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  • richardmitnick 9:57 am on April 10, 2017 Permalink | Reply
    Tags: , , , , , NASA Cassini,   

    From Many Worlds: “What Scientists Expect to Learn From Cassini’s Upcoming Plunge Into Saturn” 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    Many Worlds

    2017-04-10
    Marc Kaufman

    1
    Saturn as imaged from above by Cassini last year. Over the next five months, the spacecraft will orbit closer and closer to the planet and will finally plunge into its atmosphere. (NASA)

    NASA/ESA/ASI Cassini Spacecraft

    Seldom has the planned end of a NASA mission brought so much expectation and scientific high drama.

    The Cassini mission to Saturn has already been a huge success, sending back iconic images and breakthrough science of the planet and its system. Included in the haul have been the discovery of plumes of water vapor spurting from the moon Encedalus and the detection of liquid methane seas on Titan. But as members of the Cassini science team tell it, the end of the 13-year mission at Saturn may well be its most scientifically productive time.

    Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL) put it this way: “Cassini will make some of its most extraordinary observations at the end of its long life.”

    This news was first announced last week, but I thought it would be useful to go back to the story to learn more about what “extraordinary” science might be coming our way, with the help of Spilker and NASA headquarters Cassini program scientist Curt Niebur.

    And the very up close encounters with Saturn’s rings and its upper atmosphere — where Cassini is expected to ultimately lose contact with Earth — certainly do offer a trove of scientific riches about the basic composition and workings of the planet, as well as the long-debated age and origin of the rings. What’s more, everything we learn about Saturn will have implications for, and offer insights into, the vast menagerie of gas giant exoplanets out there.

    “The science potential here is just huge,” Niebur told me. “I could easily conceive of a billion dollar mission for the science we’ll get from the grand finale alone.”

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    The Cassini spacecraft will make 22 increasingly tight orbits of Saturn before it disappears into the planet’s atmosphere in mid-September, as shown in this artist rendering. (NASA/JPL-Caltech)

    The 20-year, $3.26 billion Cassini mission, a collaboration of NASA, the European Space Agency and the Italian Space Agency, is coming to an end because the spacecraft will soon run out of fuel. The agency could have just waited for that moment and let the spacecraft drift off into space, but decided instead on the taking the big plunge.

    This was considered a better choice not only because of those expected scientific returns, but also because letting the dead spacecraft drift meant that theoretically it could be pulled towards Titan or Enceladus — moons that researchers now believe just might support life.

    Although the spacecraft was sterilized before launch, scientists didn’t want to take the chance that some bacteria might remain in the capsule that could possibly contaminate the moons with life from Earth.

    So instead Cassini will be sent on 22 closer and closer passes around Saturn, into the region between the innermost ring and the atmosphere where no spacecraft has ever gone. On April 26, Cassini will make the first of those dives through a 1,500-mile-wide gap between Saturn and its rings as part of the mission’s grand finale.

    As it makes those terminal orbits, the spacecraft will have to be maneuvered with precision so it doesn’t actually fly into one of the rings. They consist of water ice, small meteorites and dust, and are sufficiently dense to fatally damage Cassini.

    “Based on our best models, we expect the gap to be clear of particles large enough to damage the spacecraft. But we’re also being cautious by using our large antenna as a shield on the first pass, as we determine whether it’s safe to expose the science instruments to that environment on future passes,” said Earl Maize, Cassini project manager at the NASA Jet Propulsion Lab. “Certainly there are some unknowns, but that’s one of the reasons we’re doing this kind of daring exploration at the end of the mission.”

    Then in mid-September, following a distant encounter with Titan and its gravity, the spacecraft’s path will be bent so that it dives into the planet itself. The final descent will occur in mid September, when Cassini enters the atmosphere where it will soon begin to spin and tumble, lose radio contact with Earth, and then ultimately explode due to pressures created by the enormous planet.

    All the while it will be taking pioneering measurements, and sending back images predicted to be spectacular.

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    The age and origin of the rings of Saturn remains a subject of a great debate that may soon come to an end. Ring particle sizes range from tiny, dust-sized icy grains to a few particles as large as mountains. Two tiny moons orbit in gaps (Encke and Keeler gaps) in the rings and keep the gaps open. (NASA)

    While the Cassini team has to keep clear of the rings, the spacecraft is expected to get close enough to most likely answer one of the most long-debated questions about Saturn: how old are those grand features, unique in our solar system?

    One school of thought says they date from the earliest formation of the planet, some 4.6 billion years ago. In other words, they’ve been there as long as the planet has been there.

    But another school says they are a potentially much newer addition. They could potentially be the result of the break-up of a moon (of which Saturn has 53-plus) or a comet, or perhaps of several moons at different times. In this scenario, Saturn may have been ring-less for eons.

    As Niebur explained it, the key to dating the rings is a close view of, essentially, how dirty they are. Because small meteorites and dust are a ubiquitous feature of space, the rings would have significantly more mass if they have been there 4.6 billion years. But if they are determined to be relatively clean, then the age is likely younger, and perhaps much younger.

    “Space is a very dirty place, with dust and micro-meteorites hitting everything. Over significant time scales this stuff coats things. So if the rings the rings are old, we should find very dirty ice. If there is little covering of the ice, then the rings must be young. We may well be coming to the end of a great debate.”

