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  • richardmitnick 12:51 pm on January 8, 2019 Permalink | Reply
    Tags: , , , , Io, ,   

    From Southwest Research Institute: “Juno mission captures images of volcanic plumes on Jupiter’s moon Io” 

    SwRI bloc

    From Southwest Research Institute

    Dec. 31, 2018

    A team of space scientists has captured new images of a volcanic plume on Jupiter’s moon Io during the Juno mission’s 17th flyby of the gas giant.

    NASA/Juno

    4
    A volcanic eruption on Io seen by the Galileo spacecraft in 1997. Image via NASA/JPL/DLR.

    On Dec. 21, during winter solstice, four of Juno’s cameras captured images of the Jovian moon Io, the most volcanic body in our solar system.

    2
    Meet Io, Jupiter’s innermost large moon. The red dots – nicknamed the “fires of Io” – are active volcanoes. December 2018 image via NASA’s Juno spacecraft (NASA/JPL-Caltech/SwRI/INAF)

    JunoCam, the Stellar Reference Unit (SRU), the Jovian Infrared Auroral Mapper (JIRAM) and the Ultraviolet Imaging Spectrograph (UVS) observed Io for over an hour, providing a glimpse of the moon’s polar regions as well as evidence of an active eruption.

    “We knew we were breaking new ground with a multi-spectral campaign to view Io’s polar region, but no one expected we would get so lucky as to see an active volcanic plume shooting material off the moon’s surface,” said Scott Bolton, principal investigator of the Juno mission and an associate vice president of Southwest Research Institute’s Space Science and Engineering Division. “This is quite a New Year’s present showing us that Juno has the ability to clearly see plumes.”

    JunoCam acquired the first images on Dec. 21 at 12:00, 12:15 and 12:20 coordinated universal time (UTC) before Io entered Jupiter’s shadow. The Images show the moon half-illuminated with a bright spot seen just beyond the terminator, the day-night boundary.

    “The ground is already in shadow, but the height of the plume allows it to reflect sunlight, much like the way mountaintops or clouds on the Earth continue to be lit after the sun has set,” explained Candice Hansen-Koharcheck, the JunoCam lead from the Planetary Science Institute.

    At 12:40 UTC, after Io had passed into the darkness of total eclipse behind Jupiter, sunlight reflecting off nearby moon Europa helped to illuminate Io and its plume. SRU images released by SwRI depict Io softly illuminated by moonlight from Europa. The brightest feature on Io in the image is thought to be a penetrating radiation signature, a reminder of this satellite’s role in feeding Jupiter’s radiation belts, while other features show the glow of activity from several volcanoes. “As a low-light camera designed to track the stars, the SRU can only observe Io under very dimly lit conditions. Dec. 21 gave us a unique opportunity to observe Io’s volcanic activity with the SRU using only Europa’s moonlight as our lightbulb,” said Heidi Becker, lead of Juno’s Radiation Monitoring Investigation, at NASA’s Jet Propulsion Laboratory.

    Sensing heat at long wavelengths, the JIRAM instrument detects hotspots in the daylight and at night.

    “Though Jupiter’s moons are not JIRAM’s primary objectives, every time we pass close enough to one of them, we take advantage of the opportunity for an observation,” said Alberto Adriani, a researcher at Italy’s National Institute of Astrophysics. “The instrument is sensitive to infrared wavelengths, which are perfect to study the volcanism of Io. This is one of the best images of Io that JIRAM has been able to collect so far.”

    The latest images can lead to new insights into the gas giant’s interactions with its five moons, causing phenomena such as Io’s volcanic activity or freezing of the moon’s atmosphere during eclipse, added Bolton. JIRAM recently documented Io’s volcanic activity before and after eclipse. Io’s volcanoes were discovered by NASA’s Voyager spacecraft in 1979. Io’s gravitational interaction with Jupiter drives the moon’s volcanoes, which emit umbrella-like plumes of SO2 gas and produce extensive basaltic lava fields.

    The recent Io images were captured at the halfway point of the mission, which is scheduled to complete a map of Jupiter in July 2021. Launched in 2011, Juno arrived at Jupiter in 2016. The spacecraft orbits Jupiter every 53 days, studying its auroras, atmosphere and magnetosphere.

