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  • richardmitnick 10:10 am on April 28, 2019 Permalink | Reply
    Tags: , , , , , , Glaciology, Jupiter's Europa moon, , , OPAG-Outer Planet Assessment Group   

    From Nautilus: “Why Europa Is the Place to Go for Alien Life” 

    Nautilus

    From Nautilus

    April 18, 2019
    Corey S. Powell

    1
    This image shows a view of the trailing hemisphere of Jupiter’s ice-covered satellite, Europa, in approximate natural color. Long, dark lines are fractures in the crust, some of which are more than 3,000 kilometers (1,850 miles) long. The bright feature containing a central dark spot in the lower third of the image is a young impact crater some 50 kilometers (31 miles) in diameter. This crater has been provisionally named “Pwyll” for the Celtic god of the underworld. Europa is about 3,160 kilometers (1,950 miles) in diameter, or about the size of Earth’s moon. This image was taken on September 7, 1996, at a range of 677,000 kilometers (417,900 miles) by the solid state imaging television camera onboard the Galileo spacecraft during its second orbit around Jupiter. The image was processed by Deutsche Forschungsanstalt fuer Luftund Raumfahrt e.V., Berlin, Germany. NASA/JPL/DLR.

    NASA/Galileo 1989-2003

    I have seen the future of space exploration, and it looks like a cue ball covered with brown scribbles. I am talking about Europa, the 1,940-mile-wide, nearly white, and exceedingly smooth satellite of Jupiter. It is an enigmatic world that is, in many ways, almost a perfect inversion of Earth. It is also one of the most plausible places to look for alien life. If it strikes you that those two statements sound rather contradictory—why yes, they do. And therein lies the reason why Europa just might be the most important world in the solar system right now. The Europa Clipper spacecraft is scheduled to launch in 2023 to probe the mysterious moon, according to NASA’s 2020 budget proposal.

    NASA/Europa Clipper annotated

    The unearthly aspects of Europa are literally un-earthly : This is an orb sculpted from water ice, not from rock. It has ice tectonics in place of shifting continents, salty ocean in place of mantle, and vapor plumes in place of volcanoes. The surface scribbles may be dirty ocean material that leaked up through the icy equivalent of an earthquake fault.

    From a terrestrial perspective, Europa is built all wrong, with its solid crust up top and water down below. From the perspective of alien life, though, that might be a perfectly dandy arrangement. Beneath its frozen crust, Europa holds twice as much liquid water as exists in all of our planet’s oceans combined. Astrobiologists typically flag water as life’s number-one requirement; well, Europa is drowning in it. Just below the ice line, conditions might resemble the environment on the underside of Antarctic ice sheets. At the bottom of its buried ocean, Europa may have an active system of hydrothermal vents. Both of these are vibrant habitats on Earth.

    Adding a new twist to the story, Europa’s water may sometimes escape its icy confines. On at least four occasions, the Hubble Space Telescope has detected what appear to be large plumes of water vapor erupting from Europa. That detection has confirmed and expanded on the scientific ideas about what makes Europa such a dynamic world. Europa travels in a slightly oval orbit around Jupiter, causing it to get alternately squeezed and stretched by the giant planet’s gravity. The flexing creates intense friction inside the satellite and generates enough heat to maintain a warm ocean beneath Europa’s frozen outer shell. The presence of a plume suggests that the stretching of Europa also opens and closes a network of fissures that allow buried water to erupt as geysers.

    If the geysers consist of ocean water shooting all the way through the crust, they could carry traces of aquatic life with them. And if the plumes rise high enough, a future spacecraft could fly right through them, sniffing for biochemicals.