    A corollary of the question of the age of Saturn’s rings is, naturally, how stable they are.

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    Curt Neibur, lead program scientist at NASA headquarters for the Cassini mission. (NASA)

    If they turn out to be as old as the planet, then they are certainly very stable. But if they are not old, then it is entirely plausible that they could be a passing phenomenon and will some day disappear — to perhaps re-appear after another moon is shattered or comet arrives.

    Another way of looking at the rings is that they may well have been formed at different times.

    As Spilker explained in an email, Cassini’s measurements of the mass of the rings will be key. “More massive rings could be as old as Saturn itself while less massive rings must be young. Perhaps a moon or comet got too close and was torn apart by Saturn’s gravity.”

    The voyage between the rings will also potentially provide some new insights into the workings of the disks present at the formation of all solar systems.

    “The rings can teach us about the physics of disks, which are huge rings floating majestically and with synchronicity around the new sun,” Niebur said. “That said, the rings of Saturn have a very active regime, with particles and meteorites and micrometeorites smacking into each other. It’s an amazing environment and has direct relevance to the nebular model of planetary formation.”

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    This recently released Cassini image show’s moon Daphnis, which is embedded within a ring. The moon
    kicks up waves as it orbits within what is called the Keeler gap. This mosaic combines several previous images to show more waves in the gap edges. (NASA/JPL-Caltech)

    Another open question that scientists hope will be answered during the plunge is how long, precisely, is a day on Saturn.

    The saturnine day is often given as between 10.5 and 11 hours, but that lack of precision is unique in our solar system.

    The usual way to determine a planet’s rotation is to look for a distinctive point and watch to see how long it takes to reappear. But Saturn has thousands of miles of thick clouds between the rings and the core, and so no distinctive points have been found.

    The planet’s inner rocky core and outer core of metallic hydrogen create magnetic fields that potentially could be traced to measure a full rotation. But competing magnetic fields in the complex Saturn ring and moon system make that also difficult.

    “The truth is that we don’t know how long a day is on Saturn,” Niebur said. “But after the finale, we will finally know.”

    The answer will hopefully come by measuring the expected “wobble” of the magnetic field inside the rings. Since Cassini will pass beyond the magnetic interference of those rings, the probe should get the most precise magnetic readings ever taken.

    Project scientist Spilker is optimistic. “With the magnetic field we’ll be able to get, for the first time, the length of day for the interior of Saturn. If there’s just a slight tilt to the magnetic field, then it will wobble around and give us the length of a day.”

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    Artist rendering of Cassini over Saturn’s north pole, with it huge hexagon-shaped storm. (NASA/JPL-Caltech)

    Perhaps the most consequential findings to come out of the Cassini finale are expected to involve the planet’s internal structure and composition.

    The atmosphere is known to contain hydrogen, helium, ammonia and methane, but Niebur said that other important trace elements are expected to be present. The probe will use its mass spectrometer to “taste” the chemistry of the gases on the outermost edge of Saturn’s atmosphere and return the most detailed information ever about Saturn’s high-altitude clouds, as well as about the ring material.

    Instruments will also measure Saturn’s powerful winds (which blow up to 1,000 miles an hour), and determine how deep they go in the atmosphere. Like much about Saturn, that basic fact falls in the “unknown” category.

    For both Spilker and Niebur, the biggest prize is probably determining the size and mass of Saturn’s rocky core, made up largely of iron and nickel. That core is estimated to be 9 to 22 times the mass of the Earth, and to have a diameter of perhaps 18,000 miles.

    But these are broad estimates, and neither the size nor mass is really known. Those thousands of miles of thick clouds atop the atmosphere and the planet’s chaotic magnetic fields have made the necessary readings impossible.

    The Cassini instruments, however, are expected to make those measurements during its final months. As Cassini makes its close-in passes and then enters the atmosphere for the final plunge, it will send back the data needed to make detailed maps of Saturn’s inner magnetic and gravitational fields. These are what scientists need to understand the core and other structures that lay beneath the planet’s atmosphere.

    This work will compliment the parallel efforts underway at Jupiter, where the Juno mission is collecting data on that planet’s core as well. If scientists can measure the sizes and masses of both cores, they will be able to use that new information to answer many other questions about our solar system and beyond.

    “A better understanding Saturn’s interior, coupled with what Juno mission learns about the interior of Jupiter, will lead to (new insights into) how the planets in our solar system formed, and how our solar system itself formed,” Spilker said in an email.

    “This is then related to how exoplanets form around other stars. Studying our own giant planets will help us understand giant planets around other stars.”

    In other words, Saturn and Jupiter are planetary types expected to be found across the galaxies. And it’s our good fortune to be able to touch and learn from them, and to use that information to analyze distant planets that we can only indirectly detect or just barely see.

    NASA at Saturn: Cassini’s Grand Finale

    See the full article here .

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    About Many Worlds

    There are many worlds out there waiting to fire your imagination.

    Marc Kaufman is an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer, and is the author of two books on searching for life and planetary habitability. While the “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, any opinions expressed are the author’s alone.