    The solar-powered Juno features eight scientific instruments designed to study Jupiter’s interior structure, atmosphere and magnetosphere. NASA’s Jet Propulsion Laboratory manages the Juno mission for Bolton. Juno is part of the New Frontiers Program, which is managed at Marshall Space Flight Center in Huntsville, Alabama, for NASA’s Science Mission Directorate. Lockheed Martin Space built the spacecraft, and SwRI provided two Juno instruments to study the massive Jovian aurora.

    For more information, visit Space Science or contact Robert Crowe, +1 210 522 4630, Communications Department, Southwest Research Institute, PO Drawer 28510, San Antonio, TX 78228-0510.

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    Southwest Research Institute (SwRI) is an independent, nonprofit applied research and development organization. The staff of nearly 2,800 specializes in the creation and transfer of technology in engineering and the physical sciences. SwRI’s technical divisions offer a wide range of technical expertise and services in such areas as engine design and development, emissions certification testing, fuels and lubricants evaluation, chemistry, space science, nondestructive evaluation, automation, mechanical engineering, electronics, and more.

     
  • richardmitnick 12:43 pm on August 29, 2018 Permalink | Reply
    Tags: , , , , , , Io, , Rocky Exomoons   

    From AAS NOVA: “Habitable Moons Instead of Habitable Planets?” 

    AASNOVA

    From AAS NOVA

    29 August 2018
    Susanna Kohler

    1
    Artist’s depiction of an Earth-like exomoon orbiting a gas-giant planet. [NASA/JPL-Caltech]

    One of the primary goals of exoplanet-hunting missions like Kepler is to discover Earth-like planets in their hosts’ habitable zones.

    NASA/Kepler Telescope

    But could there be other relevant worlds to look for? A new study has explored the possibility of habitable moons around giant planets.

    Seeking Rocky Worlds

    Since its launch, the Kepler mission has found hundreds of planet candidates within their hosts’ habitable zones — the regions where liquid water can exist on a planet surface. In the search for livable worlds beyond our solar system, it stands to reason that terrestrial, Earth-like planets are the best targets. But stand-alone planets aren’t the only type of rocky world out there!

    Many of the Kepler planet candidates found to lie in their hosts’ habitable zones are larger than three Earth radii. These giant planets, while unlikely to be good targets themselves in the search for habitable worlds, are potential hosts to large terrestrial satellites that would also exist in the habitable zone. In a new study led by Michelle Hill (University of Southern Queensland and University of New England, Australia; San Francisco State University), a team of scientists explores the occurrence rate of such moons.

    2
    Kepler has found more than 70 gas giants in their hosts’ habitable zones. These are shown in the plot above (green), binned according to the temperature distribution of their hosts and compared to the broader sample of Kepler planet candidates (grey). [Hill et al. 2018]

    A Giant-Planet Tally

    Hill and collaborators combine the known Kepler detections of giant planets located within their hosts’ optimistic habitable zones with calculated detection efficiencies that measure the likelihood that there are additional, similar planets that we’re missing. From this, the authors estimate the frequency with which we expect giant planets to occur in the habitable zones of different types of stars.

    The result: a frequency of 6.5 ± 1.9%, 11.5 ± 3.1%, and 6 ± 6% for giant planets lying in the habitable zones of G, K, and M stars, respectively. This is lower than the equivalent occurrence rate of habitable-zone terrestrial planets — which means that if the giant planets all host an average of one moon, habitable-zone rocky moons are less likely to exist than habitable-zone rocky planets. However, if each giant planet hosts more than one moon, the occurrence rates of moons in the habitable zone could quickly become larger than the rates of habitable-zone planets.

    3
    Distribution of the estimated planet–moon angular separation for known Kepler habitable-zone giant planets. Future missions would need to be able to resolve a separation between 1 and 90 microarcsec to detect potential moons. [Hill et al. 2018]

    Lessons from Our Solar System

    What can we learn from our own solar system? Of the ~185 moons known to orbit planets within our solar system, all but a few are in orbit around the gas giants. Jupiter, in particular, recently upped its tally to a whopping 79 moons! Gas giants therefore seem quite capable of hosting many moons.

