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  • richardmitnick 8:24 am on May 2, 2014 Permalink | Reply
    Tags: , , , , NASA Galileo,   

    From NASA/JPL at Caltech: “Ganymede May Harbor ‘Club Sandwich’ of Oceans and Ice” 

    NASA/JPL at Caltech

    May 01, 2014
    Whitney Clavin
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-4673
    whitney.clavin@jpl.nasa.gov

    The largest moon in our solar system, a companion to Jupiter named Ganymede, might have ice and oceans stacked up in several layers like a club sandwich, according to new NASA-funded research that models the moon’s makeup.

    gan
    This artist’s concept of Jupiter’s moon Ganymede, the largest moon in the solar system, illustrates the “club sandwich” model of its interior oceans. Image credit: NASA/JPL-Caltech

    Previously, the moon was thought to harbor a thick ocean sandwiched between just two layers of ice, one on top and one on bottom.

    “Ganymede’s ocean might be organized like a Dagwood sandwich,” said Steve Vance of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., explaining the moon’s resemblance to the “Blondie” cartoon character’s multi-tiered sandwiches. The study, led by Vance, provides new theoretical evidence for the team’s “club sandwich” model, first proposed last year. The research appears in the journal Planetary and Space Science.

    The results support the idea that primitive life might have possibly arisen on the icy moon. Scientists say that places where water and rock interact are important for the development of life; for example, it’s possible life began on Earth in bubbling vents on our sea floor. Prior to the new study, Ganymede’s rocky sea bottom was thought to be coated with ice, not liquid — a problem for the emergence of life. The “club sandwich” findings suggest otherwise: the first layer on top of the rocky core might be salty water.

    “This is good news for Ganymede,” said Vance. “Its ocean is huge, with enormous pressures, so it was thought that dense ice had to form at the bottom of the ocean. When we added salts to our models, we came up with liquids dense enough to sink to the sea floor.”

    NASA scientists first suspected an ocean in Ganymede in the 1970s, based on models of the large moon, which is bigger than Mercury. In the 1990s, NASA’s Galileo mission flew by Ganymede, confirming the moon’s ocean, and showing it extends to depths of hundreds of miles. The spacecraft also found evidence for salty seas, likely containing the salt magnesium sulfate.

    NASA Galileo spacecraft
    NASA/Galileo

    Previous models of Ganymede’s oceans assumed that salt didn’t change the properties of liquid very much with pressure. Vance and his team showed, through laboratory experiments, how much salt really increases the density of liquids under the extreme conditions inside Ganymede and similar moons. It may seem strange that salt can make the ocean denser, but you can see for yourself how this works by adding plain old table salt to a glass of water. Rather than increasing in volume, the liquid shrinks and becomes denser. This is because the salt ions attract water molecules.

    The models get more complicated when the different forms of ice are taken into account. The ice that floats in your drinks is called “Ice I.” It’s the least dense form of ice and lighter than water. But at high pressures, like those in crushingly deep oceans like Ganymede’s, the ice crystal structures become more compact. “It’s like finding a better arrangement of shoes in your luggage — the ice molecules become packed together more tightly,” said Vance. The ice can become so dense that it is heavier than water and falls to the bottom of the sea. The densest and heaviest ice thought to persist in Ganymede is called “Ice VI.”

    By modeling these processes using computers, the team came up with an ocean sandwiched between up to three ice layers, in addition to the rocky seafloor. The lightest ice is on top, and the saltiest liquid is heavy enough to sink to the bottom. What’s more, the results demonstrate a possible bizarre phenomenon that causes the oceans to “snow upwards.” As the oceans churn and cold plumes snake around, ice in the uppermost ocean layer, called “Ice III,” could form in the seawater. When ice forms, salts precipitate out. The heavier salts would thus fall downward, and the lighter ice, or “snow,” would float upward. This “snow” melts again before reaching the top of the ocean, possibly leaving slush in the middle of the moon sandwich.

    “We don’t know how long the Dagwood-sandwich structure would exist,” said Christophe Sotin of JPL. “This structure represents a stable state, but various factors could mean the moon doesn’t reach this stable state.

    Sotin and Vance are both members of the Icy Worlds team at JPL, part of the multi-institutional NASA Astrobiology Institute based at the Ames Research Center in Moffett Field, Calif.

    The results can be applied to exoplanets too, planets that circle stars beyond our sun. Some super-Earths, rocky planets more massive than Earth, have been proposed as “water worlds” covered in oceans. Could they have life? Vance and his team think laboratory experiments and more detailed modeling of exotic oceans might help find answers.

    Ganymede is one of five moons in our solar system thought to support vast oceans beneath icy crusts. The other moons are Jupiter’s Europa and Callisto and Saturn’s Titan and Enceladus. The European Space Agency is developing a space mission, called JUpiter ICy moons Explorer or JUICE, to visit Europa, Callisto and Ganymede in the 2030s. NASA and JPL are contributing to three instruments on the mission, which is scheduled to launch in 2022 (see http://www.jpl.nasa.gov/news/news.php?release=2013-069).

