whetting our appetites for more."

"A completely unexpected surprise is that the chemistry of Enceladus, what's coming out from inside, resembles that of a comet," said Hunter Waite, principal investigator at the Southwest Research Institute in San Antonio. "To have primordial material coming out from inside a Saturn moon raises many questions on the formation of the Saturn system."

"Enceladus is by no means a comet. Comets have tails and orbit the sun, and Enceladus' activity is powered by internal heat while comet activity is powered by sunlight. Enceladus' brew is like carbonated water with an essence of natural gas," said Waite.

The Casssini Ion and Neutral Mass Spectrometer saw a much higher density of volatile gases, water vapor, carbon dioxide and carbon monoxide, as well as organic materials, some 20 times denser than expected. This dramatic increase in density was evident as the spacecraft flew over the area of the plumes.

New high-resolution heat maps of the south pole by Cassini's Composite Infrared Spectrometer show that the so-called tiger stripes, giant fissures that are the source of the geysers, are warm along almost their entire lengths, and reveal other warm fissures nearby. The warmest regions along the tiger stripes correspond to two of the jet locations seen in Cassini images.

"These spectacular new data will really help us understand what powers the geysers. The surprisingly high temperatures make it more likely that there's liquid water not far below the surface," said John Spencer, Cassini scientist on the Composite Infrared Spectrometer team at the Southwest Research Institute in Boulder, Colo.

Previous ultraviolet observations showed four jet sources, matching the locations of the plumes seen in previous images. This indicates that gas in the plume blasts off the surface into space, blending to form the larger plume.

At closest approach, Cassini was only 30 miles from Enceladus. When it flew through the plumes it was 120 miles from the moon's surface. Cassini's next flyby of Enceladus is in August.

The first step toward answering the question of whether life exists inside the subsurface aquifer of Enceladus is to analyze the organic compounds in the plume. Cassini's March 12 passage through the plume provided some measurements that help us move toward an answer, and preliminary plans call for Cassini to fly through the plume again for more measurements in the future. Ultimately, another mission in the future could conceivably land near the plume or even return plume material to Earth for laboratory analysis.

Organic chemicals were part of the raw material from which Enceladus and Saturn's other moons formed. The origin of Enceladus' heat is less clear, but there are several possibilities that could have given Enceladus a layer of liquid water that persists today. Early on, it could have been heated by decay of short-lived radioactivity in rocks, with the heating prolonged by tidal influences.

Or perhaps an earlier oblong orbit could have brought more tidal heating than exists there today. A past tidal relationship with another moon could have caused the heat. Another theory says the heat could have been produced from a process called serpentization, where chemical binding of water and silicate rock could occur at the upper layer of the moon's core. This increases the volume of the rock and creates energy in the form of heat.

Any of these heating mechanisms might have created a liquid subsurface aquifer solution rich in organics, allowing Enceladus to serve up a suitable prebiotic soup.

The deep sea vent theory for the origin of life on Earth might apply to Enceladus as well. In this scenario, life on Earth began at the interface where chemically rich fluids, heated by tidal or other mechanisms, emerge from below the sea floor. Chemical energy is derived from the reduced gases, such as hydrogen-sulfide and hydrogen coming out from the vent in contact with a suitable oxidant, such as carbon dioxide. Hot spots on an Enceladus sea floor could be locales for this type of process.

We don't know how long it takes for life to start when the ingredients are there and the environment is suitable, but it appears to have happened quickly on Earth. So maybe it was possible that on Enceladus, life started in a "warm little pond" below the icy surface occurring over the last few tens of millions of years.

For life to persist once it has been established requires an environment of liquid water, the essential elements and nutrients, and an energy source. On Enceladus, there is evidence for liquid water, but we don't know its origin. The March 12 close flyby indicates there are some complex organic chemicals, as well. An energy source of some sort is producing geysers. As Cassini's exploration continues, NASA is seeking to bring together more pieces of this intriguing puzzle.

Posted by Casey Kazan. Adapted from materials provided by NASA.