    Could habitable-zone moons reasonably support life? Jupiter’s moon Io provides a good example of how radiative and tidal heating by the giant planet can warm a moon above the temperature of its surroundings. And Saturn’s satellite Ganymede demonstrates that large moons can even have their own magnetic fields, potentially shielding the moons’ atmospheres from their host planets.

    3
    NASA’s Galileo spacecraft acquired its highest resolution images of Jupiter’s moon Io on 3 July 1999 during its closest pass to Io since orbit insertion in late 1995. This color mosaic uses the near-infrared, green and violet filters (slightly more than the visible range) of the spacecraft’s camera and approximates what the human eye would see. Most of Io’s surface has pastel colors, punctuated by black, brown, green, orange, and red units near the active volcanic centers. A false color version of the mosaic has been created to enhance the contrast of the color variations.
    3 July 1999
    Source http://photojournal.jpl.nasa.gov/catalog/PIA02308
    Author NASA / JPL / University of Arizona

    4
    True color image of Ganymede, obtained by the Galileo spacecraft, with enhanced contrast.
    8 May 1998 (date of composite release); Galileo image taken on 26 June 1996.
    Source http://photojournal.jpl.nasa.gov/catalog/PIA00716
    Author NASA/JPL (edited by PlanetUser)

    Overall, it seems that the terrestrial satellites of habitable-zone gas giants are a valuable target to consider in the ongoing search for habitable worlds. Hill and collaborators’ work goes on to discuss observational strategies for detecting such objects, providing hope that future observations will bring us closer to detecting habitable moons beyond our solar system.

    Citation

    “Exploring Kepler Giant Planets in the Habitable Zone,” Michelle L. Hill et al 2018 ApJ 860 67. http://iopscience.iop.org/article/10.3847/1538-4357/aac384/meta

    Related journal articles
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    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
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  • richardmitnick 12:27 pm on December 27, 2017 Permalink | Reply
    Tags: , , , , , , Io, Scientists Discover Stromboli-Like Eruption on Volcanic Moon, ,   

    From Eos: “Scientists Discover Stromboli-Like Eruption on Volcanic Moon” 

    AGU bloc

    AGU
    Eos news bloc

    Eos

    12.27.17
    JoAnna Wendel

    1
    NASA’s New Horizons mission captured this composite image of an eruption on Jupiter’s moon Io while en route to Pluto in 2007. The erupting volcano is Tvashtar, in the northern hemisphere. New evidence suggests that Io can produce Stromboli-type eruptions, events never before observed on Io. The new data could help scientists figure out the makeup of Io’s interior. Credit: NASA/JPL/University of Arizona​

    NASA/New Horizons spacecraft

    Twenty years ago, “something huge, powerful, and energetic happened at the surface of Io,” said Ashley Davies, a volcanologist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Davies and his colleagues think they’ve discovered a type of eruption never before spotted on one of the most volcanically active bodies in the solar system.

    The researchers stumbled on the eruptive evidence in data from NASA’s Galileo orbiter mission, which explored the Jupiter system from 1995 to 2003. They think the data reflect a Strombolian eruption, a violent event named for Italy’s energetic Stromboli Volcano.

    1
    Stromboli, one of the world’s most active volcanoes, ejects large, hot volcanic bombs in this long-exposure image of the northeastern region of the summit crater terrace. During a May 2016 pilot project, the authors [Nicolas Turner, Bruce Houghton, Jacopo Taddeucci, Jost von der Lieth, Ullrich Kueppers, Damien Gaudin, Tullio Ricci, Karl Kim, and Piergiorgio Scalato 27 September 2017] sent unmanned aerial vehicles where humans couldn’t go to capture images and gather data on the locations and characteristics of Stromboli’s craters and vents. Credit: Rainer Albiez/Shutterstock.com

    But wait, you ask, didn’t Galileo plunge into Jupiter’s atmosphere at the end of its mission, way back in 2003?