    ESA JUICE
    ESA/JUICE

    Other authors of the study are Mathieu Bouffard of Ecole Normale Supérieure de Lyon, France, and Mathieu Choukroun, also of JPL and the Icy World team of the NASA Astrobiology Institute. JPL is managed by the California Institute of Technology in Pasadena for NASA.

    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 10:11 am on February 13, 2014 Permalink | Reply
    Tags: , , , , NASA Galileo, ,   

    From NASA/JPL at Caltech: “Largest Solar System Moon Detailed in Geologic Map” 

    February 12, 2014
    Jia-Rui Cook 818-354-0850
    Jet Propulsion Laboratory, Pasadena,
    Calif. jccook@jpl.nasa.gov

    More than 400 years after its discovery by astronomer Galileo Galilei, the largest moon in the solar system – Jupiter’s moon Ganymede – has finally claimed a spot on the map.

    Ganymede
    To present the best information in a single view of Jupiter’s moon Ganymede, a global image mosaic was assembled, incorporating the best available imagery from NASA’s Voyager 1 and 2 spacecraft and NASA’s Galileo spacecraft. USGS Astrogeology Science Center/Wheaton/NASA/JPL-Caltech

    A group of scientists led by Geoffrey Collins of Wheaton College has produced the first global geologic map of Ganymede, Jupiter’s seventh moon. The map combines the best images obtained during flybys conducted by NASA’s Voyager 1 and 2 spacecraft (1979) and Galileo orbiter (1995 to 2003) and is now published by the U. S. Geological Survey as a global map. It technically illustrates the varied geologic character of Ganymede’s surface and is the first global, geologic map of this icy, outer-planet moon. The geologic map of Ganymede is available for download at: http://www.jpl.nasa.gov/spaceimages/details.php?id=pia17902 ).

    NASA Galileo
    Galileo

    NASA Voyager
    Voyager

    “This map illustrates the incredible variety of geological features on Ganymede and helps to make order from the apparent chaos of its complex surface,” said Robert Pappalardo of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “This map is helping planetary scientists to decipher the evolution of this icy world and will aid in upcoming spacecraft observations.”

    The European Space Agency’s Jupiter Icy Moons Explorer mission is slated to be orbiting Ganymede around 2032. NASA is contributing a U.S.-led instrument and hardware for two European-led instruments for the mission.

    Since its discovery in January 1610, Ganymede has been the focus of repeated observation, first by Earth-based telescopes, and later by the flyby missions and spacecraft orbiting Jupiter. These studies depict a complex, icy world whose surface is characterized by the striking contrast between its two major terrain types: the dark, very old, highly cratered regions, and the lighter, somewhat younger (but still very old) regions marked with an extensive array of grooves and ridges.

    According to the scientists who have constructed this map, three major geologic periods have been identified for Ganymede that involve the dominance of impact cratering, then tectonic upheaval, followed by a decline in geologic activity. The map, which illustrates surface features, such as furrows, grooves and impact craters, allows scientists to decipher distinct geologic time periods for an object in the outer solar system for the first time.

    “The highly detailed, colorful map confirmed a number of outstanding scientific hypotheses regarding Ganymede’s geologic history, and also disproved others,” said Baerbel Lucchitta, scientist emeritus at the U.S. Geological Survey in Flagstaff, Ariz., who has been involved with geologic mapping of Ganymede since 1980. “For example, the more detailed Galileo images showed that cryovolcanism, or the creation of volcanoes that erupt water and ice, is very rare on Ganymede.”

    The Ganymede global geologic map will enable researchers to compare the geologic characters of other icy satellite moons, because almost any type of feature that is found on other icy satellites has a similar feature somewhere on Ganymede.

    “The surface of Ganymede is more than half as large as all the land area on Earth, so there is a wide diversity of locations to choose from,” Collins said. “Ganymede also shows features that are ancient alongside much more recently formed features, adding historical diversity in addition to geographic diversity.”

    Amateur astronomers can observe Ganymede (with binoculars) in the evening sky this month, as Jupiter is in opposition and easily visible.

    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 6:47 am on August 8, 2013 Permalink | Reply
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    From NASA JPL: “If We Landed on Europa, What Would We Want to Know?” 

    [Thanks to @AlexAAutin for tweeting this. I had not seen it. If you do not know of @AlexAAutin, you should check out her blog here.]

    August 07, 2013
    Jia-Rui C. Cook 818-354-0850
    Jet Propulsion Laboratory, Pasadena, Calif.
    jccook@jpl.nasa.gov

    “Most of what scientists know of Jupiter’s moon Europa they have gleaned from a dozen or so close flybys from NASA’s Voyager 2 spacecraft in 1979 and NASA’s Galileo spacecraft in the mid-to-late 1990s. Even in these fleeting, paparazzi-like encounters, scientists have seen a fractured, ice-covered world with tantalizing signs of a liquid water ocean under its surface. Such an environment could potentially be a hospitable home for microbial life. But what if we got to land on Europa’s surface and conduct something along the lines of a more in-depth interview? What would scientists ask? A new study in the journal Astrobiology authored by a NASA-appointed science definition team lays out their consensus on the most important questions to address.

    europa
    Europa’s trailing hemisphere in approximate natural color. The prominent crater in the lower right is Pwyll and the darker regions are areas where Europa’s primarily water ice surface has a higher mineral content. Imaged on 7 September 1996 by Galileo spacecraft.

