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  • richardmitnick 12:22 pm on July 11, 2021 Permalink | Reply
    Tags: "Continental pirouettes", , , , , , , , Subduction,   

    From GFZ German Research Centre Helmholtz Centre for Geosciences Potsdam: “Continental pirouettes” 

    From GFZ German Research Centre Helmholtz Centre for Geosciences Potsdam


    The plates of the Earth’s crust perform complicated movements that can be attributed to quite simple mechanisms. That is the short version of the explanation of a rift that began to tear the world apart over a length of several thousand kilometers 105 million years ago. The scientific explanation appears today in the journal Nature Geoscience.

    According to the paper, a super volcano split the Earth’s crust over a length of 7,500 kilometers, pushing the Indian Plate away from the African Plate. The cause was a “plume” in the Earth’s mantle, i.e. a surge of hot material that wells upwards like an atomic mushroom cloud in super slow motion. It has long been known that the Indian landmass thus made its way northward and bumped into Eurasia. But a seemingly counterintuitive east-west movement of the continental plates was also part of the process. This is supported by calculations by a team led by Dutch scientist Douwe van Hinsbergen (Utrecht University [ Universiteit Utrecht] (NL)) and Bernhard Steinberger (GFZ German Research Centre for Geosciences).

    According to the findings, the Indian Plate did not simply move away from Africa, but rotated in the process. The reason for this is the subcontinent, whose land mass acts on the much larger continental plate like an axis around which the entire plate rotates. In the south, the scissors opened, in the north they closed – there, mountain-building processes and the subduction of crustal plates were induced.

    This has dramatic effects up to the present time: The subduction processes continue and trigger earthquakes again and again in the Mediterranean region between Cyprus and Turkey. The traces of the plume and the supervolcano can still be identified today. They are flood basalts on Madagascar and in the southwest of India. They testify to immense volcanic activity fed by the mantle plume.

    Bernhard Steinberger has calculated the movement and pressure that the super volcano near present-day Madagascar could cause further north on the Arabian Peninsula and in what is now the Mediterranean. He has also published a “kitchen table experiment on Youtube” which illustrates the movements.

    See the full article here.


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    Helmholtz-Zentrum Potsdam – Deutsches GeoForschungsZentrum GFZ

    The Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences

    Our vision

    The future can only be secured by those who understand the System Earth and its interactions with Man: We develop a profound understanding of systems and processes of the solid Earth together with strategies and options for action to address global change and its regional impacts, to understand natural hazards and to minimize associated risks, as well as to assess the human impact on System Earth.
    Earth System Science for the Future

    The GFZ is Germany’s national research center for the solid Earth Sciences. Our mission is to deepen the knowledge of the dynamics of the solid Earth, and to develop solutions for grand challenges facing society. These challenges include anticipating the hazards arising from the Earth’s dynamic systems and mitigating the associated risks to society; securing our habitat under the pressure of global change; and supplying energy and mineral resources for a rapidly growing population in a sustainable manner and without harming the environment.

    These challenges are inextricably linked with the dynamics of planet Earth, not just the solid Earth and the surface on which we live, but also the hydrosphere, atmosphere, and biosphere, and the chemical, physical, and biological processes that connect them. Hence, we view our planet as a system with interacting components. We investigate the structure and history of the Earth, its properties, and the dynamics of its interior and surface, and we use our fundamental understanding to develop solutions needed to maintain planet Earth as a safe and supportive habitat.

    Our expertise

    In pursuit of our mission, we have developed a comprehensive spectrum of expertise in geodesy, geophysics, geology, mineralogy, geochemistry, physics, geomorphology, geobiosciences, mathematics, and engineering. This is complemented by our deep methodological and technological knowhow and innovation. We are responsible for the long-term operation of expansive instrument networks, arrays and observatories, as well as data and analytical infrastructures. To accomplish our large-scale tasks, we have established MESI, the worldwide unique Modular Earth Science Infrastructure.

    Our research is organized in a matrix structure, with disciplinary competences grouped in four scientific departments. The departments guarantee the development and continuity of disciplinary skills, methods, and infrastructures. This is an indispensable foundation for our ability to engage with evolving scientific insights, new technologies, and unexpected, pressing challenges of societal relevance.

