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  • richardmitnick 3:16 pm on December 17, 2014 Permalink | Reply
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    From AAAS: “Spacecraft spots probable waves on Titan’s seas” 

    AAAS

    AAAS

    16 December 2014
    Eric Hand

    It’s springtime on Titan, Saturn’s giant and frigid moon, and the action on its hydrocarbon seas seems to be heating up. Near the moon’s north pole, there is growing evidence for waves on three different seas, scientists reported here today at a meeting of the American Geophysical Union. Researchers are also coming up with the first estimates for the volume and composition of the seas. The bodies appear to be made mostly of methane, and not mostly ethane as previously thought. And they are deep: Ligeia Mare, the second biggest sea with an area larger than Lake Superior, could contain 55 times Earth’s oil reserves.

    l
    Ligeia Mare, shown here in a false-color image from NASA’s Cassini mission, is the second largest known body of liquid on Saturn’s moon Titan. It is filled with liquid hydrocarbons, such as ethane and methane, and is one of the many seas and lakes that bejewel Titan’s north polar region. Cassini has yet to observe waves on Ligeia Mare and will look again during its next encounter on May 23, 2013. The image is a false-color mosaic of synthetic aperture radar images obtained by the Cassini spacecraft between February 2006 and April 2007. Dark areas (low radar return) are colored black while bright regions (high radar return) are colored yellow to white. In this color scheme, liquids, which are dark to the radar, end up appearing black and the solid surface of Titan, which appears bright to the radar, ends up appearing yellow.

    NASA Cassini Spacecraft
    NASA/Cassini

    The evidence is coming from NASA’s Cassini spacecraft, which has being exploring the Saturn system since 2004. In 2009, the northern hemisphere of Titan passed its spring equinox, when it begins tilting toward the sun, and climate models predicted that the increased light would kick up winds as the moon approaches summer in 2017.

    That appears to be happening. In a handful of flybys of Titan in the past 6 months, Cassini scientists have seen signs of waves on three different seas: Kraken Mare, Ligeia Mare, and Punga Mare. Some of the evidence is based on radar reflections, which detect roughness at the sea surface. Particularly intriguing has been a feature on Ligeia Mare dubbed the Magic Island because it appeared, disappeared, and reappeared over the past 2 years. Jason Hofgartner, a planetary science graduate student at Cornell University, says that a likely explanation is transient episodes of waves. “It is neither magical nor an island. But the name has stuck,” he says.

    k
    This is a segment of a colorized mosaic from NASA’s Cassini mission that shows the most complete view yet of Titan’s northern land of lakes and seas. Saturn’s moon Titan is the only world in our solar system other than Earth that has stable liquid on its surface. The liquid in Titan’s lakes and seas is mostly methane and ethane. Seas and major lakes are labeled in the annotated version. The data were obtained by Cassini’s radar instrument from 2004 to 2013. In this color scheme, liquids appear blue and black depending on the way the radar bounced off the surface. Land areas appear yellow to white. Kraken Mare, Titan’s largest sea, is the body in black and blue that sprawls from just below and to the right of the north pole down to the bottom. Most of the bodies of liquid on Titan occur in the northern hemisphere. In fact nearly all the lakes and seas on Titan fall into a box covering about 600 by 1,100 miles (900 by 1,800 kilometers). Only 3 percent of the liquid at Titan falls outside of this area. Scientists are trying to identify the geologic processes that are creating large depressions capable of holding major seas in this limited area. A prime suspect is regional extension of the crust, which on Earth leads to the formation of faults creating alternating basins and roughly parallel mountain ranges. This process has shaped the Basin and Range province of the western United States, and during the period of cooler climate 13,000 years ago much of the present state of Nevada was flooded with Lake Lahontan, which (though smaller) bears a strong resemblance to the region of closely packed seas on Titan.

    p
    This is a segment of a colorized mosaic from NASA’s Cassini mission that shows the most complete view yet of Titan’s northern land of lakes and seas. Saturn’s moon Titan is the only world in our solar system other than Earth that has stable liquid on its surface. The liquid in Titan’s lakes and seas is mostly methane and ethane. The data were obtained by Cassini’s radar instrument from 2004 to 2013. In this color scheme, liquids appear blue and black depending on the way the radar bounced off the surface. Land areas appear yellow to white. Punga Mare is just below the north pole.
    Most of the bodies of liquid on Titan occur in the northern hemisphere. In fact nearly all the lakes and seas on Titan fall into a box covering about 600 by 1,100 miles (900 by 1,800 kilometers). Only 3 percent of the liquid at Titan falls outside of this area.

    Scientists involved in the discoveries have been cautious, saying that the features could also be floating debris or bubbles. At Kraken Mare, however, Cassini researchers detected a wavelike feature with both the spacecraft’s radar and a mapping spectrometer. That double detection gives Alexander Hayes, a planetary scientist at Cornell, extra confidence. “It’s most likely waves,” Hayes says. He calculates that the waves are moving at about 0.7 meters per second and at heights of about 1.5 centimeters. “They’re not huge,” he says. Right now, Hayes says, the waves seem to be appearing only in scattered patches where islands or canyons could be funneling winds—a phenomenon that sailors call cat’s paws. In January, Cassini will make another flyby of Titan that will allow the spectrometer a chance to confirm a radar feature detected in Punga Mare.