    This site is for everyone interested in the burgeoning field of exoplanet detection and research, from the general public to scientists in the field. It will present columns, news stories and in-depth features, as well as the work of guest writers.

    About NExSS

    The Nexus for Exoplanet System Science (NExSS) is a NASA research coordination network dedicated to the study of planetary habitability. The goals of NExSS are to investigate the diversity of exoplanets and to learn how their history, geology, and climate interact to create the conditions for life. NExSS investigators also strive to put planets into an architectural context — as solar systems built over the eons through dynamical processes and sculpted by stars. Based on our understanding of our own solar system and habitable planet Earth, researchers in the network aim to identify where habitable niches are most likely to occur, which planets are most likely to be habitable. Leveraging current NASA investments in research and missions, NExSS will accelerate the discovery and characterization of other potentially life-bearing worlds in the galaxy, using a systems science approach.
    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 7:54 am on September 28, 2016 Permalink | Reply
    Tags: , , Hidden Wonders, NASA Cassini, , , surrounded by the icy lanes of its rings, The brilliant disk of Saturn   

    From JPL-Caltech: “Hidden Wonders” 

    NASA JPL Banner

    JPL-Caltech

    September 26, 2016
    No writer credit

    1
    No image caption. No image credit.

    NASA’s Cassini spacecraft looks toward the brilliant disk of Saturn, surrounded by the icy lanes of its rings. Faint wisps of cloud are visible in the atmosphere. At bottom, ring shadows trace delicate, curving lines across the planet.

    NASA/ESA/ASI Cassini Spacecraft
    NASA/ESA/ASI Cassini Spacecraft

    Prometheus (53 miles or 86 kilometers across) is just a few pixels wide in this view, barely visible as a dark speck in front of the planet, below the rings and to the left of center.

    Between April and September 2017, Cassini will plunge repeatedly through the gap that separates the planet from the rings.

    This view looks toward the sunlit side of the rings from about a degree above the ring plane. The image was taken in green light with the Cassini spacecraft wide-angle camera on July 21, 2016.

    The view was obtained at a distance of approximately 529,000 miles (852,000 kilometers) from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 37 degrees. Image scale is 30 miles (50 kilometers) per pixel.

    The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

    For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org.

    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 1:30 pm on August 18, 2016 Permalink | Reply
    Tags: , , , ESA's New Norcia station, Most Distant Catch for ESA Station, NASA Cassini   

    From ESA: “Most Distant Catch for ESA Station” 

    ESA Space For Europe Banner

    European Space Agency

    18 August 2016
    No writer credit found

    An ESA tracking station has acquired signals from the international Cassini spacecraft orbiting Saturn, across more than 1.4 billion km of space.

    Following a seven-year journey to Saturn, the NASA/ESA/ASI Cassini orbiter delivered Europe’s Huygens probe to the surface of Saturn’s mysterious moon Titan in January 2005, just a few months after becoming the first spacecraft to enter orbit around the giant gas planet.

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    Cassini crossing rings. In 2016, NASA’s Cassini mission will begin its final ‘Grand Finale’ and ESA’s superbly sensitive deep-space tracking stations will be called in to help gather crucial radio science data.ESA
    18/08/2016

    Since then, Cassini and Huygens have returned a wealth of information on the Saturnian system to the global scientific community, helping us understand the massive planet, its multiple moons and its hauntingly beautiful system of rings.

    Starting later this year, the mission will begin its final phase (see Cassini’s Grand Finale) and ESA’s superbly sensitive deep-space tracking stations will be called in to help gather crucial radio science data.

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    New Norcia station. ESA’s New Norcia station, DSA-1 (Deep Space Antenna-1), hosts a 35 m-diameter parabolic antenna and is located 140 km north of Perth, Western Australia, close to the town of New Norcia. DSA-1 communicates with deep-space missions, typically at ranges in excess of 2 million km. It is also capable of supporting the ultra-precise ‘delta-DOR’ navigation technique. ESA/S. Marti

    In an initial test on 10 August, ESA’s tracking station at New Norcia, Western Australia, hosting a 35 m-diameter, 630-tonne deep-space antenna, received signals transmitted by Cassini through 1.44 billion km of space.

    “This was the farthest-ever reception for an ESA station, and the radio signals – travelling at the speed of light – took 80 minutes to cover this vast distance,” says Daniel Firre, responsible for supporting Cassini radio science at ESOC, ESA’s operations centre in Darmstadt, Germany.

    “We had to upgrade some software at ESOC, as we discovered that one file used for pointing the antenna did not have enough digits to encode the full distance to Cassini, but the test worked and demonstrated we can catch Cassini’s transmissions.”

    Listening Across the Void

    Some types of radio science observations use a ground station to detect signals transmitted from a spacecraft that have reflected off a planet or moon’s surface, or passed through the various layers of its atmosphere – or, in the case of Saturn, its rings.

    Effects on the signals provide valuable information on the composition, state and structure of whatever they have passed through.

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    Tracking stations control room at ESOC

    Numerous missions, including ESA’s Venus Express and Mars Express, have used this technique in the past. All three of ESA’s deep-space tracking stations (New Norcia in Australia, Cebreros in Spain and Malargüe in Argentina) were specifically designed to enable a radio science capability.