    NASA/Galileo 1989-2003

    Well, yes. But the orbiter, at that point, had collected so much data about the Jovian system and its Galilean moons (Ganymede, Io, Callisto, and Europa) that scientists still haven’t waded through it all, even 14 years later.

    Davies presented the unpublished research on 13 December at the American Geophysical Union’s 2017 Fall Meeting in New Orleans, La.

    Serendipitous Data

    Io’s surface is constantly gushing lava—every million years or so, the entire moon’s surface completely regenerates. From towering lava fountains that can reach 400 kilometers high to violently bubbling lava lakes that burst through freshly cooled crust, these oozing lava fields can stretch many thousands of square kilometers.

    On this 3,600-kilometer-wide moon, eruptions take place “on a scale that simply isn’t seen on Earth today but was once common in Earth’s past,” Davies said. The scale, frequency, and intensity of Io’s eruptions make it a perfect analogue of early Earth, he continued, back when our blue planet was just a barren hellscape of lava.

    3
    A video of an Io eruption captured by New Horizons in 2007. Credit: NASA/Johns Hopkins University Applied Physics Laboratory

    Davies found evidence for the eruption he reported at Fall Meeting in data from Galileo’s Near Infrared Mapping Spectrometer (NIMS), which took pictures of the moon in the infrared wavelengths. This instrument allowed researchers to measure the thermal emissions, or heat, coming off the volcanically active moon.

    Stromboli Eruption

    While looking through the NIMS temperature data, Davies and his colleagues spotted a brief but intense moment of high temperatures that cooled oddly quickly. This signal showed up as a spike in heat from a region in the southern hemisphere called Marduk Fluctus. First, the researchers saw a heat signal jump to 4–10 times higher than background, or relatively normal, levels. Then just a minute later, the signal dropped about 20%. Another minute later, the signal dropped another 75%. Twenty-three minutes later, the signal had plummeted to the equivalent of the background levels.

    This signature resembled nothing Davies had seen before from Io. The lava flows and lava lakes are familiar: Their heat signals peter out slowly because as the surface of a lava flow cools, it creates a protective barrier of solid rock over a mushy, molten inside. Heat from magma underneath conducts through this newly formed crust and radiates from Io’s surface as it cools, which can take quite a long time.

    This new heat signature, on the other hand, represents a process never before seen on Io, Davies said: something intense, powerful, and—most important—fast.

    There’s only one likely explanation for what the instruments saw, explained Davies, whose volcanic expertise starts here on Earth. Large, violent eruptions like those seen at Stromboli are capable of spewing huge masses of tiny particles into the air, which cool quickly. See for yourself in this video of Stromboli erupting:

    As chance would have it, Galileo was likely in the right place at the right time to see the signatures of such an eruption on Io.

    Composition Questions

    Why do scientists care about an eruption on a moon nearly 630 million kilometers away?

    The temperature of Io’s lava dictates what kind of material makes up the moon, Davies said. For instance, if the rising magma erupts at temperatures of 1,800 or 1,900 K, it’s probably composed of komatiite, a rock extremely low in silicon. This rock is rarely found on Earth today, although scientists think it was commonly found during the Archaen eon 2.5–3.8 billion years ago, Earth’s early volcanic days. However, if the magma erupts at 1,400 or 1,500 K, that means it’s primarily made of basalt.

    The lava’s composition and temperature, in turn, can tell scientists what’s going on in the moon’s interior. Scientists aren’t yet sure how the push and pull from Jupiter’s gravity affect Io’s innards. Some have hypothesized that the grinding from the gravitational pull heats Io’s interior enough to produce a subsurface magma ocean.

    “Instead of being a completely fluid layer, Io’s magma ocean would probably be more like a sponge with at least 20% silicate melt within a matrix of slowly deformable rock,” said Christopher Hamilton, a planetary volcanologist at the University of Arizona’s Lunar and Planetary Science Laboratory in a prior press release about the push and pull of tidal forces on Io. Hamilton was not involved in this research.

    To help refine such hypotheses, scientists need the composition of melt and how hot it gets, Davies explained. But figuring out the precise heat of Io’s lava is tricky because regardless of its starting temperature, it cools relatively quickly. So even if the lava is made of komatiite, scientists may not be able to catch the signal before it cools to a temperature resembling that of basalt.