    NASA
    Chief Scientist Ellen Stofan, who has spent much of her career studying Titan, calls the results a “vindication” for those who predicted seasonal change. “To me, it’s exciting,” she says. “It says that Titan is a dynamic place.” She says that Cassini scientists can now look for evidence that the waves, now or in the past, have eroded into the jagged, frozen shorelines and created long, straight beaches—features that have been mostly lacking in Cassini data.

    Other scientists at the meeting reported on using Cassini’s radar to assess the size and contents of the seas. The maximum depth of Kraken Mare appears to be 160 meters, and Ligeia Mare could be as much as 200 meters deep, reported Marco Mastrogiuseppe of Sapienza University of Rome. The fact that the radar signals could bounce off the sea bottom suggests that the seas were more transparent than expected and thus must contain mostly methane, not ethane. Hayes says his best estimate is about 90% methane. Essam Marouf, a planetary scientist at San José State University in California, reported on the first results from a separate radar experiment that sent radar reflections to Earth instead of back to the spacecraft. Those tests provide independent evidence that the seas are dominated by methane, Marouf says, and it implies that the lakes are kept filled by precipitating methane.

    Decades ago, planetary scientists such as David Stevenson of the California Institute of Technology in Pasadena had predicted that the seas might be mostly ethane. “It certainly wasn’t obvious that they would be methane-dominated,” Stevenson says. Part of the reason for that presupposition is that light coverts methane in the atmosphere to ethane. Over billions of years, this process would deplete Titan’s surface stores of methane unless it was kept resupplied by a reservoir. Some scientists have proposed that erupting cryovolcanoes or deep underground aquifers of liquid methane occasionally recharge Titan with methane. “There is an unsolved question underlying this,” Stevenson says. “Where does all the methane come from?”

    *Correction, 17 December, 11 a.m.: This item originally used the phrase “bodies of water” to describe methane seas. We have struck the words “of water.”

    See the full article here.

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  • richardmitnick 2:02 pm on December 10, 2014 Permalink | Reply
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    From JPL- “Saturn’s Moons: What a Difference a Decade Makes “ 

    JPL

    December 9, 2014
    Preston Dyches
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-7013
    preston.dyches@jpl.nasa.gov

    Almost immediately after NASA’s twin Voyager spacecraft made their brief visits to Saturn in the early 1980s, scientists were hungry for more. The Voyagers had offered them only a brief glimpse of a family of new worlds — Saturn’s icy moons — and the researchers were eager to spend more time among those bodies.

    NASA Voyager 1
    NASA/Voyager 1

    NASA Voyager 2
    NASA/Voyager 2

    The successor to the Voyagers at Saturn, NASA’s Cassini spacecraft, has spent the past 10 years collecting images and other data as it has toured the Ringed Planet and its family of satellites. New color maps, produced from this trove of data, show that Cassini has essentially fulfilled one of its many mission objectives: producing global maps of Saturn’s six major icy moons.

    NASA Cassini Spacecraft
    NASA/Cassini

    These are the large Saturnian moons, excluding haze-covered Titan, known before the start of the Space Age: Mimas, Enceladus, Tethys, Dione, Rhea and Iapetus. Aside from a gap in the north polar region of Enceladus (to be filled in next year), and some areas of Iapetus, this objective is now more or less complete.

    Before (Voyager)
    m

    After (Cassini)
    a
    Mimas

    Before (Voyager)
    e
    After (Cassini)
    a
    Enceladus.

    Before (Voyager)
    t
    After (Cassini)
    k
    Tethys

    Before (Voyager)
    d
    After (Cassini)
    s
    Dione

    Before (Voyager)
    r
    After (Cassini)
    r
    Rhea

    Before (Voyager)
    l
    After (Cassini)
    j
    Iapetus

    All maps Image Credit: NASA/JPL-Caltech/SSI/LPI

    The new maps are the best global, color maps of these moons to date, and the first to show natural brightness variations and high-resolution color together. Colors in the maps represent a broader range than human vision, extending slightly into infrared and ultraviolet wavelengths. Differences in color across the moons’ surfaces that are subtle in natural-color views become much easier to study in these enhanced colors.

    Cassini’s enhanced color views have yielded several important discoveries about the icy moons. The most obvious are differences in color and brightness between the two hemispheres of Tethys, Dione and Rhea. The dark reddish colors on the moons’ trailing hemispheres are due to alteration by charged particles and radiation in Saturn’s magnetosphere. Except for Mimas and Iapetus, the blander leading hemispheres of these moons — that is, the sides that always face forward as the moons orbit Saturn — are all coated with icy dust from Saturn’s E-ring, formed from tiny particles erupting from the south pole of Enceladus.

    Enceladus itself displays a variety of colorful features. Some of the gas and dust being vented into space from large fractures near the moon’s south pole returns to the surface and paints Enceladus with a fresh coating. The yellow and magenta tones in Cassini’s color map are thought to be due to differences in the thickness of these deposits. Many of the most recently formed fractures on Enceladus, those near the south pole in particular, have a stronger ultraviolet signature, which appears bluish in these maps. Their color may be due to large-grained ice exposed on the surface, not unlike blue ice seen in some places in Earth’s Arctic.

    The new maps were produced by Paul Schenk, a participating scientist with the Cassini imaging team based at the Lunar and Planetary Institute in Houston.