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Saturn's Titan: A Mirror Image of Earth Before Life Evolved?

Tue, 16 Apr 2008 07:08:00 GMT

posted by CaseyKazan

The Cassini spacecraft observations of Saturn's largest moon, the orange-colored Titan, have given scientists a glimpse of what Earth might have been like before life evolved. They now believe Titan possesses many parallels to Earth, including lakes, rivers, channels, dunes, rain, snow, clouds, mountains and possibly volcanoes.

"Titan is just covered in carbon-bearing material -- it's a giant factory of organic chemicals," according to Ralph Lorenz of Johns Hopkins University Applied Physics Laboratory. "We are carbon-based life, and understanding how far along the chain of complexity towards life that chemistry can go in an environment like Titan will be important in understanding the origins of life throughout the universe."

"When we designed the original tour for the Cassini spacecraft, we really did not know what we would find, especially at Enceladus and Titan," said Dennis Matson, the JPL Cassini project scientist. "This extended tour is responding to these new discoveries and giving us a chance to look for more."

Unlike Earth, Titan's lakes, rivers and rain are composed of methane and ethane, and temperatures reach a chilly minus 180 degrees Celsius (minus 290 degrees Fahrenheit). Although Titan's dense atmosphere limits viewing the surface, Cassini's high-resolution radar coverage and imaging by the infrared spectrometer have given scientists a better look.

Titan has hundreds of times more liquid hydrocarbons than all the known oil and natural gas reserves on Earth, according to new data from NASA's Cassini spacecraft. The hydrocarbons rain from the sky, collecting in vast deposits that form lakes and dunes.

At an eye popping minus 179 degrees Celsius (minus 290 degrees Fahrenheit), Titan has a surface of liquid hydrocarbons in the form of methane and ethane with tholins believed to make up its dunes. The term "tholins," coined by Carl Sagan in 1979, describe the complex organic molecules at the heart of prebiotic chemistry.

Cassini has mapped about 20 percent of Titan's surface with radar. Several hundred lakes and seas have been observed, with each of several dozen estimated to contain more hydrocarbon liquid than Earth's oil and gas reserves. Dark dunes that run along the equator contain a volume of organics several hundred times larger than Earth's coal reserves.

Proven reserves of natural gas on Earth total 130 billion tons, enough to provide 300 times the amount of energy the entire United States uses annually for residential heating, cooling and lighting. Dozens of Titan's lakes individually have the equivalent of at least this much energy in the form of methane and ethane.

"This global estimate is based mostly on views of the lakes in the northern polar regions. We have assumed the south might be similar, but we really don't yet know how much liquid is there," said Lorenz. Cassini's radar has observed the south polar region only once, and only two small lakes were visible. Future observations of that area are planned during Cassini's proposed extended mission.

"We also know that some lakes are more than 10 meters or so deep because they appear literally pitch-black to the radar. If they were shallow we'd see the bottom, and we don't," said Lorenz.

The question of how much liquid is on the surface is an important one because methane is a strong greenhouse gas on Titan as well as on Earth, but there is much more of it on Titan. If all the observed liquid on Titan is methane, it would only last a few million years, because as methane escapes into Titan's atmosphere, it breaks down and escapes into space. If the methane were to run out, Titan could become much colder. Scientists believe that methane might be supplied to the atmosphere by venting from the interior in cryovolcanic eruptions. If so, the amount of methane, and the temperature on Titan, may have fluctuated dramatically in Titan's past.

Cassini's mission originally had been scheduled to end in July 2008. A newly-announced two-year extension will include 60 additional orbits of Saturn and more flybys of its exotic moons. These will include 26 flybys of Titan, seven of Enceladus, and one each of Dione, Rhea and Helene. The extension also includes studies of Saturn's rings, its complex magnetosphere, and the planet itself.

"This extension is not only exciting for the science community, but for the world to continue to share in unlocking Saturn's secrets," said Jim Green, director, Planetary Science Division, NASA Headquarters, Washington. "New discoveries are the hallmarks of its success, along with the breathtaking images beamed back to Earth that are simply mesmerizing."