    The good news about large, Stromboli-type eruptions is that they expose vast areas of lava at incandescent temperatures. “So what we end up with is an event, if you can capture it, that will show a lot of lava at the temperature it erupted,” Davies said.

    Current and future probes can then home in on Marduk Fluctus for more detailed surveys to reveal such precise temperature data, Davies explained. However, until such future instruments launch, scientists still have mountains of Galileo data to get through.

    From Drone Peers into Open Volcanic Vents Further references with links:

    Bombrun, M., et al. (2015), Anatomy of a Strombolian eruption: Inferences from particle data recorded with thermal video, J. Geophys. Res. Solid Earth, 120, 2367–2387, https://doi.org/10.1002/2014JB011556.

    Burton, M., et al. (2007), Magmatic gas composition reveals the source depth of slug-driven Strombolian explosive activity, Science, 317, 227–230, https://doi.org/10.1126/science.1141900.

    Calvari, S., et al. (2016), Monitoring crater-wall collapse at active volcanoes: A study of the 12 January 2013 event at Stromboli, Bull. Volcanol., 78, 39, https://doi.org/10.1007/s00445-016-1033-4.

    Fornaciai, A., et al. (2010), A lidar survey of Stromboli volcano (Italy): Digital elevation model-based geomorphology and intensity analysis, Int. J. Remote Sens., 31, 3177–3194, https://doi.org/10.1080/01431160903154416.

    Gaudin, D., et al. (2014), Pyroclast tracking velocimetry illuminates bomb ejection and explosion dynamics at Stromboli (Italy) and Yasur (Vanuatu) volcanoes, J. Geophys. Res. Solid Earth, 119, 5384–5397, https://doi.org/10.1002/2014JB011096.

    Gaudin, D., et al. (2016), 3‐D high‐speed imaging of volcanic bomb trajectory in basaltic explosive eruptions, Geochem. Geophys. Geosyst., 17, 4268–4275, https://doi.org/10.1002/2016GC006560.

    Gurioli, L., et al. (2013), Classification, landing distribution, and associated flight parameters for a bomb field emplaced during a single major explosion at Stromboli, Italy, Geology, 41, 559–562, https://doi.org/10.1130/G33967.1.

    Harris, A. J. L., et al. (2013), Volcanic plume and bomb field masses from thermal infrared camera imagery, Earth Planet. Sci. Lett., 365, 77–85, https://doi.org/10.1016/j.epsl.2013.01.004.

    James, M. R., and S. Robson (2012), Straightforward reconstruction of 3D surfaces and topography with a camera: Accuracy and geoscience application, J. Geophys. Res., 117, F03017, https://doi.org/10.1029/2011JF002289.

    Patrick, M. R., et al. (2007), Strombolian explosive styles and source conditions: Insights from thermal (FLIR) video, Bull. Volcanol., 69, 769–784, https://doi.org/10.1007/s00445-006-0107-0.

    Rosi, M., et al. (2013), Stromboli volcano, Aeolian Islands (Italy): Present eruptive activity and hazards, Geol. Soc. London Mem., 37, 473–490, https://doi.org/10.1144/M37.14.

    Scarlato, P., et al. (2014), The 2014 Broadband Acquisition and Imaging Operation (BAcIO) at Stromboli Volcano (Italy), Abstract V41B-4813 presented at the 2014 Fall Meeting, AGU, San Francisco, Calif.

    Taddeucci, J., et al. (2007), Advances in the study of volcanic ash, Eos Trans. AGU, 88, 253, https://doi.org/10.1029/2007EO240001.

    Taddeucci, J., et al. (2012), High-speed imaging of Strombolian explosions: The ejection velocity of pyroclasts, Geophys. Res. Lett., 39, L02301, https://doi.org/10.1029/2011GL050404.

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  • richardmitnick 8:08 am on May 11, 2017 Permalink | Reply
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    From UC Berkeley: “Waves of lava seen in Io’s largest volcanic crater” 

    UC Berkeley

    UC Berkeley

    May 10, 2017
    Robert Sanders
    rlsanders@berkeley.edu

    1
    On March 8, 2015, Jupiter’s moon Europa passed in front of Io, allowing detailed mapping of the bright volcanic crater called Loki Patera (upper left). (Katherine de Kleer image.)