    The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory in Pasadena, California, manages the Cassini and Voyager missions for NASA’s Science Mission Directorate in Washington. The two Voyager spacecraft and the Cassini orbiter, along with its two onboard cameras, were designed, developed and assembled at JPL. The Cassini imaging team consists of scientists from the United States, England, France and Germany. The imaging team is based at the Space Science Institute in Boulder, Colorado.

    More information about Cassini is available at the following sites:

    http://www.nasa.gov/cassini

    http://saturn.jpl.nasa.gov

    See the full article here.

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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  • richardmitnick 6:18 am on December 8, 2014 Permalink | Reply
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    From ESA: “Cassini’s view of Jupiter’s southern hemisphere” 

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    European Space Agency

    08/12/2014

    This Cassini image shows Jupiter from an unusual perspective. If you were to float just beneath the giant planet and look directly up, you would be greeted with this striking sight: red, bronze and white bands encircling a hazy south pole. The multicoloured concentric layers are broken in places by prominent weather systems such as Jupiter’s famous Great Red Spot, visible towards the upper left, chaotic patches of cloud and pale white dots. Many of these lighter patches contain lightning-filled thunderstorms.

    j

    NASA Cassini Spacecraft
    NASA/Cassini

    Jupiter has very dramatic weather – the planet’s axis is not as tilted (towards or away from the Sun) as much as Earth’s so it does not have significant seasonal changes, but it does have a thick and tumultuous atmosphere filled with raging storms and chaotic cloud systems.

    These clouds, formed from dense layers of ammonia crystals, are tugged, stretched and tangled together by Jupiter’s turbulence and strong winds, creating vortices and hurricane-like storms with wind speeds of up to 360 km per hour.

    The Great Red Spot is actually an anticyclone that has been violently churning for hundreds of years. It was at one stage large enough to contain several Earth-sized planets but recent images from the Hubble Space Telescope show it to be shrinking. There are other similarly striking storms raging in both Jupiter’s cool upper atmosphere and hotter lower layers, including a Great Dark Spot and Oval BA, more affectionately nicknamed Red Spot Jr.

    Jupiter’s south pole is at the very centre of this image, visible as a murky grey-toned circle. This patch is not as detailed as the rest of the planet because Cassini had to peer through a lot more atmospheric haze in the polar region, making it harder to see.

    This polar map is composed of 18 colour images taken by the narrow-angle camera on NASA’s Cassini spacecraft during a flyby on 11–12 December 2000. This map is incredibly detailed; the smallest visible features in this image are about 120 km across. There is also an accompanying map of the planet’s north pole. In 2016, NASA’s Juno spacecraft will arrive at Jupiter and start to beam back images of the planet’s poles.

    The Cassini–Huygens mission, launched in 1997 as a joint endeavour of ESA, NASA and Italy’s ASI space agency, flew past Venus, Earth and Jupiter en route to observe Saturn, its moons and rings. Observations with Cassini have given us an unprecedented understanding of the Saturnian system. ESA’s Juice mission aims to do the same for Jupiter. Planned for launch in 2022, the spacecraft will reach Jupiter in 2030 and begin observing the planet and three of its moons – Ganymede, Callisto and Europa. Previous flybys of these moons have raised the exciting prospect that some of them might harbour subsurface liquid oceans and conditions suitable to support some forms of life.

    Juice was recently given the green light to continue to the next stage of development.

    ESA JUICE

    See the full article here.

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 9:48 am on November 11, 2014 Permalink | Reply
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    From NASA/Cassini: “Cassini Sails into New Ocean Adventures on Titan” 

    NASA Cassini Spacecraft

    Cassini-Huygens

    November 10, 2014
    Preston Dyches
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-7013
    preston.dyches@jpl.nasa.gov

    NASA’s Cassini mission continues its adventures in extraterrestrial oceanography with new findings about the hydrocarbon seas on Saturn’s moon Titan. During a flyby in August, the spacecraft sounded the depths near the mouth of a flooded river valley and observed new, bright features in the seas that might be related to the mysterious feature that researchers dubbed the “magic island.”

    The findings are being presented this week at the Division for Planetary Sciences Meeting of the American Astronomical Society held in Tucson, Arizona.

    To the delight of Cassini scientists, two new bright features appeared in Titan’s largest sea, Kraken Mare, during the August 21 flyby. In contrast to a previously reported bright, mystery feature in another of Titan’s large seas, Ligeia Mare, the new features in Kraken Mare were observed in both radar data and images from Cassini’s Visible and Infrared Mapping Spectrometer (VIMS). Having observations at two different wavelengths provides researchers with important clues to the nature of these enigmatic objects.

    km
    False-color mosaic of synthetic aperture radar images showing all of Kraken Mare. The large island Mayda Insula is left of top center, and Jingpo Lacus is at upper left. A portion of Ligeia Mare enters the view at top right.

    lm
    Ligeia Mare from a false-color mosaic of synthetic aperture radar images of Titan’s north polar region.

    The VIMS data suggest the new features might have similarities to places in and around the seas that the Cassini team has interpreted as waves or wet ground. The observations support two of the possible explanations the team thinks are most likely — that the features might be waves or floating debris.

    Unfortunately for mystery lovers, the August Titan flyby marked the final opportunity for Cassini’s radar to observe Kraken Mare. However, the spacecraft is scheduled to observe the original “magic island” feature in Ligeia Mare once more, in January 2015.