    2
    SIGNS FROM BELOW: Salty seawater appears to have breached Europa’s frozen exterior, creating a network of red-brown streaks. Perhaps traces of aquatic life were carried along in the process? This scene is 100 miles wide. NASA/JPL-Caltech/SETI Institute

    You can see why people were giddy at a 2015 OPAG meeting held at NASA’s Ames Research Center. A regular forum for geeking out about ice worlds, the OPAG gatherings—short for Outer Planet Assessment Group—feel halfway between the corporate swarm of a MacWorld expo and a vinyl record fair. They are where true believers mingle with the newbies, showing off the latest science, kicking around speculative ideas, and developing strategies for exploration. With each new bit of data, they have grown increasingly convinced that Europa, not Mars, is the place to go to search for alien life. Finding the plume on Europa was another shot of adrenaline. The room went fervently silent as Lorenz Roth of Sweden’s Royal Institute of Technology, calling in via a fuzzy phone line, reported on the latest search for a recurrence of such water eruptions (no luck yet, alas).

    Another significant piece of news was hanging over the OPAG meeting: The discovery that Europa has plate tectonics, like Earth and unlike any other world we know of. Tectonics describes a process in which the crust moves about and cycles back and forth into the interior. Louise Prockter of Johns Hopkins University’s Applied Physics Laboratory co-discovered this style of activity on Europa by painstakingly reconstructing old images from the Galileo spacecraft, which circled Jupiter from 1995 to 2003. (Analysis of other Galileo data suggests the probe flew right past a Europan water plume in 1997, but scientists didn’t realize it at the time.)

    As Prockter explained to me at the meeting, a mobile crust potentially does two important things. It cycles surface ice, along with all the compounds it develops during exposure to the sun, down into the dark ocean; that chemical flow could be crucial for supplying the ocean with nutrients. The motion of the crust also brings ocean material up to the surface, where prying human eyes can seek clues about the Europan ocean without actually drilling down into it.

    Bolstered by these discoveries, the cult of Europa has now escaped the confines of the OPAG meetings. A successful mission to Europa would bring into focus the incredible ice-and-ocean environment of Europa. It would also help scientists understand ice worlds in general. Icy moons, dwarf planets, and giant asteroids are the norm in the vast outer zone of the solar system, and if they repeat the pattern of Europa they may contain much of the solar system’s habitable real estate. There is good reason to think that ice worlds are similarly abundant around other stars as well. Putting all of these new ideas together suggests that the Milky Way may collectively contain tens of billions of life-friendly iceboxes.

    But if these stunning extrapolations seem to suggest that scientists are starting to get a handle on how Europa works, allow me to suggest otherwise. Europa is still largely a big, icy ball of confusion.

    3
    Under the Ice: An artist’s conception of Europa (foreground), Jupiter (right) and Jupiter’s innermost large moon, Io (middle), shows salts bubbling up from Europa’s liquid ocean to reach its frozen surface. NASA/JPL-Caltech.

    Almost everything we know about the surface of Europa comes from NASA’s Galileo mission, which reached Jupiter in 1995. During its eight-year mission, Galileo mapped most of Europa, but at a crude resolution of about one mile per pixel. For comparison, today’s best Mars images show features as small as three feet. Elizabeth “Zibi” Turtle of the Hopkins Applied Physics Lab promises that the camera on NASA’s upcoming Europa probe will achieve a similar level of clarity. Until then, imagine trying to navigate using a map that doesn’t show anything smaller than one mile and you will get a sense of how far the Europa scientists have to go.

    What’s more, at a very basic level, planetary scientists still do not have a good handle on how geology (or maybe we should say “glaciology?”) works in frozen settings. Ice, you see, is not just ice. Robert Pappalardo of NASA’s Jet Propulsion Laboratory, the ponytail-wielding mission scientist for the agency’s upcoming Europa probe, spelled out some of the complexities to me. On Europa, surface temperatures on a warm day at the equator might rise up to -210 degrees Fahrenheit; at the poles, the lows plunge to -370 degrees Fahrenheit. Under those conditions, water is properly thought of as a mineral, and ice has approximately the consistency of concrete. In many ways it is remarkably similar to rock in how it fractures, faults, and shatters. But even in such a deep freeze, surface ice can sublimate—evaporate directly from solid to gas—in a way that rock does not. Icy material tends to boil off from darker, warmer regions and collect on lighter, cooler ones, producing an exotic kind of weathering that rearranges the landscape without any wind or rain.