Based on findings from Cassini, scientists think liquid water may be just beneath the surface of Saturn's moon Enceladus. The small moon, only one-tenth the size of Titan and one-seventh the size of Earth's moon, is one of the highest-priority targets for the extended mission.

Cassini discovered geysers of water-ice jetting from the Enceladus surface. The geysers, which shoot out at a distance three times the diameter of Enceladus, feed particles into Saturn's most expansive ring. In the extended mission, the spacecraft may come as close as 25 kilometers (15 miles) from the moon's surface.

Other activities for Cassini scientists will include monitoring seasons on Titan and Saturn, observing unique ring events, such as the 2009 equinox when the sun will be in the plane of the rings, and exploring new places within Saturn's magnetosphere.

Cassini has returned a daily stream of data from Saturn's system for almost four years. Its travel scrapbook includes nearly 140,000 images, and information gathered during 62 revolutions around Saturn, 43 flybys of Titan and 12 close flybys of the icy moons.

More than 10 years after launch and almost four years after entering into orbit around Saturn, Cassini is a healthy and robust spacecraft. Three of its science instruments have minor ailments, but the impact on science-gathering is minimal. The spacecraft will have enough propellant left after the extended mission to potentially allow a third phase of operations. Data from the extended mission could lay the groundwork for possible new missions to Titan and Enceladus.

Cassini launched Oct. 15, 1997, from Cape Canaveral, Fla., on a seven-year journey to Saturn, traversing 3.5 billion kilometers (2.2 billion miles).

Posted by Casey Kazan, adapted from materials provided by NASA.

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Image of the Day

Thu, 25 Apr 2008 22:12:44 GMT

posted by stix1972

Bent Outta Shape

The Prometheus moon steals wispy material from Saturn's F ring, as seen by the Cassini spacecraft.

The irregular Saturnian moon acts as a gravitational tug that pulls away ring dust and debris onto different orbital paths and leaves an uneven pattern of kinks in the F ring. In that way Prometheus appears to live up to its namesake, who stole fire from the Greek Gods and gave it to humans.

The moon's sneaky activity is illuminated by both direct sunlight and reflected light from Saturn, captured by Cassini from 743,000 miles (1.2 kilometers) out. The "saturnshine" often brightens the night sides of Saturn's many moons.

VIDEO: Enceladus, Cold Faithful

IMAGES: Cassini's Latest Discoveries

Special Report: Cassini's Mission to Saturn

— NASA/JPL/Space Science Institute and SPACE.com Staff

Credit: NASA/JPL/Space Science Institute

Return each weekday for a new SPACE.com Image of the Day.

"So Long, and Thanks for All the Fish!" -A Saturn Moon Teaming with Organic Chemicals

Thu, 28 Mar 2008 07:09:00 GMT

posted by CaseyKazan

NASA's Cassini spacecraft discovered a surprising organic brew erupting in geyser-like fashion from Saturn's moon Enceladus during a close flyby on March 12. Scientists are stunned that this tiny moon is so active, "hot" and teeming with water vapor and organic chemicals.

"Enceladus has got warmth, water and organic chemicals, some of the essential building blocks needed for life," said Dennis Matson, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We have quite a recipe for life on our hands, but we have yet to find the final ingredient, liquid water, but Enceladus is only whetting our appetites for more."

Can fish be far behind?

"A completely unexpected surprise is that the chemistry of Enceladus, what's coming out from inside, resembles that of a comet," said Hunter Waite, principal investigator at the Southwest Research Institute in San Antonio. "To have primordial material coming out from inside a Saturn moon raises many questions on the formation of the Saturn system."

"Enceladus is by no means a comet. Comets have tails and orbit the sun, and Enceladus' activity is powered by internal heat while comet activity is powered by sunlight. Enceladus' brew is like carbonated water with an essence of natural gas," said Waite.