    ESA/Venus Express
    ESA/Venus Express

    ESA/Mars Express Orbiter
    ESA/Mars Express Orbiter

    The Cassini mission has performed radio science observations many times during its time at Saturn. Previously, the mission relied solely on the antennas of NASA’s Deep Space Network for these observations.

    Now, the addition of ESA tracking capability will help provide the continuous radio contact needed during Cassini radio science activities. The data received by ESA will be delivered to NASA for subsequent scientific analysis.

    Radio Silence During the Grand Finale

    Starting in December and running into July 2017, Cassini will conduct a daring series of orbits in which the spacecraft will repeatedly climb high above Saturn’s poles, initially passing just outside its narrow F ring, and then later diving between the uppermost atmosphere and the innermost ring.

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    Grand Finale orbits. In 2016, NASA’s Cassini mission will begin its final ‘Grand Finale’ and ESA’s superbly sensitive deep-space tracking stations will be called in to help gather crucial radio science data. NASA/Jet Propulsion Lab

    When Cassini plunges past Saturn, an ESA station will listen, recording radio signals that will be relayed to NASA.

    These data will provide detailed maps of Saturn’s gravity, revealing the planet’s inner composition and possibly helping solve the mystery of just how fast the interior is rotating. They will also help scientists study the rings.

    Until December, a half-dozen more test passes using ESA’s New Norcia and Malargüe stations to receive Cassini signals are planned, after which the two will be used during some two-dozen Grand Finale orbits.

    Inter-Agency Coopration a Key Element

    The support is particularly challenging, as listening passes can last up to 30 hours, during which reception will be handed over multiple times between the two ESA stations and NASA’s Canberra deep-space communication complex in Australia; NASA’s Madrid complex will also take part.

    “We need uninterrupted signal reception to optimise the Cassini radio science data, so the ESA and NASA stations really have to work in close coordination for recording and handover,” says Manfred Lugert, responsible for ESA’s Estrack ground station network.

    Due to geometry, the two ESA stations – located in the southern hemisphere – are ideally able to support Cassini radio science. Northern/southern hemispheric coverage was one factor taken into account when ESA built its station in Argentina in 2012.

    “We are really pleased that we can work closely with our NASA colleagues and contribute to Cassini’s incredibly valuable radio science goals,” says Manfred, adding: “It’s an impressive display of what two agencies working together can achieve.”

    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 6:03 am on July 7, 2016 Permalink | Reply
    Tags: , , , NASA Cassini,   

    From Science Alert: “Saturn’s biggest moon could support a new kind of alien life” 

    ScienceAlert

    Science Alert

    6 JUL 2016
    DAVID NIELD

    1
    Titan. NASA

    When it comes to looking for life on other planets, scientists tend to focus their search on planets that have the right conditions for liquid water to form, but Saturn’s moon Titan might just point the way to the existence of life without water.

    Researchers in the US have been analysing the chemical composition of Saturn’s largest satellite, and think the presence of hydrogen cyanide (HCN) molecules in the atmosphere could pave the way for different forms of life to evolve.

    That’s because HCN reacts to form polymers including polyimine, and polyimine is able to absorb a wide spectrum of light – so wide that it’s enough to capture light penetrating Titan’s dense and hazy atmosphere.

    With that light, the scientists think polyimine could be a possible catalyst for life.

    “Polyimine can exist as different structures, and they may be able to accomplish remarkable things at low temperatures, especially under Titan’s conditions,” said chemist Martin Rahm from Cornell University.

    “We are used to our own conditions here on Earth,” he adds. “Our scientific experience is at room temperature and ambient conditions. Titan is a completely different beast.”

    Titan is Earth-like in that its surface is covered with lakes, rivers, and seas, but these are made up of liquid methane and ethane rather than water. The nitrogen and methane in the air make the planet’s surface too toxic for humans to survive, but the researchers suggest other types of life could prosper.

    The study builds on the Cassini-Huygens missions that have been ongoing for nearly 20 years.

    NASA/ESA/ASI Cassini Spacecraft
    NASA/ESA/ASI Cassini Spacecraft

    ESA Huygens Probe on Cassini
    ESA Huygens Probe on Cassini

    The data collected by the Cassini orbiter and Huygens probe – which landed on Titan back in 2005 – have been invaluable in allowing the Cornell team to simulate a prebiotic chemical trail that could lead to life… but not quite life as we know it.

    The data from the NASA probes was plugged into a computer simulation run by Rahm and his team, which revealed that polyimine could spark life in the ultra-cold temperatures on the surface of Titan. Polyimine’s precursor, hydrogen cyanide, has previously been linked to the start of life on Earth.

    “If future observations could show there is prebiotic chemistry in a place like Titan, it would be a major breakthrough,” said Rahm. “This paper is indicating that prerequisites for processes leading to a different kind of life could exist on Titan, but this [is] only the first step.”

    The research could mean Titan offers two chances of hosting alien life. Scientists think that there is liquid water under the frozen surface of Titan, but locked away in a massive underground ocean – and there’s a lot of speculation that these kinds of underground oceans located throughout the Solar System could hypothetically give rise to life.