    The August Titan flyby also included a segment designed to collect altimetry (or height) data, using the spacecraft’s radar instrument along a 120-mile (200-kilometer) shore-to-shore track of Kraken Mare. For a 25-mile (40-kilometer) segment of this data along the sea’s eastern shoreline, Cassini’s radar beam bounced off the sea bottom and back to the spacecraft, revealing the sea’s depth in that area. This region, which is near the mouth of a large, flooded river valley, showed depths of 66 to 115 feet (20 to 35 meters). Cassini will perform this experiment one last time in January 2015, to try to measure the depth of Punga Mare. Punga Mare is the smallest of three large seas in Titan’s far north, and the only sea whose depth has not been observed by Cassini.

    pm
    Punga Mare from a false-color mosaic of synthetic aperture radar images of Titan’s north polar region. A northern extension of Kraken Mare enters the view at lower right.

    Scientists think that, for the areas in which Cassini did not observe a radar echo from the seafloor, Kraken Mare might be too deep for the radar beam to penetrate. Alternatively, the signal over this region might simply have been absorbed by the liquid, which is mostly methane and ethane. The altimetry data for the area in and around Kraken Mare also showed relatively steep slopes leading down to the sea, which also suggests the Kraken Mare might indeed be quite deep.

    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, Pasadena, manages the mission for NASA’s Science Mission Directorate in Washington. The VIMS team is based at the University of Arizona in Tucson. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the US and several European countries.

    More information about Cassini is available at the following sites:

    http://www.nasa.gov/cassini

    http://saturn.jpl.nasa.gov

    See the full article here.

    Cassini completed its initial four-year mission to explore the Saturn System in June 2008 and the first extended mission, called the Cassini Equinox Mission, in September 2010. Now, the healthy spacecraft is seeking to make exciting new discoveries in a second extended mission called the Cassini Solstice Mission.

    The mission’s extension, which goes through September 2017, is named for the Saturnian summer solstice occurring in May 2017. The northern summer solstice marks the beginning of summer in the northern hemisphere and winter in the southern hemisphere. Since Cassini arrived at Saturn just after the planet’s northern winter solstice, the extension will allow for the first study of a complete seasonal period.

    Cassini launched in October 1997 with the European Space Agency’s Huygens probe. The probe was equipped with six instruments to study Titan, Saturn’s largest moon. It landed on Titan’s surface on Jan. 14, 2005, and returned spectacular results.

    Meanwhile, Cassini’s 12 instruments have returned a daily stream of data from Saturn’s system since arriving at Saturn in 2004.

    Among the most important targets of the mission are the moons Titan and Enceladus, as well as some of Saturn’s other icy moons. Towards the end of the mission, Cassini will make closer studies of the planet and its rings.

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  • richardmitnick 8:17 am on October 24, 2014 Permalink | Reply
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    From SPACE.com:”Saturn’s ‘Death Star’ Moon Mimas Is Weird Inside” 

    space-dot-com logo

    SPACE.com

    October 16, 2014
    Kelly Dickerson

    There’s something strange going on below the surface of Saturn’s Death Star-looking moon Mimas, a new study suggests.

    star

    Mimas’ rotation and its orbit around Saturn make the moon look like it’s rocking and back forth and oscillating similar to the way a pendulum swings. The rocking motion is called libration, and it’s commonly observed in moons that are influenced by the gravity from neighboring planets. However, using images of the moon captured by the Cassini spacecraft, Radwan Tajeddine, a research associate at Cornell University, discovered that the satellite’s libration was much more exaggerated in one spot than predicted. He expects it must be caused by the moon’s weird interior.

    NASA Cassini Spacecraft
    NASA/ Cassini

    “We’re very excited about this measurement because it may indicate much about the satellite’s insides,” Tajeddine said in a statement. “Nature is essentially allowing us to do the same thing that a child does when she shakes a wrapped gift in hopes of figuring out what’s hidden inside.”

    Feel the libration

    Astronomers have long been using the rotation and orbit of celestial bodies to guess what their interiors might be like. Most of the rocking is explained by the interacting forces from Mimas’ rotation and orbit, but one libration was much larger than expected.

    Tajeddine and the team tested five different models of what Mimas might look like below the surface to see which one could explain the exaggerated rocking. They quickly ruled out the possibility that Mimas has a uniform interior, an interior with two different layers or an abnormal mass under the moon’s 88-mile-long (142 kilometers) crater that makes it look like the Death Star from the “Star Wars” franchise.

    However, the last two models could both explain Mimas’ extreme libration. One idea is that the moon has an elongated, oval-shaped core. This elongation might have happened as the moon formed under the push and pull of Saturn’s rings. The teeter tottering could also come from a subsurface ocean, similar to the one on Jupiter’s moon Europa.

    While it’s still a possibility, Tajeddine thinks the subsurface ocean is an unlikely explanation. Astronomers have not observed any evidence of liquid water on Mimas, unlike some of Saturn’s other moons. The heat radiating from the core escapes through the moon’s ice-covered shell and would cause any subsurface ocean that existed to quickly freeze.

    3D Mimas map

    Mimas is the smallest and closest of Saturn’s main eight moons. Its giant crater covers almost one-third of the moon’s icy surface.