The Casssini Ion and Neutral Mass Spectrometer saw a much higher density of volatile gases, water vapor, carbon dioxide and carbon monoxide, as well as organic materials, some 20 times denser than expected. This dramatic increase in density was evident as the spacecraft flew over the area of the plumes.

New high-resolution heat maps of the south pole by Cassini's Composite Infrared Spectrometer show that the so-called tiger stripes, giant fissures that are the source of the geysers, are warm along almost their entire lengths, and reveal other warm fissures nearby. The warmest regions along the tiger stripes correspond to two of the jet locations seen in Cassini images.

"These spectacular new data will really help us understand what powers the geysers. The surprisingly high temperatures make it more likely that there's liquid water not far below the surface," said John Spencer, Cassini scientist on the Composite Infrared Spectrometer team at the Southwest Research Institute in Boulder, Colo.

Previous ultraviolet observations showed four jet sources, matching the locations of the plumes seen in previous images. This indicates that gas in the plume blasts off the surface into space, blending to form the larger plume.

At closest approach, Cassini was only 30 miles from Enceladus. When it flew through the plumes it was 120 miles from the moon's surface. Cassini's next flyby of Enceladus is in August.

The first step toward answering the question of whether life exists inside the subsurface aquifer of Enceladus is to analyze the organic compounds in the plume. Cassini's March 12 passage through the plume provided some measurements that help us move toward an answer, and preliminary plans call for Cassini to fly through the plume again for more measurements in the future. Ultimately, another mission in the future could conceivably land near the plume or even return plume material to Earth for laboratory analysis.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The mission is managed by JPL for NASA's Science Mission Directorate, Washington.

Posted by Casey Kazan.

For images and more information, visit http://www.nasa.gov/cassini or http://saturn.jpl.nasa.gov/ .

A Basic Recipe for Life on Enceladus

Sun, 31 Mar 2008 08:31:25 GMT

posted by nlhouser

“Enceladus has got warmth, water and organic chemicals, some of the essential building blocks needed for life,” Dennis Matson, Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in the statement. “We have quite a recipe for life on our hands, but we have yet to find the final ingredient, liquid water.”

______________________________________________________________ Discovered in 1789 by William Herschel as one of Saturn’s moons, Enceladus is considered as Saturn’s sixth largest moon with very little known about it. At least until NASA’s two 1977 Voyagers, Voyager I and Voyager II–a pair of unmanned scientific probes which were officially designated to study Jupiter and Saturn because of a favorable planetary alignment of the late 70s.

When Cassini was launched in 1997 from Cape Canaveral, Florida, it traveled 2.2 billion miles before it entered orbit in 2004 around Saturn. Today, Cassini is part of a 3.2 billion dollar Cassini-Huygens mission which is a combination mission—NASA, European Space Agency, and the Italian Space Agency.

NASA’s spacecraft Cassini has been able to acquire a lot more information since then which added to the previous Voyager 1’s data—such as there may be a possible connections between the densest part of the E ring of Saturn and its moon, Enceladus—and Voyager’s II date—that the moon had a wide range of terrains ranging from very old to some as young as 100 million years old. The reason that Saturn’s moons are of interest is because the largest moon, Titan, resembles Earth in its earlier days and because in 2005, a significant atmosphere was found.

What is surprising is the latest Cassini findings show that Enceladus has chemical components which resemble that in a comet. This find has caused lots of questions in the scientific community regarding Saturn’s formation. But recently some exciting news has come about Enceladus from the NASA’s Cassini spacecraft, which has revealed a water vapor concentration, with carbon dioxide, carbon monoxide and organ material-all 20 times denser than was ever thought to be, in addition to temperatures being higher than previously.

When Cassini measured temperatures near Enceladus’s south pole, it was minus -135 degrees F., which is 17 degrees warmer than previously taken. “The surprisingly high temperatures make it more likely that there’s liquid water not far below the surface,” John Spencer, another project scientist, said in the statement, e- mailed yesterday.”These spectacular new data will really help us understand what powers the geysers.”