    All sorts of other things are happening on the surface of Europa. Jupiter has a huge, potent magnetic field that bombards its satellite with radiation: about 500 rem per day on average, which you can more easily judge as a dose strong enough to make you sick in one hour and to kill you in 24. That radiation quickly breaks down any organic compounds, greatly complicating the search for life, but produces all kinds of other complex chemistry. A lab experiment at the Jet Propulsion Laboratory suggests that the colors of Europa’s streaks are produced by irradiated ocean salts. These and other fragmented molecules, along with a steady rain of organic material delivered by comet impacts, could be used as energy sources for life when they circulate back down into the ocean, where any living things would be well protected.

    The movement of Europa’s crust—its icy outer shell—is another broad area of mystery. On ice worlds, Pappalardo notes, water takes on the role of magma and hot rock deep below the surface, but once again ice and rock are not quite the same. Warm ice turns soft, almost slushy, under high pressure and slowly flows. There could be complicated circulation patterns contained entirely within the crust, which is perhaps 10 to 15 miles thick (or maybe more or less; that is yet another mystery that the Europa mission will investigate). Pools of liquid water might exist trapped within the shell, cut off from the underlying ocean. Plumes of water at the surface might not originate directly from the ocean; it is possible that they come from these intermediate lakes, analogous to the largely unexplored Lake Vostok in Antarctica.

    At the OPAG meeting, seemingly narrow arguments about the circulation of ice sparked colorful debates about prospects for life on Europa and, by extension, on the myriad other ice worlds out there. Britney Schmidt of Georgia Tech wondered if the active geology (glaciology) on Europa occurs entirely within the crust. If material does not circulate at all between surface and ocean, Europa is sealed tight. Life could not get any fresh chemicals from up above, and if it somehow manages to survive anyway we might never know unless we find a way to dig a hole all the way through. Several researchers at OPAG suggested that meaningful answers will require a surface lander; one energetic audience member repeatedly argued for sending an impactor—a high-speed bowling ball, essentially—to smack the surface and shake loose any possible buried microbes.

    As for the Europan ocean itself, that runs even deeper into what you might call aqua incognita . If the surface truly is streaked with salts, as the recent experiments indicate, that suggests a mineral-rich ocean in which waters interact vigorously with a rocky seafloor at the bottom. A likely source of such interaction is a network of hydrothermal vents powered by Europa’s internal heat; such vents could provide chemical energy to sustain Europan life, as they do on Earth. But how much total hydrothermal activity goes on? Are the acidity and salinity conducive to life? How much organic material is down there? The scientists egged each other on with provocative questions that, as yet, have no answers.

    When (or if) we will find out will depend, in large part, on how much of Europa’s inner nature is evident from the outside. The conversations at OPAG sometimes devolved into something resembling a college existential argument: If an alien swims in Europa’s ocean and nobody is able to see it, is it really alive?

    The Europa faithful have been waiting a long time for a mission that would wipe away those kinds of arguments, or at least ground them in hard data. That wait has been full of whipsaw swings between optimism and disappointment. NASA’s planned Europa Orbiter got a green light in 1999, only to be cancelled in 2002. The agency rebounded with a proposal for an even more ambitious, nuclear-propelled Jupiter Icy Moons Orbiter, which looked incredible until it got delayed and finally cancelled in 2006. A proposed joint venture with the European Space Agency never even got that far, though the Europeans are going ahead with their part of the project, which will send a probe to Ganymede, another one of Jupiter’s icy moons, in 2030.