    For the past 10 years,the Cassini space probe has been collecting data on Mimas, Saturn and the ringed wonder’s other natural satellites. The Imaging Science Subsystem (ISS) onboard Cassini is a two-camera system that captures ultraviolet and infrared images of Saturn and its moons.

    Tajeddine and a team of researchers sifted through dozens of images captured by ISS and created a 3D map of the moon from the photos to study how Mimas spins and orbits Saturn.

    The new research was published this week in the journal Science.

    See the full article here.

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  • richardmitnick 2:43 pm on October 1, 2014 Permalink | Reply
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    From Cassini: “Swirling Cloud at Titan’s Pole is Cold and Toxic “ 

    NASA Cassini Spacecraft

    Cassini-Huygens

    Scientists analyzing data from NASA’s Cassini mission have discovered that a giant, toxic cloud is hovering over the south pole of Saturn’s largest moon, Titan, after the atmosphere there cooled dramatically.

    titan
    Spectral Map of Titan with Polar Vortex. These two views of Saturn’s moon Titan show the southern polar vortex, a huge, swirling cloud that was first observed by NASA’s Cassini spacecraft in 2012.
    The view at left is a spectral map of Titan obtained with the Cassini Visual and Infrared Mapping Spectrometer (VIMS) on Nov. 29, 2012. The inset image is a natural-color close-up of the polar vortex taken by Cassini’s wide-angle camera.

    vims

    Three distinct components are evident in the VIMS image, represented by different colors: the surface of Titan (orange, near center), atmospheric haze along the limb (light green, at top) and the polar vortex (blue, at lower left).

    To the VIMS instrument, the spectrum of the southern polar vortex shows a remarkable difference with respect to other portions of Titan’s atmosphere: a signature of frozen hydrogen cyanide molecules (HCN). This discovery has suggested to researchers that the atmosphere of Titan’s southern hemisphere is cooling much faster than expected. Observing seasonal shifts like this in the moon’s climate is a major goal for Cassini’s current extended mission.

    The scientists found that this giant polar vortex contains frozen particles of the toxic compound hydrogen cyanide, or HCN.

    “The discovery suggests that the atmosphere of Titan’s southern hemisphere is cooling much faster than we expected,” said Remco de Kok of Leiden Observatory and SRON Netherlands Institute for Space Research, lead author of the study published today in the journal Nature.

    Titan is the only moon in the solar system that is cloaked in a dense atmosphere. Like our home planet, Earth, Titan experiences seasons. As it makes its 29-year orbit around the sun along with Saturn, each season lasts about seven Earth years. The most recent seasonal switch occurred in 2009, when winter gave way to spring in the northern hemisphere, and summer transitioned to autumn in the southern hemisphere.

    In May 2012, while Titan’s southern hemisphere was experiencing autumn, images from Cassini revealed a huge swirling cloud, several hundred miles across, taking shape above Titan’s south pole. This polar vortex appears to be an effect of the change of season.

    A puzzling detail about the swirling cloud is its altitude, some 200 miles (about 300 kilometers) above Titan’s surface, where scientists thought the temperature was too warm for clouds to form. “We really didn’t expect to see such a massive cloud so high in the atmosphere,” said de Kok.

    Keen to understand what could give rise to this mysterious cloud, the scientists dove into Cassini’s observations and found an important clue in the spectrum of sunlight reflected by Titan’s atmosphere.

    A spectrum splits the light from a celestial body into its constituent colors, revealing signatures of the elements and molecules present. Cassini’s visual and infrared mapping spectrometer (VIMS) maps the distribution of chemical compounds in Titan’s atmosphere and on its surface.

    “The light coming from the polar vortex showed a remarkable difference with respect to other portions of Titan’s atmosphere,” says de Kok. “We could clearly see a signature of frozen HCN molecules.”

    As a gas, HCN is present in small amounts in the nitrogen-rich atmosphere of Titan. Finding these molecules in the form of ice was surprising, as HCN can condense to form frozen particles only if the atmospheric temperature is as cold as minus 234 degrees Farenheit (minus 148 degrees Celsius). This is about 200 degrees Fahrenheit (about 100 degrees Celsius) colder than predictions from current theoretical models of Titan’s upper atmosphere.

    To check whether such low temperatures were actually possible, the team looked at observations from Cassini’s composite infrared spectrometer (CIRS), which measures atmospheric temperature at different altitudes. Those data showed that the southern hemisphere of Titan has been cooling rapidly, making it possible to reach the cold temperature needed to form the giant toxic cloud seen on the south pole.

    Atmospheric circulation has been drawing large masses of gas towards the south since the change of season in 2009. As HCN gas becomes more concentrated there, its molecules shine brightly at infrared wavelengths, cooling the surrounding air in the process. Another factor contributing to this cooling is the reduced exposure to sunlight in Titan’s southern hemisphere as winter approaches there.

    “These fascinating results from a body whose seasons are measured in years rather than months provide yet another example of the longevity of the remarkable Cassini spacecraft and its instruments,” said Earl Maize, Cassini project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We look forward to further revelations as we approach summer solstice for the Saturn system in 2017.”

    See the full article here.

    Cassini completed its initial four-year mission to explore the Saturn System in June 2008 and the first extended mission, called the Cassini Equinox Mission, in September 2010. Now, the healthy spacecraft is seeking to make exciting new discoveries in a second extended mission called the Cassini Solstice Mission.