    In any case, if the researchers turn out to be right about the polyimine, we can broaden our search for extraterrestrial life beyond planets that very closely match Earth’s environments – and that could be pretty huge.

    Watch this space.

    The findings have been published in Proceedings of the National Academy of Sciences.

    See the full article here .

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  • richardmitnick 2:40 pm on April 14, 2016 Permalink | Reply
    Tags: , , NASA Cassini, , Space dust at Saturn   

    From JPL: “Saturn Spacecraft Samples Interstellar Dust” 

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    JPL-Caltech

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

    Markus Bauer
    European Space Agency, Noordwijk, Netherlands
    011-31-71-565-6799
    markus.bauer@esa.int

    Written by Emily Baldwin, ESA

    1
    Of the millions of dust grains Cassini has sampled at Saturn, a few dozen appear to have come from beyond our solar system. Scientists believe these special grains have interstellar origins because they moved much faster and in different directions compared to dusty material native to Saturn. Image credit: NASA/JPL-Caltech

    NASA/ESA/ASI Cassini Spacecraft
    NASA/ESA/ASI Cassini Spacecraft

    NASA’s Cassini spacecraft has detected the faint but distinct signature of dust coming from beyond our solar system. The research, led by a team of Cassini scientists primarily from Europe, is published this week in the journal Science*.

    Cassini has been in orbit around Saturn since 2004, studying the giant planet, its rings and its moons. The spacecraft has also sampled millions of ice-rich dust grains with its cosmic dust analyzer instrument. The vast majority of the sampled grains originate from active jets that spray from the surface of Saturn’s geologically active moon Enceladus.

    But among the myriad microscopic grains collected by Cassini, a special few — just 36 grains — stand out from the crowd. Scientists conclude these specks of material came from interstellar space — the space between the stars.

    Alien dust in the solar system is not unanticipated. In the 1990s, the ESA/NASA Ulysses mission made the first in-situ observations of this material, which were later confirmed by NASA’s Galileo spacecraft. The dust was traced back to the local interstellar cloud: a nearly empty bubble of gas and dust that our solar system is traveling through with a distinct direction and speed.

    NASA/ESA Ulysses
    NASA/ESA Ulysses

    NASA/Galileo
    NASA/Galileo

    “From that discovery, we always hoped we would be able to detect these interstellar interlopers at Saturn with Cassini. We knew that if we looked in the right direction, we should find them,” said Nicolas Altobelli, Cassini project scientist at ESA (European Space Agency) and lead author of the study. “Indeed, on average, we have captured a few of these dust grains per year, travelling at high speed and on a specific path quite different from that of the usual icy grains we collect around Saturn.”

    The tiny dust grains were speeding through the Saturn system at over 45,000 mph (72,000 kilometers per hour), fast enough to avoid being trapped inside the solar system by the gravity of the sun and its planets.

    “We’re thrilled Cassini could make this detection, given that our instrument was designed primarily to measure dust from within the Saturn system, as well as all the other demands on the spacecraft,” said Marcia Burton, a Cassini fields and particles scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, and a co-author of the paper.

    Importantly, unlike Ulysses and Galileo, Cassini was able to analyze the composition of the dust for the first time, showing it to be made of a very specific mixture of minerals, not ice. The grains all had a surprisingly similar chemical make-up, containing major rock-forming elements like magnesium, silicon, iron and calcium in average cosmic proportions. Conversely, more reactive elements like sulfur and carbon were found to be less abundant compared to their average cosmic abundance.

    “Cosmic dust is produced when stars die, but with the vast range of types of stars in the universe, we naturally expected to encounter a huge range of dust types over the long period of our study,” said Frank Postberg of the University of Heidelberg, a co-author of the paper and co-investigator of Cassini’s dust analyzer.

    Stardust grains are found in some types of meteorites, which have preserved them since the birth of our solar system. They are generally old, pristine and diverse in their composition. But surprisingly, the grains detected by Cassini aren’t like that. They have apparently been made rather uniform through some repetitive processing in the interstellar medium, the researchers said.

    The authors speculate on how this processing of dust might take place: Dust in a star-forming region could be destroyed and recondense multiple times as shock waves from dying stars passed through, resulting in grains like the ones Cassini observed streaming into our solar system.

    “The long duration of the Cassini mission has enabled us to use it like a micrometeorite observatory, providing us privileged access to the contribution of dust from outside our solar system that could not have been obtained in any other way,” said Altobelli.

    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 in Pasadena, manages the mission for NASA’s Science Mission Directorate in Washington. The Cosmic Dust Analyzer is supported by the German Aerospace Center (DLR); the instrument is managed by the University of Stuttgart, Germany.