    The Europa Clipper, outfitted with scientific instruments that include cameras and spectrometers, will swoop repeatedly past the moon and produce images that determine its composition. There is a chance the Europa mission will include a lander. Funding does not exist yet, but Adam Steltzner—the hearty engineer who figured out how to land the two-ton Curiosity rover safely on Mars—assures me that from a technical standpoint it would not be difficult to design a small probe equipped with rockets to allow a soft touchdown on Europa. There it could drill into the surface and search for possible organic material that has not been degraded by the radiation blasts from Jupiter.

    What you won’t see, the OPAG boffins all sadly agreed, is one of those cool Europa submarines that show up on the speculative “future mission concept” NASA web pages. Getting a probe into Lake Vostok right here on Earth has proven a daunting challenge. Drilling through 10 miles or more of Europan ice and exploring an alien ocean by remote control is something we still don’t know how to do, and certainly not with any plausible future NASA budget.

    No matter. Even the no-frills version of NASA’s current Europa plan will unleash a flood of information about how ice worlds work, and about how likely they are to support life. If the answers are as exciting as many scientists hope—and as I strongly expect—it will bolster the case for future missions to Titan, Enceladus, and some of Europa’s other beckoning cousins. It will reshape the search for habitable worlds around other stars as well. Right now astronomers are mostly focused on finding other Earthlike planets, but maybe that is not where most of the action is. Perhaps most of the life in the universe is locked away, safe but almost undetectable, beneath shells of ice.

    Whether or not Europa is home to alien organisms, it will tell us about the range of what life can be, and where it can be. That one icy moon will help cure science of its rocky-planet chauvinism. Hey, who you calling cue ball?

    See the full article here .

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  • richardmitnick 8:12 pm on September 11, 2018 Permalink | Reply
    Tags: , Glaciology, ICESat-2-Ice andCloud and Land Elevation Satellite, Succeeds the original ICESat-1 satellite that operated from 2003 to 2009, Two areas of intense interest for long-term tracking: massive glaciers covering Antarctica and Greenland and sea surface height in the Arctic and other oceans, , UW’s Applied Physics Laboratory   

    From University of Washington: “UW polar scientists advised NASA on upcoming ICESat-2 satellite” 

    U Washington

    From University of Washington

    September 10, 2018
    Hannah Hickey

    NASA ICESat 2

    NASA plans to launch a new satellite this month that will measure elevation changes on Earth with unprecedented detail. Once in the air, it will track shifts in the height of polar ice, mountain glaciers and even forest cover around the planet.

    Two University of Washington polar scientists are advising the ICESat-2 mission scheduled to launch Sept. 15 from California’s Vandenberg Air Force Base. UW researchers provided expertise in two areas of intense interest for long-term tracking: massive glaciers covering Antarctica and Greenland, and sea surface height in the Arctic and other oceans.

    “ICESat-2 is designed to answer a simple glaciology question very, very well: It will tell us where, and how fast, the ice sheets are thickening and thinning,” said Benjamin Smith, a glaciologist at the UW’s Applied Physics Laboratory. “When these data start coming in we will immediately get a big-picture map of how Antarctica and Greenland have changed over the past decade.”

    Smith is a member of the science definition team and the lead author of the document that describes the data that ICESat-2 will provide for ice that covers land.

    “My specific role is to work out how to turn the raw data that NASA generates — which track the location of individual photons — into the answer we want to give the scientific community, which is how high the ice sheet surface is at a particular point,” Smith said.

    The instrument, whose full name is the Ice, Cloud, and Land Elevation Satellite, succeeds the original ICESat-1 satellite that operated from 2003 to 2009. Since then NASA has been running annual IceBridge flights to collect data over a few important parts of Antarctica and Greenland during the gap. The new satellite will provide nonstop, higher-resolution data for the Earth sciences community starting this October, one month after it launches.

    “For me, the most exciting aspect of ICESat-2 is its extremely fine resolution,” said Jamie Morison, a polar oceanographer and former leader of the North Pole Environmental Observatory. The new satellite uses six laser beams to get readings every 2-3 feet, each one focused over a 30-foot patch of the surface. For comparison, Morison said, today’s instruments measure surface elevation by averaging over many hundreds of feet to miles between each data point. The new instrument’s orbit is designed to collect more data over the poles, and it can detect very small elevation changes over long timescales.