    The mission’s extension, which goes through September 2017, is named for the Saturnian summer solstice occurring in May 2017. The northern summer solstice marks the beginning of summer in the northern hemisphere and winter in the southern hemisphere. Since Cassini arrived at Saturn just after the planet’s northern winter solstice, the extension will allow for the first study of a complete seasonal period.

    Cassini launched in October 1997 with the European Space Agency’s Huygens probe. The probe was equipped with six instruments to study Titan, Saturn’s largest moon. It landed on Titan’s surface on Jan. 14, 2005, and returned spectacular results.

    Meanwhile, Cassini’s 12 instruments have returned a daily stream of data from Saturn’s system since arriving at Saturn in 2004.

    Among the most important targets of the mission are the moons Titan and Enceladus, as well as some of Saturn’s other icy moons. Towards the end of the mission, Cassini will make closer studies of the planet and its rings.

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  • richardmitnick 3:55 pm on September 4, 2014 Permalink | Reply
    Tags: , , , , , , NASA Cassini,   

    From Astrobiology: “Icy Aquifers on Titan Transform Methane Rainfall” 

    Astrobiology Magazine

    Astrobiology Magazine

    The NASA and European Space Agency Cassini mission has revealed hundreds of lakes and seas spread across the north polar region of Saturn’s moon Titan. These lakes are filled not with water but with hydrocarbons, a form of organic compound that is also found naturally on Earth and includes methane. The vast majority of liquid in Titan’s lakes is thought to be replenished by rainfall from clouds in the moon’s atmosphere. But how liquids move and cycle through Titan’s crust and atmosphere is still relatively unknown.

    A recent study led by Olivier Mousis, a Cassini research associate at the University of Franche-Comté, France, examined how Titan’s methane rainfall would interact with icy materials within underground reservoirs. They found that the formation of materials called Clathrate changes the chemical composition of the rainfall runoff that charges these hydrocarbon “aquifers.” This process leads to the formation of reservoirs of propane and ethane that may feed into some rivers and lakes.

    clathrate
    Structure of the 3:1 inclusion complex of urea and 1,6-dichlorohexane. The framework is composed of molecules of urea that are linked by hydrogen bonds, leaving approximately hexagonal channels into which align the molecules of the chlorocarbon. Color scheme: oxygen is red, nitrogen is blue, chlorine is green.

    “We knew that a significant fraction of the lakes on Titan’s surface might possibly be connected with hidden bodies of liquid beneath Titan’s crust, but we just didn’t know how they would interact,” said Mousis. “Now, we have a better idea of what these hidden lakes or oceans could be like.”

    Mousis and colleagues at Cornell University, Ithaca, New York, and NASA’s Jet Propulsion Laboratory, Pasadena, California, modeled how a subsurface reservoir of liquid hydrocarbons would diffuse, or spread, through Titan’s porous, icy crust. They found that, at the bottom of the original reservoir, which contains methane from rainfall, a second reservoir would slowly form. This secondary reservoir would be composed of clathrates.

    cassini
    Cassini

    Clathrates are compounds in which water forms a crystal structure with small cages that trap other substances like methane and ethane. Clathrates that contain methane are found on Earth in some polar and ocean sediments. On Titan, the surface pressure and temperature should allow clathrates to form when liquid hydrocarbons come into contact with water ice, which is a major component of the moon’s crust. These clathrate layers could remain stable as far down as several miles below Titan’s surface.

    One of the peculiar properties of clathrates is that they trap and split molecules into a mix of liquid and solid phases, in a process called fractionation. Titan’s subsurface clathrate reservoirs would interact with and fractionate the liquid methane from the original underground hydrocarbon lake, slowly changing its composition. Eventually the original methane aquifer would be turned into a propane or ethane aquifer.

    “Our study shows that the composition of Titan’s underground liquid reservoirs can change significantly through their interaction with the icy subsurface, provided the reservoirs are cut off from the atmosphere for some period of time,” said Mathieu Choukroun of JPL, one of three co-authors of the study with Mousis.

    Importantly, the chemical transformations taking place underground would affect Titan’s surface. Lakes and rivers fed by springs from propane or ethane subsurface reservoirs would show the same kind of composition, whereas those fed by rainfall would be different and contain a significant fraction of methane. This means researchers could examine the composition of Titan’s surface lakes to learn something about what is happening deep underground, said Mousis.

    The results are published in the Sept. 1, 2014, printed issue of the journal Icarus. The research was funded by the French Centre National d’Etudes Spatiales (CNES) and NASA.

    See the full article here.

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  • richardmitnick 6:11 pm on August 11, 2014 Permalink | Reply
    Tags: , , , , NASA Cassini   

    From NASA/JPL at Caltech: “Cassini Prepares For Its Biggest Remaining Burn” 

    JPL

    August 07, 2014
    Preston Dyches
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-7013
    preston.dyches@jpl.nasa.gov

    NASA’s Cassini spacecraft will execute the largest planned maneuver of the spacecraft’s remaining mission on Saturday, Aug. 9. The maneuver will target Cassini toward an Aug. 21 encounter with Saturn’s largest moon, Titan.