    For more information about Cassini, visit:

    http://www.nasa.gov/cassini

    http://saturn.jpl.nasa.gov

    *Science paper:
    Flux and composition of interstellar dust at Saturn from Cassini’s Cosmic Dust Analyzer

    Science team:
    N. Altobelli, 1,*,†; F. Postberg, 2,3,†; K. Fiege, 2,4,†;, M. Trieloff, 2,5,†; H. Kimura, 6; V. J. Sterken, 7; H.-W. Hsu, 8; J. Hillier,9; N. Khawaja,3; G. Moragas-Klostermeyer,3; J. Blum, 10;
    M. Burton, 11; R. Srama, 3; S. Kempf, 8; E. Gruen, 2,3,8

    • Author Affiliations

    1 European Space Agency, European Space Astronomy Centre, Madrid, Spain.
    2 Institut für Geowissenschaften, University of Heidelberg, Heidelberg, Germany.
    3 Institut für Raumfahrtsysteme, University of Stuttgart, Stuttgart, Germany.
    4 Georgia Institute of Technology, School of Chemistry and Biochemistry, Atlanta, GA, USA.
    5 Klaus-Tschira-Labor für Kosmochemie, University of Heidelberg, Heidelberg, Germany.
    6 Kobe University, Kobe, Hyōgo, Japan.
    7 International Space Sciences Institute, Bern, Switzerland.
    8 University of Boulder, Boulder, CO, USA.
    9 University of Kent, Kent, UK.
    10 Technische Universität Braunschweig, Institut für Geophysik und Extraterrestrische Physik, Braunschweig, Germany.
    11 Jet Propulsion Laboratory, Pasadena, CA, USA.

    ↵*Corresponding author. E-mail: nicolas.altobelli@sciops.esa.int

    ↵† These authors contributed equally to this work.

    See the full article here .

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    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 10:04 am on August 14, 2015 Permalink | Reply
    Tags: , , NASA Cassini   

    From JPL: “Cassini to Make Last Close Flyby of Saturn Moon Dione” 

    JPL

    August 13, 2015
    Media Contact
    Preston Dyches
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-7013
    preston.dyches@jpl.nasa.gov

    1

    NASA’s Cassini spacecraft will zip past Saturn’s moon Dione on Monday, Aug. 17 — the final close flyby of this icy satellite during the spacecraft’s long mission.

    NASA Cassini Spacecraft
    Cassini

    Cassini’s closest approach, within 295 miles (474 kilometers) of Dione’s surface, will occur at 11:33 a.m. PDT (2:33 p.m. EDT). Mission controllers expect fresh images to begin arriving on Earth within a couple of days following the encounter.

    Cassini scientists have a bevy of investigations planned for Dione. Gravity-science data from the flyby will improve scientists’ knowledge of the moon’s internal structure and allow comparisons to Saturn’s other moons. Cassini has performed this sort of gravity science investigation with only a handful of Saturn’s 62 known moons.

    During the flyby, Cassini’s cameras and spectrometers will get a high-resolution peek at Dione’s north pole at a resolution of only a few feet (or meters). In addition, Cassini’s Composite Infrared Spectrometer instrument will map areas on the icy moon that have unusual thermal anomalies — those regions are especially good at trapping heat. Meanwhile, the mission’s Cosmic Dust Analyzer continues its search for dust particles emitted from Dione.

    This flyby will be the fifth targeted encounter with Dione of Cassini’s tour at Saturn. Targeted encounters require maneuvers to precisely steer the spacecraft toward a desired path above a moon. The spacecraft executed a 12-second burn using its thrusters on Aug. 9, which fine-tuned the trajectory to enable the upcoming encounter.

    Cassini’s closest-ever flyby of Dione was in Dec. 2011, at a distance of 60 miles (100 kilometers). Those previous close Cassini flybys yielded high-resolution views of the bright, wispy terrain on Dione first seen during the Voyager mission. Cassini’s sharp views revealed the bright features to be a system of braided canyons with bright walls. Scientists also have been eager to find out if Dione has geologic activity, like Saturn’s geyser-spouting moon Enceladus, but at a much lower level.

    “Dione has been an enigma, giving hints of active geologic processes, including a transient atmosphere and evidence of ice volcanoes. But we’ve never found the smoking gun. The fifth flyby of Dione will be our last chance,” said Bonnie Buratti, a Cassini science team member at NASA’s Jet Propulsion Laboratory in Pasadena, California.

    Cassini has been orbiting Saturn since 2004. After a series of close moon flybys in late 2015, the spacecraft will depart Saturn’s equatorial plane — where moon flybys occur most frequently — to begin a year-long setup of the mission’s daring final year. For its grand finale, Cassini will repeatedly dive through the space between Saturn and its rings.

    “This will be our last chance to see Dione up close for many years to come,” said Scott Edgington, Cassini mission deputy project scientist at JPL. “Cassini has provided insights into this icy moon’s mysteries, along with a rich data set and a host of new questions for scientists to ponder.”

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

    For more information about Cassini, visit:

    http://www.nasa.gov/cassini

    http://saturn.jpl.nasa.gov

    See the full article here.