    The grand challenges and the complexity of system Earth on the other hand, require a close multidisciplinary interaction and integration across scientific competence fields to secure advances in understanding and solutions. For these reasons, and to achieve our scientific mission, we coordinate our research via five Research Units (RU) that foster the required long-term research collaborations and that transcend the organizational / management units. These five RUs are:

    Global Processes – Integrated monitoring and modelling: How are linked processes controlling the global dynamics of the Earth and change in the Earth System?

    Plate Boundary Systems – Understanding the dynamics that affect the human habitat: How do the dynamic processes of the solid Earth’s most dynamic systems function and how do they control related hazards and resource formation?

    Earth Surface and Climate Interactions – Probing records to constrain mechanisms and sensitivities: How does climate change today and in the past affect the Earth surface and how do surface processes, in turn, influence the atmosphere and climate?

    Natural Hazards – Understanding risks and safeguarding the human habitat: How can we better predict and understand natural hazards, their dynamics, and their consequences?

    Georesources and Geoenergy – Raw materials and contributions to the energy transition: How can georesources and the geological subsurface be used in a sustainable way?

  • richardmitnick 10:25 am on May 27, 2021 Permalink | Reply
    Tags: "UArizona Geologists to 'X-ray' the Andes", , , , , , , One of the most extensive network of earthquake sensors-seismometers-to ever be installed in the Andes region of South America., Orogeny-mountain building, Subduction, TANGO-Trans Andean Great Orogeny, The formation of mountain ranges.,   

    From University of Arizona (US) : “UArizona Geologists to ‘X-ray’ the Andes” 

    From University of Arizona (US)


    Media contact
    Daniel Stolte
    Science Writer, University Communications

    Researcher contact
    Susan Beck
    Department of Geosciences

    A network of seismic stations poised to record images from deep underground will help scientists understand the mechanisms driving the formation of mountain ranges in unprecedented detail.

    Andean Mountain range in Argentina showing the snow-capped peak of Aconcagua, the tallest mountain in the Americas, rising 22,837 feet above sea level. Credit: Peter DeCelles.

    Led by geoscientists at the University of Arizona, an international research team will use data from earthquakes, geology and geochemistry to study, in greater detail than ever before, how mountain ranges are built.

    Supported by a $3 million grant from the National Science Foundation (US), the project will shed light on how the Andes in South America formed, and produce a 3D model of mountain-building based on the Andes as a natural laboratory.

    The project, which is part of the NSF Frontier Research in Earth Science program, is dubbed TANGO, which stands for Trans Andean Great Orogeny. At the heart of the project is one of the most extensive network of earthquake sensors-seismometers-to ever be installed in the Andes region of South America. Scientists will use seismic waves traveling through Earth’s interior from quakes around the globe to better understand the geologic processes underlying the formation of mountain ranges.

    TANGO will focus specifically on the Andes from northern to southern Chile and in Argentina.

    “TANGO is an excellent example of the type of international collaboration that characterizes the University of Arizona’s unique capacity to tackle the grand challenges of our time,” said University of Arizona President Robert C. Robbins. “Building on our strengths and ongoing research in the geosciences, our faculty laid the groundwork that allowed them to successfully assemble an international team to help us gain a better understanding of a natural process where there is still a lot to learn.”

    Susan Beck, a UArizona professor of geosciences, will serve as TANGO’s lead principal investigator, with co-principal investigators Barbara Carrapa, Peter DeCelles, Mihai Ducea and Eric Kiser of the UArizona Department of Geosciences.

    A major part of the TANGO project centers around seismic imaging, which works much like medical imaging such as CT scans, which use X-ray images to make tissues visible based on their densities. Just like bone and soft tissue show up as different features, geologic features beneath the Earth’s surface show up distinctly when geologists “X-ray” them by recording shockwaves from earthquakes as they travel through the Andes.