    ‘If one day humans send a robotic lander to the surface of Europa, we need to know what to look for and what tools it should carry,’ said Robert Pappalardo, the study’s lead author, based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. ‘There is still a lot of preparation that is needed before we could land on Europa, but studies like these will help us focus on the technologies required to get us there, and on the data needed to help us scout out possible landing locations. Europa is the most likely place in our solar system beyond Earth to have life today, and a landed mission would be the best way to search for signs of life.'”

    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 5:58 am on April 13, 2013 Permalink | Reply
    Tags: , , , , NASA Galileo,   

    From JPL at Caltech: “Where are the Best Windows Into Europa’s Interior?” 

    April 12, 2013
    Guy Webster 818-354-6278
    Jet Propulsion Laboratory, Pasadena, Calif.
    guy.webster@jpl.nasa.gov

    The surface of Jupiter’s moon Europa exposes material churned up from inside the moon and also material resulting from matter and energy coming from above. If you want to learn about the deep saltwater ocean beneath this unusual world’s icy shell — as many people do who are interested in possible extraterrestrial life — you might target your investigation of the surface somewhere that has more of the up-from-below stuff and less of the down-from-above stuff.

    moon
    This graphic of Jupiter’s moon Europa maps a relationship between the amount of energy deposited onto the moon from charged-particle bombardment and the chemical contents of ice deposits on the surface in five areas of the moon (labeled A through E). Credit: NASA/JPL-Caltech/Univ. of Ariz./JHUAPL/Univ. of Colo.

    New analysis of observations made more than a decade ago by NASA’s Galileo mission to Jupiter helps identify those places.

    ‘We have found the regions where charged electrons and ions striking the surface would have done the most, and the least, chemical processing of materials emplaced at the surface from the interior ocean,’ said J. Brad Dalton of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., lead author of the report published recently in the journal Planetary and Space Science. ‘That tells us where to look for materials representing the most pristine ocean composition, which would be the best places to target with a lander or study with an orbiter.’

    Europa is about the size of Earth’s moon and, like our moon, keeps the same side toward the planet it orbits. Picture a car driving in circles around a mountain with its left-side windows always facing the mountain.

    Europa’s orbit around Jupiter is filled with charged, energetic particles tied to Jupiter’s powerful magnetic field. Besides electrons, these particles include ions of sulfur and oxygen originating from volcanic eruptions on Io, a neighboring moon.

    The magnetic field carrying these energetic particles sweeps around Jupiter faster than Europa orbits Jupiter, in the same direction: about 10 hours per circuit for the magnetic field versus about 3.6 days for Europa’s orbit. So, instead of our mountain-circling car getting bugs on the front windshield, the bugs are plastered on the back of the car by a “wind” from behind going nearly nine times faster than the car. Europa has a “leading hemisphere” in front and a “trailing hemisphere” in back.

    Earlier studies had found more sulfuric acid being produced toward the center of the trailing hemisphere than elsewhere on Europa’s surface, interpreted as resulting from chemistry driven by sulfur ions bombarding the icy surface.

    Dalton and his co-authors at JPL and at Johns Hopkins University Applied Physics Laboratory, Laurel, Md., examined data from observations by Galileo’s near infrared mapping spectrometer of five widely distributed areas of Europa’s surface. The spectra of reflected light from frozen material on the surface enabled them to distinguish between relatively pristine water and sulfate hydrates. These included magnesium and sodium sulfate salt hydrates, and hydrated sulfuric acid. They compared the distributions of these substances with models of how the influxes of energetic electrons and of sulfur and oxygen ions are distributed around the surface of Europa.

    The concentration of frozen sulfuric acid on the surface varies greatly, they found. It ranges from undetectable levels near the center of the leading hemisphere, to more than half of the surface materials near the center of the heavily bombarded trailing hemisphere. The concentration was closely related to the amount of electrons and sulfur ions striking the surface.

    ‘The close correlation of electron and ion fluxes with the sulfuric acid hydrate concentrations indicates that the surface chemistry is affected by these charged particles,’ says Dalton. ‘If you are interested in the composition and habitability of the interior ocean, the best places to study would be the parts of the leading hemisphere we have identified as receiving the fewest electrons and having the lowest sulfuric acid concentrations.’

    Surface deposits in these areas are most likely to preserve the original chemical compounds that erupted from the interior. Dalton suggests that any future spacecraft missions to Europa should target these deposits for study from orbit, or even attempt to land there.”

    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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