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    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 2:46 pm on March 11, 2015 Permalink | Reply
    Tags: , , NASA Cassini,   

    From JPL: “Spacecraft Data Suggest Saturn Moon’s Ocean May Harbor Hydrothermal Activity” 

    JPL

    March 11, 2015
    Preston Dyches
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-7013
    preston.dyches@jpl.nasa.gov

    Dwayne Brown
    NASA Headquarters, Washington
    202-358-1726
    dwayne.c.brown@nasa.gov

    1
    This cutaway view of Saturn’s moon Enceladus is an artist’s rendering that depicts possible hydrothermal activity that may be taking place on and under the seafloor of the moon’s subsurface ocean, based on recently published results from NASA’s Cassini mission. Hydrothermal activity is a process where seawater infiltrates and reacts with a rocky crust, emerging as a heated, mineral-laden solution. This is a natural occurrence in Earth’s oceans. Researchers think microscopic grains of rock detected in the Saturn system by Cassini most likely form when hot water containing dissolved minerals from the moon’s rocky interior travels upward, coming into contact with cooler water. Temperatures required for the interactions that produce the tiny rock grains would be at least 194 degrees Fahrenheit (90 degrees Celsius). On Earth, the most common way to form silica grains of the 6-to-9-nanometer size found by Cassini is hydrothermal activity involving a specific range of conditions. Namely, when slightly alkaline, slightly salty water that is super-saturated with silica undergoes a big drop in temperature. Gravity science measurements from Cassini also suggest Enceladus’ rocky core is quite porous, which would allow water from the ocean to percolate into the interior. This would provide a huge surface area where rock and water could interact. Cassini first revealed active geology on Enceladus in 2005 with evidence of an icy spray issuing from the moon’s south polar region and higher-than-expected temperatures in the icy surface there. With its powerful suite of complementary science instruments, the mission soon revealed a towering plume of water ice and vapor, salts and organic materials that issues from relatively warm fractures on the wrinkled surface. Gravity science results published in 2014 strongly suggested the presence of a 6-mile- (10-kilometer-) deep ocean beneath an ice shell about 19 to 25 miles (30 to 40 kilometers) thick.

    Fast Facts:

    › Cassini finds first evidence of active hot-water chemistry beyond planet Earth
    › Findings in two separate papers support the notion
    › The results have important implications for the habitability of icy worlds

    NASA’s Cassini spacecraft has provided scientists the first clear evidence that Saturn’s moon Enceladus exhibits signs of present-day hydrothermal activity which may resemble that seen in the deep oceans on Earth. The implications of such activity on a world other than our planet open up unprecedented scientific possibilities.

    NASA Cassini Spacecraft
    Cassini

    “These findings add to the possibility that Enceladus, which contains a subsurface ocean and displays remarkable geologic activity, could contain environments suitable for living organisms,” said John Grunsfeld, astronaut and associate administrator of NASA’s Science Mission Directorate in Washington. “The locations in our solar system where extreme environments occur in which life might exist may bring us closer to answering the question: are we alone in the universe.”

    Hydrothermal activity occurs when seawater infiltrates and reacts with a rocky crust and emerges as a heated, mineral-laden solution, a natural occurrence in Earth’s oceans. According to two science papers, the results are the first clear indications an icy moon may have similar ongoing active processes.

    The first paper, published this week in the journal Nature, relates to microscopic grains of rock detected by Cassini in the Saturn system. An extensive, four-year analysis of data from the spacecraft, computer simulations and laboratory experiments led researchers to the conclusion the tiny grains most likely form when hot water containing dissolved minerals from the moon’s rocky interior travels upward, coming into contact with cooler water. Temperatures required for the interactions that produce the tiny rock grains would be at least 194 degrees Fahrenheit (90 degrees Celsius).

    “It’s very exciting that we can use these tiny grains of rock, spewed into space by geysers, to tell us about conditions on — and beneath — the ocean floor of an icy moon,” said the paper’s lead author Sean Hsu, a postdoctoral researcher at the University of Colorado at Boulder.

    Cassini’s cosmic dust analyzer (CDA) instrument repeatedly detected miniscule rock particles rich in silicon, even before Cassini entered Saturn’s orbit in 2004. By process of elimination, the CDA team concluded these particles must be grains of silica, which is found in sand and the mineral quartz on Earth. The consistent size of the grains observed by Cassini, the largest of which were 6 to 9 nanometers, was the clue that told the researchers a specific process likely was responsible.

    On Earth, the most common way to form silica grains of this size is hydrothermal activity under a specific range of conditions; namely, when slightly alkaline and salty water that is super-saturated with silica undergoes a big drop in temperature.

    “We methodically searched for alternate explanations for the nanosilica grains, but every new result pointed to a single, most likely origin,” said co-author Frank Postberg, a Cassini CDA team scientist at Heidelberg University in Germany.

    Hsu and Postberg worked closely with colleagues at the University of Tokyo who performed the detailed laboratory experiments that validated the hydrothermal activity hypothesis. The Japanese team, led by Yasuhito Sekine, verified the conditions under which silica grains form at the same size Cassini detected. The researchers think these conditions may exist on the seafloor of Enceladus, where hot water from the interior meets the relatively cold water at the ocean bottom.

    The extremely small size of the silica particles also suggests they travel upward relatively quickly from their hydrothermal origin to the near-surface sources of the moon’s geysers. From seafloor to outer space, a distance of about 30 miles (50 kilometers), the grains spend a few months to a few years in transit, otherwise they would grow much larger.

    The authors point out that Cassini’s gravity measurements suggest Enceladus’ rocky core is quite porous, which would allow water from the ocean to percolate into the interior. This would provide a huge surface area where rock and water could interact.