    “Instead of sending X-rays through your head, we use seismic waves,” Beck said. “We deploy our instruments across a large area, and we wait for earthquakes to happen. We might take a year’s worth of data, from which we then assemble a tomographic image of what’s down there.”

    While many of the processes involved in mountain-building — known as orogeny — are known to take place at the surface, other processes take place very deep inside the Earth, hidden from view. Seismic imaging allows researchers to probe the Earth’s interior down to about 700 miles, Beck said.

    “Combined with geologic and geochemistry data from the rocks, we can understand how the Andes formed over the last 90 million years,” she said.

    Along the western edge of South America, a chunk of ocean floor known as the Nazca plate pushes against its neighbor — the plate that contains the South American continent — at a rate of a little over 2 inches per year. This process, known as subduction, causes Earth’s crust to fold up, pushing up mountain peaks up to 20,000 feet in elevation.

    “Subduction affects almost every aspect of our lives,” Beck said. “Think of it as a recycling program for Earth’s crust; it affects where mountains will rise up, where minerals and ores are formed, where tension is released as earthquakes and where the largest volcanic eruptions occur.”

    Piecing Together ‘A Giant Puzzle’

    Geologists still only have a vague idea of the details of mountain-building processes, Beck said, and TANGO is poised to fill some of the gaps.

    “For example, we know that as one plate goes under the other, it causes earthquakes, it drags layers of rock down with it and causes volcanoes to erupt,” she said. “But what happens with that molten rock before it gets to the surface? How deep does the Nazca plate go before it gets assimilated into the mantle?”

    The Andes serve as a giant natural laboratory to study the complex process involved in building a mountain range, Beck said.

    “When you make mountains, rocks erode, and all that eroded rock has to go somewhere,” Beck said. “In a large mountain range like the Andes, that eroded material adds up.”

    As debris from the eroding mountains accumulates in basins on the east side of the Andes, it creates a layered archive of time that “is amazing to unravel,” Beck said, but also presents geologists with head-scratchers.

    The east face of Aconcagua clearly shows the layers of the lavas and volcanic deposits that make up the mountain. The large glacier on the northeast face is known as the Polish Glacier. Credit: Peter DeCelles.

    “We have a decent understanding of the big picture, but we don’t really understand the dynamics of it in detail,” Beck said. “For example, we find deposits from those basins high up in the mountains, and we don’t really know how they ended up there, so it’s like a giant puzzle.”

    Beck said she is excited about the seismic imaging component of TANGO.

    “Each seismic wave has a travel time that we can measure,” she said. “The time it takes a seismic wave to get from the epicenter of an earthquake to our station depends on the materials it travels through at different speeds, and we can unravel that. For example, a seismic wave that goes through a magma body really slows down compared to a wave that doesn’t, and we will see that difference.”

    To record thousands of earthquakes occurring in South America and around the globe, the team will install seismic stations across an area measuring about 800 miles by 400 miles. Deploying the technology in the field will involve many students from UArizona and partner institutions.

    “Some stations are easy, as they are in readily accessible locations and we just need to dig a hole and insert the sensors,” Beck said, “but others are in very remote locations, at high elevations. Some seismic stations require building a vault, mounting solar panels and batteries so the seismic station can run for years.”

    TANGO differs from similar efforts in scope and scale, Beck said.

    “In a typical scenario, people would put these stations out for a month, pull them up and call it good, but we will be going into very remote areas, and we will have to deploy our instruments over many months to years. We look at this as our one-time chance to get the data that could help us answer these fundamental questions. It’s going to be a huge field effort.”

    Since orogenic mechanisms are not unique to the Andes, TANGO will help scientists better understand tectonic processes in other areas as well. Beck said the Andes are a modern analog for what the western margin of North America looked like between 70 and 90 million years ago.

    “Similar processes have happened through geologic time in many places throughout the world,” she said.

    See the full article here .

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    As of 2019, the University of Arizona (US) enrolled 45,918 students in 19 separate colleges/schools, including the UArizona College of Medicine in Tucson and Phoenix and the James E. Rogers College of Law, and is affiliated with two academic medical centers (Banner – University Medical Center Tucson and Banner – University Medical Center Phoenix). UArizona is one of three universities governed by the Arizona Board of Regents. The university is part of the Association of American Universities and is the only member from Arizona, and also part of the Universities Research Association(US). The university is classified among “R1: Doctoral Universities – Very High Research Activity”.