    Taking advantage of a rare orbital alignment between two of Jupiter’s moons, Io and Europa, researchers have obtained an exceptionally detailed map of the largest lava lake on Io, the most volcanically active body in the solar system.

    On March 8, 2015, Europa passed in front of Io, gradually blocking out light from the volcanic moon. Because Europa’s surface is coated in water ice, it reflects very little sunlight at infrared wavelengths, allowing researchers to accurately isolate the heat emanating from volcanoes on Io’s surface.

    The infrared data showed that the surface temperature of Io’s massive molten lake steadily increased from one end to the other, suggesting that the lava had overturned in two waves that each swept from west to east at about a kilometer (3,300 feet) per day.

    Overturning lava is a popular explanation for the periodic brightening and dimming of the hot spot, called Loki Patera after the Norse god. (A patera is a bowl-shaped volcanic crater.) The most active volcanic site on Io, which itself is the most volcanically active body in the solar system, Loki Patera is about 200 kilometers (127 miles) across. The hot region of the patera has a surface area of 21,500 square kilometers, larger than Lake Ontario.

    Earthbound astronomers first noticed Io’s changing brightness in the 1970s, but only when the Voyager 1 and 2 spacecraft flew by in 1979 did it become clear that this was because of volcanic eruptions on the surface. Despite highly detailed images from NASA’s Galileo mission in the late 1990s and early 2000s, astronomers continue to debate whether the brightenings at Loki Patera – which occur every 400 to 600 days – are due to overturning lava in a massive lava lake, or periodic eruptions that spread lava flows over a large area.
    “If Loki Patera is a sea of lava, it encompasses an area more than a million times that of a typical lava lake on Earth,” said Katherine de Kleer, a UC Berkeley graduate student and the study’s lead author. “In this scenario, portions of cool crust sink, exposing the incandescent magma underneath and causing a brightening in the infrared.”


    A simulation of two resurfacing waves sweeping around Loki Patera at different rates and converging in the southeast corner. (Katherine de Kleer video)

    “This is the first useful map of the entire patera,” said co-author Ashley Davies, of the Jet Propulsion Laboratory in Pasadena, who has studied Io’s volcanoes for many years. “It shows not one but two resurfacing waves sweeping around the patera. This is much more complex than what was previously thought”.

    “This is a step forward in trying to understand volcanism on Io, which we have been observing for more than 15 years, and in particular the volcanic activity at Loki Patera,” said Imke de Pater, a UC Berkeley professor of astronomy.

    De Kleer is lead author of a paper reporting the new findings that will be published May 11 in the journal Nature.

    Binocular telescope turns two eyes on Io

    The images were obtained by the twin 8.4-meter (27.6-foot) mirrors of the Large Binocular Telescope Observatory in the mountains of southeast Arizona, linked together as an interferometer using advanced adaptive optics to remove atmospheric blurring.

    U Arizona Large Binocular Telescope, Mount Graham, Arizona, USA

    The facility is operated by an international consortium headquartered at the University of Arizona in Tucson.


    Animation of Europa sweeping across Loki Patera and obscuring different portions of its floor. The lower panels show the infrared intensity of the lava lake as a function of time as it is covered (ingress) and uncovered (egress) by Europa. The red curve is the best-fit map to the observations. (Katherine de Kleer video)

    “Two years earlier, the LBTO had provided the first ground-based images of two separate hot spots within Loki Patera, thanks to the unique resolution offered by the interferometric use of LBT, which is equivalent to what a 23-meter (75-foot) telescope would provide,” noted co-author and LBTO director Christian Veillet. “This time, however, the exquisite resolution was achieved thanks to the observation of Loki Patera at the time of an occultation by Europa.”

    Europa took about 10 seconds to completely cover Loki Patera. “There was so much infrared light available that we could slice the observations into one-eighth-second intervals during which the edge of Europa advanced only a few kilometers across Io’s surface,” said co-author Michael Skrutskie, of the University of Virginia, who led the development of the infrared camera used for this study. “Loki was covered from one direction but revealed from another, just the arrangement needed to make a real map of the distribution of warm surface within the patera.”