    The second paper, recently published in Geophysical Research Letters, suggests hydrothermal activity as one of two likely sources of methane in the plume of gas and ice particles that erupts from the south polar region of Enceladus. The finding is the result of extensive modeling to address why methane, as previously sampled by Cassini, is curiously abundant in the plume.

    The team found that, at the high pressures expected in the moon’s ocean, icy materials called clathrates could form that imprison methane molecules within a crystal structure of water ice. Their models indicate that this process is so efficient at depleting the ocean of methane that the researchers still needed an explanation for its abundance in the plume.

    In one scenario, hydrothermal processes super-saturate the ocean with methane. This could occur if methane is produced faster than it is converted into clathrates. A second possibility is that methane clathrates from the ocean are dragged along into the erupting plumes and release their methane as they rise, like bubbles forming in a popped bottle of champagne.

    The authors agree both scenarios are likely occurring to some degree, but they note that the presence of nanosilica grains, as documented by the other paper, favors the hydrothermal scenario.

    “We didn’t expect that our study of clathrates in the Enceladus ocean would lead us to the idea that methane is actively being produced by hydrothermal processes,” said lead author Alexis Bouquet, a graduate student at the University of Texas at San Antonio. Bouquet worked with co-author Hunter Waite, who leads the Cassini Ion and Neutral Mass Spectrometer (INMS) team at Southwest Research Institute in San Antonio.

    Cassini first revealed active geological processes on Enceladus in 2005 with evidence of an icy spray issuing from the moon’s south polar region and higher-than-expected temperatures in the icy surface there. With its powerful suite of complementary science instruments, the mission soon revealed a towering plume of water ice and vapor, salts and organic materials that issues from relatively warm fractures on the wrinkled surface. Gravity science results published in 2014 strongly suggested the presence of a 6-mile- (10-kilometer-) deep ocean beneath an ice shell about 19 to 25 miles (30 to 40 kilometers) thick.

    The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA’s Jet Propulsion Laboratory in Pasadena, California, manages the mission for the agency’s Science Mission Directorate in Washington. The Cassini CDA instrument was provided by the German Aerospace Center. The instrument team, led by Ralf Srama, is based at the University of Stuttgart in Germany. JPL is a division of the California Institute of Technology in Pasadena.

    More information about Cassini, visit:

    http://www.nasa.gov/cassini

    and

    http://saturn.jpl.nasa.gov

    See the full article here.

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    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 8:09 am on January 9, 2015 Permalink | Reply
    Tags: , , NASA Cassini, NRAO VBLA,   

    From BBC: “Saturn pinpointed to within one mile by giant telescope” 

    BBC
    BBC

    9 January 2015
    Jonathan Webb

    Thanks to a continent-wide radio telescope, astronomers say they know where Saturn is – to within one mile. The calculation is many times more accurate than previous estimations and will be useful for the future study of our solar system and beyond. It used signals sent by the spacecraft Cassini, orbiting Saturn since 2004.

    NASA Cassini Spacecraft
    Cassini

    Ten antennae scattered from Hawaii to the Virgin Islands performed the precise measurement, despite Saturn being nearly a billion miles away.
    This powerful assembly is known as the Very Long Baseline Array (VLBA), a giant telescope in ten parts. The findings were reported at a meeting of the American Astronomical Society in Seattle.

    NRAO VLBA

    “Because of [the VLBA’s] large geographic extent, it has the ability to make very high resolution images – but for this study, the critical thing it can do is measure very precise angles,” explained Dr Dayton Jones of Nasa’s Jet Propulsion Laboratory.

    Dr Jones and his colleagues tracked Cassini’s position relative to a reference grid of quasars – bright, ancient radio wave sources well beyond our galaxy.

    s
    Saturn, pictured by Cassini and now pinpointed in space thanks to the craft’s transmissions

    Without using this type of radio astronomy, where the antennae compare notes in a technique known as “interferometry“, Dr Jones said the best estimates of Saturn’s location were about 20 times less precise.

    From our distant vantage point, predicting Saturn’s trajectory to within about one mile is the equivalent of “the width of a dime at 2,000 miles”, Dr Jones said.

    “This is very good, and far better than previous techniques have been able to provide,” he added, commending the “extraordinary precision” of the VLBA.

    And that precision is especially important when it concerns a giant planet like Saturn.

    “Getting better orbits… particularly for the two planets that dominate the dynamics of our solar system, Jupiter and Saturn, improves the basis of the entire ephemeris,” Dr Jones said.

    Exact model

    An ephemeris is a table of predicted locations in space.

    It has widespread uses in astronomy. Scientists who study the blinking light of pulsars have to be sure of their timing, and require an incredibly exact model of Earth’s own orbit.

    “And all the other bodies in the solar system affect the Earth’s orbit, so you really want to have that all put together in a nice consistent system,” Dr Jones told the BBC.

    Furthermore, when it comes to planning an actual mission there is little room for error.

    “If you want to send a spacecraft to orbit one of the moons of Saturn or Jupiter, you really do want to know what that trajectory has to be, to get there at the same time as the planets do!”

    See the full article here.

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  • richardmitnick 3:16 pm on December 17, 2014 Permalink | Reply
    Tags: , , , , , NASA Cassini   

    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
    Tags: , , , , NASA Cassini,   

    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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