    Known as the Arizona Wildcats (often shortened to “Cats”), the UArizona’s intercollegiate athletic teams are members of the Pac-12 Conference of the NCAA. UArizona athletes have won national titles in several sports, most notably men’s basketball, baseball, and softball. The official colors of the university and its athletic teams are cardinal red and navy blue.

    After the passage of the Morrill Land-Grant Act of 1862, the push for a university in Arizona grew. The Arizona Territory’s “Thieving Thirteenth” Legislature approved the UArizona in 1885 and selected the city of Tucson to receive the appropriation to build the university. Tucson hoped to receive the appropriation for the territory’s mental hospital, which carried a $100,000 allocation instead of the $25,000 allotted to the territory’s only university (Arizona State University(US) was also chartered in 1885, but it was created as Arizona’s normal school, and not a university). Flooding on the Salt River delayed Tucson’s legislators, and by they time they reached Prescott, back-room deals allocating the most desirable territorial institutions had been made. Tucson was largely disappointed with receiving what was viewed as an inferior prize.

    With no parties willing to provide land for the new institution, the citizens of Tucson prepared to return the money to the Territorial Legislature until two gamblers and a saloon keeper decided to donate the land to build the school. Construction of Old Main, the first building on campus, began on October 27, 1887, and classes met for the first time in 1891 with 32 students in Old Main, which is still in use today. Because there were no high schools in Arizona Territory, the university maintained separate preparatory classes for the first 23 years of operation.


    UArizona is classified among “R1: Doctoral Universities – Very high research activity”. UArizona is the fourth most awarded public university by National Aeronautics and Space Administration(US) for research. UArizona was awarded over $325 million for its Lunar and Planetary Laboratory (LPL) to lead NASA’s 2007–08 mission to Mars to explore the Martian Arctic, and $800 million for its OSIRIS-REx mission, the first in U.S. history to sample an asteroid.

    The LPL’s work in the Cassini spacecraft orbit around Saturn is larger than any other university globally. The UArizona laboratory designed and operated the atmospheric radiation investigations and imaging on the probe. UArizona operates the HiRISE camera, a part of the Mars Reconnaissance Orbiter. While using the HiRISE camera in 2011, UArizona alumnus Lujendra Ojha and his team discovered proof of liquid water on the surface of Mars—a discovery confirmed by NASA in 2015. UArizona receives more NASA grants annually than the next nine top NASA/JPL-Caltech(US)-funded universities combined. As of March 2016, the UArizona’s Lunar and Planetary Laboratory is actively involved in ten spacecraft missions: Cassini VIMS; Grail; the HiRISE camera orbiting Mars; the Juno mission orbiting Jupiter; Lunar Reconnaissance Orbiter (LRO); Maven, which will explore Mars’ upper atmosphere and interactions with the sun; Solar Probe Plus, a historic mission into the Sun’s atmosphere for the first time; Rosetta’s VIRTIS; WISE; and OSIRIS-REx, the first U.S. sample-return mission to a near-earth asteroid, which launched on September 8, 2016.

    UArizona students have been selected as Truman, Rhodes, Goldwater, and Fulbright Scholars. According to The Chronicle of Higher Education, UArizona is among the top 25 producers of Fulbright awards in the U.S.

    UArizona is a member of the Association of Universities for Research in Astronomy(US), a consortium of institutions pursuing research in astronomy. The association operates observatories and telescopes, notably Kitt Peak National Observatory(US) just outside Tucson. Led by Roger Angel, researchers in the Steward Observatory Mirror Lab at UArizona are working in concert to build the world’s most advanced telescope. Known as the Giant Magellan Telescope(CL), it will produce images 10 times sharper than those from the Earth-orbiting Hubble Telescope.