    NASA Cassini Spacecraft
    NASA/Cassini

    The main engine firing will last about a minute and will provide a change in velocity of 41 feet per second (12.5 meters per second). This is the largest maneuver by Cassini in five years. No other remaining maneuver comes close, in the amount of propellant it will consume and the amount by which it will change the spacecraft’s velocity. By contrast, the smallest maneuvers Cassini routinely executes are about 0.4 inches (10 millimeters) per second.

    The large size of the Aug. 9 burn is needed to begin the process of “cranking down” Cassini’s orbit, so that the spacecraft circles Saturn nearer to the plane of the rings and moons. Previously, with each Titan flyby, mission controllers adjusted the spacecraft’s orbit to be increasingly inclined, carrying Cassini high above Saturn’s polar regions. The upcoming maneuver starts reversing that trend, making the orbit increasingly close to the equator.

    Although Cassini has occasionally performed similar large propulsive maneuvers during its decade in the Saturn system, Titan itself has proven to be the workhorse for steering Cassini around Saturn. It is not uncommon for the spacecraft to receive a gravitational assist, or boost, from Titan that rivals or exceeds the 96-minute engine burn Cassini performed in 2004 to insert itself into Saturn orbit.

    The Cassini mission recently celebrated a decade studying Saturn, its rings, moons and magnetosphere.

    The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, Pasadena, California, manages the mission for NASA’s Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology.

    See the full article here.

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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  • richardmitnick 3:36 am on July 3, 2014 Permalink | Reply
    Tags: , , , , NASA Cassini   

    From NASA/Cassini: “Ocean on Saturn Moon Could be as Salty as the Dead Sea “ 

    NASA Cassini Spacecraft

    Cassini-Huygens

    July 2, 2014

    Dwayne Brown
    Headquarters, Washington
    202-354-1726
    dwayne.c.brown@nasa.gov

    Preston Dyches
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-7013
    preston.dyches@jpl.nasa.gov

    Scientists analyzing data from NASA’s Cassini mission have firm evidence the ocean inside Saturn’s largest moon, Titan, might be as salty as the Earth’s Dead Sea.

    titan
    Image Credit: NASA/JPL/SSI/Univ. of Arizona/G. Mitri/University of Nantes

    titan2

    The new results come from a study of gravity and topography data collected during Cassini’s repeated flybys of Titan during the past 10 years. Using the Cassini data, researchers presented a model structure for Titan, resulting in an improved understanding of the structure of the moon’s outer ice shell. The findings are published in this week’s edition of the journal Icarus.

    “Titan continues to prove itself as an endlessly fascinating world, and with our long-lived Cassini spacecraft, we’re unlocking new mysteries as fast as we solve old ones,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, who was not involved in the study.

    Additional findings support previous indications the moon’s icy shell is rigid and in the process of freezing solid. Researchers found that a relatively high density was required for Titan’s ocean in order to explain the gravity data. This indicates the ocean is probably an extremely salty brine of water mixed with dissolved salts likely composed of sulfur, sodium and potassium. The density indicated for this brine would give the ocean a salt content roughly equal to the saltiest bodies of water on Earth.

    “This is an extremely salty ocean by Earth standards,” said the paper’s lead author, Giuseppe Mitri of the University of Nantes in France. “Knowing this may change the way we view this ocean as a possible abode for present-day life, but conditions might have been very different there in the past.”

    Cassini data also indicate the thickness of Titan’s ice crust varies slightly from place to place. The researchers said this can best be explained if the moon’s outer shell is stiff, as would be the case if the ocean were slowly crystalizing, and turning to ice. Otherwise, the moon’s shape would tend to even itself out over time, like warm candle wax. This freezing process would have important implications for the habitability of Titan’s ocean, as it would limit the ability of materials to exchange between the surface and the ocean.

    A further consequence of a rigid ice shell, according to the study, is any outgassing of methane into Titan’s atmosphere must happen at scattered “hot spots” — like the hot spot on Earth that gave rise to the Hawaiian Island chain. Titan’s methane does not appear to result from convection or plate tectonics recycling its ice shell.

    How methane gets into the moon’s atmosphere has long been of great interest to researchers, as molecules of this gas are broken apart by sunlight on short geological timescales. Titan’s present atmosphere contains about five percent methane. This means some process, thought to be geological in nature, must be replenishing the gas. The study indicates that whatever process is responsible, the restoration of Titan’s methane is localized and intermittent.

    “Our work suggests looking for signs of methane outgassing will be difficult with Cassini, and may require a future mission that can find localized methane sources,” said Jonathan Lunine, a scientist on the Cassini mission at Cornell University, Ithaca, New York, and one of the paper’s co-authors. “As on Mars, this is a challenging task.”

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

    See the full article here.

    Cassini completed its initial four-year mission to explore the Saturn System in June 2008 and the first extended mission, called the Cassini Equinox Mission, in September 2010. Now, the healthy spacecraft is seeking to make exciting new discoveries in a second extended mission called the Cassini Solstice Mission.

    The mission’s extension, which goes through September 2017, is named for the Saturnian summer solstice occurring in May 2017. The northern summer solstice marks the beginning of summer in the northern hemisphere and winter in the southern hemisphere. Since Cassini arrived at Saturn just after the planet’s northern winter solstice, the extension will allow for the first study of a complete seasonal period.

    Cassini launched in October 1997 with the European Space Agency’s Huygens probe. The probe was equipped with six instruments to study Titan, Saturn’s largest moon. It landed on Titan’s surface on Jan. 14, 2005, and returned spectacular results.