    Morison is a physical oceanographer on the science definition team, and lead author the document that describes ICESat-2 data for the open oceans.

    “For the oceans, ICESat-2 will yield fine-scale measurements that are important to coastal oceanography, revealing smaller features in the open ocean and even down to the characteristics of larger surface waves,” Morison said. “ICESat-2 will also help measure sea-level change, particularly at high latitudes where the most established radar altimeters don’t go, and it will give us higher-resolution measurements of the sea surface slopes that drive changing ocean circulation.”

    The two UW researchers were members of a 12-person science team that consulted on the project over the years leading up to the launch. They also are among the hundreds of scientists who anticipate using the data in their research.

    “ICESat-2 observations will make it possible to study glaciers that are too remote for aircraft to reach, and it will make it possible to detect small changes over large areas, which were difficult to see clearly with older data,” Smith said. “There are a lot of places in Antarctica where we assume that not much is happening, but we don’t have great evidence one way or another. My guess is that when we look carefully, there will be a lot to see.”

    For more information, contact Smith at besmith@uw.edu or 206-616-9176 and Morison at jhm2@uw.edu or 206-543-1394. More ICESat-2 multimedia is here.

    See the full article here .


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  • richardmitnick 11:40 am on February 15, 2017 Permalink | Reply
    Tags: An entire landscape possibly reshaping itself, An iceberg nearly seven times the size of New York City, Antarctic Peninsula’s Larsen C ice shelf, , Glaciology, How ice shelves break, Iceberg calving on a grand scale, UK-based Project MIDAS monitoring the rift via satellites   

    From GIZMODO: “What Happens When That Enormous Antarctic Ice Shelf Finally Breaks?” 

    GIZMODO bloc

    GIZMODO

    2.15.17
    Maddie Stone

    1
    Rift in the Larsen C ice shelf photographed by NASA’s IceBridge aerial survey in November 2016. Image: NASA/John Sonntag

    For the past few months, scientists have watched with bated breath as a rift in the Antarctic Peninsula’s Larsen C ice shelf grows longer by the day. Eventually, the rift will make a clean break, expelling a 2,000 square mile chunk of ice into the sea. It’ll be an epic sight to behold—but what happens after the ice is gone?

    Glaciologists, who have been tracking the rift since it first appeared on the Larsen C ice shelf in 2014, are now scrambling to answer that very question. So-called iceberg calving is a natural geophysical process along the Antarctica’s frosty fringes; think of it as the planetary equivalent of your fingernails growing too long and breaking off. But this is one of the largest such events on record, with the potential to dramatically reshape the entire peninsula.

    Moreover, while there’s little direct evidence linking the Larsen C ice shelf breakup to climate change, scientists worry that the processes playing out here could be but a taste of what’s to come for West Antarctica, as rising air and sea temperatures cause this vast, icy mantle to weaken from above and below.

    “What we’re worried about is what we’re seeing here is going to happen everywhere else,” Thomas Wagner, director of NASA’s polar science program told Gizmodo. “[Larsen C] is a natural laboratory for understanding how ice shelves break.”

    2
    Timelapse of the growing rift in the Larsen C ice shelf captured by ESA’s Sentinel-1 satellite. Image: Project MIDAS

    Over 100 miles long, up to two miles wide, and lengthening at a rate of five football fields per day, the rift in the Larsen C ice shelf has been in and out of the spotlight since it first emerged on the eastern flank of the Antarctic Peninsula in 2014. Since punching its way through a section of softer, more ductile ice, the rift has followed a predictable pattern—periods of quietude, punctuated by sudden growth spurts—that experts say is typical of ice shelf calving. But over the last two months, things have accelerated “quite a lot,” according to Martin O’Leary, a glaciologist with the UK-based Project MIDAS, which is monitoring the rift via satellites. “Now we’re paying attention to every satellite image that comes through to see if it jumps again,” he told Gizmodo.