    Giant Magellan Telescope, 21 meters, to be at the NOIRLab(US) National Optical Astronomy Observatory(US) Carnegie Institution for Science’s(US) Las Campanas Observatory(CL), some 115 km (71 mi) north-northeast of La Serena, Chile, over 2,500 m (8,200 ft) high.

    The telescope is set to be completed in 2021. GMT will ultimately cost $1 billion. Researchers from at least nine institutions are working to secure the funding for the project. The telescope will include seven 18-ton mirrors capable of providing clear images of volcanoes and riverbeds on Mars and mountains on the moon at a rate 40 times faster than the world’s current large telescopes. The mirrors of the Giant Magellan Telescope will be built at UArizona and transported to a permanent mountaintop site in the Chilean Andes where the telescope will be constructed.

    Reaching Mars in March 2006, the Mars Reconnaissance Orbiter contained the HiRISE camera, with Principal Investigator Alfred McEwen as the lead on the project. This National Aeronautics and Space Administration(US) mission to Mars carrying the UArizona-designed camera is capturing the highest-resolution images of the planet ever seen. The journey of the orbiter was 300 million miles. In August 2007, the UArizona, under the charge of Scientist Peter Smith, led the Phoenix Mars Mission, the first mission completely controlled by a university. Reaching the planet’s surface in May 2008, the mission’s purpose was to improve knowledge of the Martian Arctic. The Arizona Radio Observatory(US), a part of UArizona Department of Astronomy Steward Observatory(US), operates the Submillimeter Telescope on Mount Graham.

    The National Science Foundation(US) funded the iPlant Collaborative in 2008 with a $50 million grant. In 2013, iPlant Collaborative received a $50 million renewal grant. Rebranded in late 2015 as “CyVerse”, the collaborative cloud-based data management platform is moving beyond life sciences to provide cloud-computing access across all scientific disciplines.
    In June 2011, the university announced it would assume full ownership of the Biosphere 2 scientific research facility in Oracle, Arizona, north of Tucson, effective July 1. Biosphere 2 was constructed by private developers (funded mainly by Texas businessman and philanthropist Ed Bass) with its first closed system experiment commencing in 1991. The university had been the official management partner of the facility for research purposes since 2007.

    U Arizona mirror lab-Where else in the world can you find an astronomical observatory mirror lab under a football stadium?

    University of Arizona’s Biosphere 2, located in the Sonoran desert. An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

  • richardmitnick 4:03 pm on January 19, 2021 Permalink | Reply
    Tags: "Going with the grains to explain a fundamental tectonic force", , Subduction, Tiny mineral grains — squeezed and mixed over millions of years — set in motion the chain of events that plunge massive tectonic plates deep into the Earth’s interior.,   

    From Yale University: “Going with the grains to explain a fundamental tectonic force” 

    From Yale University

    January 18, 2021
    Science contact
    Fred Mamoun

    Jim Shelton

    Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Credit: Wikipedia.

    A new study suggests that tiny, mineral grains — squeezed and mixed over millions of years — set in motion the chain of events that plunge massive tectonic plates deep into the Earth’s interior.

    The theory, proposed by Yale scientists David Bercovici and Elvira Mulyukova, may provide an origin story for subduction, one of the most fundamental forces responsible for the dynamic nature of the planet.

    The study appears in the PNAS.

    Subduction occurs when one tectonic plate slides underneath another plate and then sinks into the Earth’s mantle. Its role in major geological processes is immense: It is the main engine for tectonic motion. It builds mountains, triggers earthquakes, forms volcanoes, and drives the geologic carbon cycle.

    The tectonic plates of the world were mapped in 1996, USGS.

    Yet researchers have been uncertain about what initiates subduction.

    “Why Earth even has subduction, unlike other terrestrial planets as far as we know, is a mystery,” said Bercovici, Yale’s Frederick William Beinecke Professor and chair of Earth and Planetary Sciences.

    “Mantle rock near the surface that has cooled for hundreds of millions of years has two competing effects,” he said. “While it’s gotten colder and heavier and wants to sink, it’s also gotten stiffer and doesn’t want to sink. The stiffening effect should win out, as it does on most planets, but on Earth, for some reason, it doesn’t.”