    These observations gave the astronomers a two-dimensional thermal map of Loki Patera with a resolution better than 10 kilometers (6.25 miles), 10 times better than normally possible with the LBT Interferometer at this wavelength (4.5 microns). The temperature map revealed a smooth temperature variation across the surface of the lake, from about 270 Kelvin at the western end, where the overturning appeared to have started, to 330 Kelvin at the southeastern end, where the overturned lava was freshest and hottest.
    Using information on the temperature and cooling rate of magma derived from studies of volcanoes on Earth, de Kleer was able to calculate how recently new magma had been exposed at the surface. The results – between 180 and 230 days before the observations at the western end and 75 days before at the eastern – agree with earlier data on the speed and timing of the overturn.

    Interestingly, the overturning started at different times on two sides of a cool island in the center of the lake that has been there ever since Voyager photographed it in 1979.

    2
    A heat map of Io’s lava lake Loki Patera, showing how the surface is cooler in the northwest (1 and 2) where the lava overturn began, and hottest in the southeast (3), where the hotter magma was more recently exposed. The entire lake surface overturned in about three months time. Katherine de Kleer graphic.

    “The velocity of overturn is also different on the two sides of the island, which may have something to do with the composition of the magma or the amount of dissolved gas in bubbles in the magma,” de Kleer said. “There must be differences in the magma supply to the two halves of the patera, and whatever is triggering the start of overturn manages to trigger both halves at nearly the same time but not exactly. These results give us a glimpse into the complex plumbing system under Loki Patera.”

    Lava lakes like Loki Patera overturn because the cooling surface crust slowly thickens until it becomes denser than the underlying magma and sinks, pulling nearby crust with it in a wave that propagates across the surface. According to de Pater, as the crust breaks apart, magma may spurt up as fire fountains, akin to what has been seen in lava lakes on Earth, but on a smaller scale.

    4
    From their infrared measurements, the team deduced the age of the lava at the surface of Loki Patera. The youngest is in the lower right, having overturned most recently, about 75 days before the observations. Katherine de Kleer graphic.De Kleer and de Pater are eager to observe other Io occultations to verify their findings, but they’ll have to wait until the next alignment in 2021. For now, de Kleer is happy that the interferometer linking the two telescopes, the adaptive optics on each and the unique occultation came together as planned that night two years ago.

    “We weren’t sure that such a complex observation was even going to work,” she said, “but we were all surprised and pleased that it did.”

    In addition to de Kleer, Skrutskie, Davies, Veillet and de Pater, co-authors of the paper are J. Leisenring, P. Hinz, E. Spalding and A. Vaz of the University of Arizona’s Steward Observatory, and Al Conrad of the Large Binocular Telescope Observatory, A. Resnick of Amherst College, V. Bailey of Stanford University, D. Defrère of the University of Liège, A. Skemer of UC Santa Cruz and C.E. Woodward of the University of Minnesota.

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  • richardmitnick 4:15 pm on September 11, 2015 Permalink | Reply
    Tags: , , Io, ,   

    From Goddard: “Underground Magma Ocean Could Explain Io’s ‘Misplaced’ Volcanoes” 

    NASA Goddard Banner
    Goddard Space Flight Center

    Sep. 10, 2015
    William Steigerwald
    NASA’s Goddard Space Flight Center

    1
    This five-frame sequence of images from the New Horizons spacecraft captures the giant plume from Io’s Tvashtar volcano. Credits: NASA/JHU Applied Physics Laboratory/Southwest Research Institute

    “This is the first time the amount and distribution of heat produced by fluid tides in a subterranean magma ocean on Io has been studied in detail,” said Robert Tyler of the University of Maryland, College Park and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We found that the pattern of tidal heating predicted by our fluid-tide model is able to produce the surface heat patterns that are actually observed on Io.” Tyler is lead author of a paper on this research published June 2015 in the Astrophysical Journal Supplement Series.