    Meanwhile, Cassini’s 12 instruments have returned a daily stream of data from Saturn’s system since arriving at Saturn in 2004.

    Among the most important targets of the mission are the moons Titan and Enceladus, as well as some of Saturn’s other icy moons. Towards the end of the mission, Cassini will make closer studies of the planet and its rings.

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  • richardmitnick 7:45 am on June 24, 2014 Permalink | Reply
    Tags: , , , , , NASA Cassini   

    From NASA/JPL at Caltech: “Titan’s Building Blocks Might Pre-date Saturn” 

    JPL

    June 23, 2014
    Preston Dyches/Whitney Clavin
    NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-7013/818-354-4673
    preston.dyches@jpl.nasa.gov/whitney.clavin@jpl.nasa.gov

    A combined NASA and European Space Agency (ESA)-funded study has found firm evidence that nitrogen in the atmosphere of Saturn’s moon Titan originated in conditions similar to the cold birthplace of the most ancient comets from the Oort cloud. The finding rules out the possibility that Titan’s building blocks formed within the warm disk of material thought to have surrounded the infant planet Saturn during its formation.

    titan
    New research on the nitrogen in Titan’s atmosphere indicates that the moon’s raw materials might have been locked up in ices that condensed before Saturn began its formation. Image Credit: NASA/JPL-Caltech/Space Science Institute

    oort
    An artist’s rendering of the Oort cloud and the Kuiper belt (inset). Sizes of individual objects have been exaggerated for visibility.

    The main implication of this new research is that Titan’s building blocks formed early in the solar system’s history, in the cold disk of gas and dust that formed the sun. This was also the birthplace of many comets, which retain a primitive, or largely unchanged, composition today.

    The research, led by Kathleen Mandt of Southwest Research Institute in San Antonio, and including an international team of researchers, was published this week in the Astrophysical Journal Letters.

    Nitrogen is the main ingredient in the atmosphere of Earth, as well as on Titan. The planet-sized moon of Saturn is frequently compared to an early version of Earth, locked in a deep freeze.

    The paper suggests that information about Titan’s original building blocks is still present in the icy moon’s atmosphere, allowing researchers to test different ideas about how the moon might have formed. Mandt and colleagues demonstrate that a particular chemical hint as to the origin of Titan’s nitrogen should be essentially the same today as when this moon formed, up to 4.6 billion years ago. That hint is the ratio of one isotope, or form, of nitrogen, called nitrogen-14, to another isotope, called nitrogen-15.

    The team finds that our solar system is not old enough for this nitrogen isotope ratio to have changed significantly. This is contrary to what scientists commonly have assumed.

    “When we looked closely at how this ratio could evolve with time, we found that it was impossible for it to change significantly. Titan’s atmosphere contains so much nitrogen that no process can significantly modify this tracer even given more than four billion years of solar system history,” Mandt said.

    The small amount of change in this isotope ratio over long time periods makes it possible for researchers to compare Titan’s original building blocks to other solar system objects in search of connections between them.

    As planetary scientists investigate the mystery of how the solar system formed, isotope ratios are one of the most valuable types of clues they are able to collect. In planetary atmospheres and surface materials, the specific amount of one form of an element, like nitrogen, relative to another form of that same element can be a powerful diagnostic tool because it is closely tied to the conditions under which materials form.

    The study also has implications for Earth. It supports the emerging view that ammonia ice from comets is not likely to be the primary source of Earth’s nitrogen. In the past, researchers assumed a connection between comets, Titan and Earth, and supposed the nitrogen isotope ratio in Titan’s original atmosphere was the same as that ratio is on Earth today. Measurements of the nitrogen isotope ratio at Titan by several instruments of the NASA and ESA Cassini-Huygens mission showed that this is not the case — meaning this ratio is different on Titan and Earth — while measurements of the ratio in comets have borne out their connection to Titan. This means the sources of Earth’s and Titan’s nitrogen must have been different.

    Other researchers previously had shown that Earth’s nitrogen isotope ratio likely has not changed significantly since our planet formed.

    “Some have suggested that meteorites brought nitrogen to Earth, or that nitrogen was captured directly from the disk of gas that formed the sun. This is an interesting puzzle for future investigations,” Mandt said.

    Mandt and colleagues are eager to see whether their findings are supported by data from ESA’s Rosetta mission, when it studies comet 67P/ Churyumov-Gerasimenko beginning later this year. If their analysis is correct, the comet should have a lower ratio of two isotopes — in this case of hydrogen in methane ice — than the ratio on Titan. In essence, they believe this chemical ratio on Titan is more similar to Oort cloud comets than comets born in the Kuiper Belt, which begins near the orbit of Neptune (67P/ Churyumov-Gerasimenko is a Kuiper Belt comet).

    ESA Rosetta spacecraft
    ESA/Rosetta

    “This exciting result is a key example of Cassini science informing our knowledge of the history of solar system and how the Earth formed,” said Scott Edgington, Cassini deputy project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California.

    NASA Cassini Spacecraft
    NASA/Cassini

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

    Rosetta is an ESA mission with contributions from its member states and NASA. JPL manages the U.S. contribution of the Rosetta mission for NASA’s Science Mission Directorate in Washington.

    See the full article here.

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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