    Having grown an impressive 17 miles (27 km) since December, the Larsen C rift has about 12 miles (20 km) to go before it reaches the other end of the shelf, snaps off, and spits out an iceberg nearly seven times the size of New York City.

    This could happen any day. “It could go tomorrow, it could go in a year’s time,” O’Leary said, adding that the ice “has to leave eventually.” That’s because additional ice is constantly pushing seaward from the peninsula’s interior, exerting a powerful shear force on the ever-weakening shelf.

    The good news is, we don’t have to worry about Larsen C’s breakup contributing to sea level rise. Ice shelves are, by definition, already sitting on top of water. “It’s already made its sea level rise contribution,” O’Leary said.

    3
    The ice shelves at the tip of the Antarctic Peninsula have been changing dramatically in recent decades, as illustrated in this composite satellite photo showing the historic ice extent prior to calving events. Image: NASA Earth Observatory

    Aside from possibly setting a few penguins adrift, the real concern with Larsen C’s imminent calving is what it’ll mean for the rest of the shelf—and for the ice currently tethered to land on the Antarctic Peninsula, which can still contribute to sea level rise, albeit probably just a few millimeters. Glaciologists often liken ice shelves to corks in a champagne bottle: remove them, and all the stuff they’ve bottled up starts to escape. This may be especially true for the Larsen C ice shelf, which appears to be snapping off at two crucial pinning points where land meets ice.

    “We expect this to create a new zone where calving happens more readily, now that we’ve removed these pinning points,” Wagner said. “And when these ice shelves break up, the ice behind surges into the ocean, getting thinner.”

    In other words, Larsen C’s soon-to-be iceberg could be the tip of a much larger, proverbial iceberg, of an entire landscape reshaping itself. The changes glaciologists expect around Larsen C jibe with a bigger-picture pattern of ice retreat across the peninsula, including earlier calving events at the neighboring ice shelves Larsen A and B, which scientists have attributed to rising temperatures.

    Whether or not climate change is playing a direct role in the action on Larsen C, it’s a clearly force to be reckoned with across the Antarctic Peninsula, where average temperatures have risen a staggering 3 degrees Celsius (5.4 degrees Fahrenheit) since pre-industrial times. (Globally-averaged temperatures have risen roughly a single degree Celsius over the same time period.)

    “We may see that one this chunk of [ice] is gone, Larsen C [starts] becoming more vulnerable to climate impacts,” O’Leary said.

    4
    Bird’s eye view of the Amundsen sea embayment, where major glaciers of the West Antarctic ice sheet empty into the ocean. Pope, Smith, and Kohler glaciers were the focus of this study. Image: NASA/GSFC/SVS

    Most importantly to researchers, the breakup of the Larsen C ice shelf could be a harbinger of what’s to come in other vulnerable parts of West Antarctica, particularly the Amundsen Sea embayment to the south, where warming waters are already causing the enormous Pine Island and Thwaites glaciers to melt and retreat. A summary of a scientific workshop compiled last year by the National Snow and Ice Data Center warns that “a significant retreat of the Thwaites Glacier system would trigger a wider collapse of most of the West Antarctic Ice Sheet.” That entire ice sheet contains enough water to raise global sea level by 3.3 meters (over ten feet), on a timescale of decades to centuries.

    “This is going to happen on other ice shelves,” Wagner said, adding that NASA and others have a unique opportunity with Larsen C, to study a massive iceberg calving event from satellites, airborne surveys like Operation IceBridge, and ground-based data. “We’re gonna watch how the ice shelf responds mechanically [as it breaks]. Larsen C is how we model what’s going to happen to Thwaites.”

    In other words, far more disturbing than the breakup of the Larsen C ice shelf is what it can tell us about our future.

    See the full article here .

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