    Io is the most volcanically active world in the solar system, with hundreds of erupting volcanoes blasting fountains of lava up to 250 miles (about 400 kilometers) high. The intense geological activity is the result of heat produced by a gravitational tug-of-war between Jupiter’s massive gravity and other smaller but precisely timed pulls from Europa, a neighboring moon to Io that orbits further from Jupiter. Io orbits faster, completing two orbits every time Europa finishes one. This regular timing means that Io feels the strongest gravitational pull from its neighbor in the same orbital location, which distorts Io’s orbit into an oval shape. This modified orbit causes Io to flex as it moves around Jupiter, causing material within Io to shift position and generate heat by friction, just as rubbing your hands together briskly makes them warmer.

    2
    This is a composite image of Io and Europa taken March 2, 2007 with the New Horizons spacecraft. Here Io is at the top with three volcanic plumes visible. The 300-kilometer (190-mile) high plume from the Tvashtar volcano is at the 11 o’clock position on Io’s disk, with a smaller plume from the volcano Prometheus at the 9 o’clock position on the edge of Io’s disk, and the volcano Amirani between them along the line dividing day and night. Credits: NASA/JHU Applied Physics Laboratory/Southwest Research Institute

    Previous theories of how this heat is generated within Io treated the moon as a solid but deformable object, somewhat like clay. However, when scientists compared computer models using this assumption to a map of the actual volcano locations on Io, they discovered that most of the volcanoes were offset 30 to 60 degrees to the East of where the models predicted the most intense heat should be produced.

    The pattern was too consistent to write it off as a simple anomaly, such as magma flowing diagonally through cracks and erupting nearby. “It’s hard to explain the regular pattern we see in so many volcanoes, all shifting in the same direction, using just our classical solid-body tidal heating models,” said Wade Henning of the University of Maryland and NASA Goddard, a co-author of the paper.

    The mystery of Io’s misplaced volcanoes called for a different explanation—one that had to do with the interaction between heat produced by fluid flow and heat from solid-body tides.

    “Fluids – particularly ‘sticky’ (or viscous) fluids – can generate heat through frictional dissipation of energy as they move,” said co-author Christopher Hamilton of the University of Arizona, Tucson. The team thinks much of the ocean layer is likely a partially molten slurry or matrix with a mix of molten and solid rock. As the molten rock flows under the influence of gravity, it may swirl and rub against the surrounding solid rock, generating heat. “This process can be extremely effective for certain combinations of layer thickness and viscosity which can generate resonances that enhance heat production,” said Hamilton.

    The team thinks a combination of fluid and solid tidal heating effects may best explain all the volcanic activity observed on Io. “The fluid tidal heating component of a hybrid model best explains the equatorial preference of volcanic activity and the eastward shift in volcano concentrations, while simultaneous solid-body tidal heating in the deep-mantle could explain the existence of volcanoes at high latitudes,” said Henning. “Both solid and fluid tidal activity generate conditions that favor each other’s existence, such that previous studies might have been only half the story for Io.”

    The new work also has implications for the search for extraterrestrial life. Certain tidally stressed moons in the outer solar system, such as Europa and Saturn’s moon Enceladus, harbor oceans of liquid water beneath their icy crusts. Scientists think life might originate in such oceans if they have other key ingredients thought to be necessary, such as chemically available energy sources and raw materials, and they have existed long enough for life to form. The new work suggests that such subsurface oceans, whether composed of water or of any other liquid, will be more common and last longer than expected, both within our solar system and beyond.

    Just as a precisely timed push on a swing will make it go higher, oceans can fall into a resonance state and sometimes produce significant heat through tidal flow. “Long-term changes in heating or cooling rates within a subsurface ocean are likely to produce a combination of ocean layer thickness and viscosity that generates a resonance and produces considerable heat,” said Hamilton. “Therefore the mystery may be not how such subsurface oceans could survive, but how they could perish. Consequently, subsurface oceans within Io and other satellites could be even more common than what we’ve been able to observe so far.”

    The research was funded by a grant from the NASA Outer Planets Research program.

    For earlier related Io volcano research, visit:

    http://www.nasa.gov/topics/solarsystem/features/io-volcanoes-displaced.html

    See the full article here .

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