    A conceptual sketch of the ocean basin setting for the new model. Inset images from a computer model show mineral fraction, grain size, and weakness. Credit: Elvira Mulyukova and David Bercovici.

    According to the theoretical model developed by Bercovici and Mulyukova, a research scientist at Yale, subduction may initiate at the margins between Earth’s sea floor and continents.

    The model shows that tectonic stresses in an oceanic plate cause its mineral grains to mix with each other, become damaged, and eventually shrink. Over a period of approximately 100 million years, this process weakens the oceanic plate and makes it susceptible to vertical shear and bending — which are associated with the start of subduction.

    “The real bottleneck for tectonic plate activity on a terrestrial planet is how fast its massive, rocky layers can deform,” said Mulyukova. “The rocks can deform only as fast as their tiny mineral grains allow. Our model explains how these changes in mineral grains can dramatically weaken the rock and make subduction possible on a planet like Earth.”

    This research was supported by a grant from the National Science Foundation.

    See the full article here .


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    Yale University comprises three major academic components: Yale College (the undergraduate program), the Graduate School of Arts and Sciences, and the professional schools. In addition, Yale encompasses a wide array of centers and programs, libraries, museums, and administrative support offices. Approximately 11,250 students attend Yale.

  • richardmitnick 8:08 am on October 21, 2017 Permalink | Reply
    Tags: Atlas of The Underworld, , , , Subduction   

    From Science Alert: “Scientists Are Mapping an Atlas of The Underworld Hidden Far Beneath Our Feet” 


    Science Alert

    21 OCT 2017

    Utrecht University

    For as long as humans have been around we’ve been fascinated by the world hiding underneath the surface of the Earth, and now scientists are systematically mapping the positions of the tectonic plates that have been pushed deeper into the planet’s core.

    It’s called the Atlas of the Underworld and you can view it online – measurements go down up to 2,900 kilometres (1,800 miles) in some cases. The focus is on ‘dead’ tectonic plates, pushed down to the bottom of the Earth’s mantle and no longer part of the surface.

    The Atlas has been produced through 15 years of work by the team from Utrecht University in the Netherlands, pulling together data from multiple sources as well as from their own seismic scans, using sound waves to measure the geological make-up of the ground.

    “This is the first time that the slabs all over the world have been mapped,” says one of the researchers, Wim Spakman. “Much of the information was already available, but mostly in the form of more or less isolated research projects. We have put all the pieces together, rather like a jigsaw.”

    Credit: Atlas of the Underworld

    As tectonic plates of crust and mantle shift on the surface of the Earth, they’re causing volcanic activity and earthquakes, and sometimes triggering a process called subduction, where one plate is forced down into the Earth as it moves.

    The part of the plates being subducted are then termed “slabs”, as Spakman mentions above. These slabs can exist for millions of years without being melted by the heart of the Earth’s core, and the new Atlas tracks 94 of them across the globe.

    “Now we can trace not only how plates move over the surface, but how they sink to the core-mantle boundary,” one of the team, Douwe van Hinsbergen, told Ryan F. Mandelbaum at Gizmodo. “That’s the cool thing for me – we can learn about the physics inside the Earth.”

    The researchers have been able to tie slabs to their period of subduction, as well as to associated volcanic activity on the surface, or to mountain ranges still visible today, like the Andes or the Himalayas.

    Not only is it an impressive catalogue of the subterranean world, the Atlas can also teach scientists about how the mantle works – the pressures and timescales and movements involved in this hidden underworld.

    We can learn more about how the planet is evolving and how all of us living on the surface could be affected in the future: the Atlas has already been used to calculate CO2 emitted by volcanic activity, for instance, and how sea levels have changed over millions of years.

    Through the Atlas, the scientists have also discovered a Slab Deceleration Zone some 1,500-2,000 kilometres (932-1,243 miles) below the surface, where slabs slow down but don’t stop, before later accelerating towards the core.

    And the team is hoping many more discoveries like this will happen in the future as the underworld map gets refined and expanded.

    “Making an atlas is a long-term work of precision, and the end result may at first sight look like a coffee table book,” says van Hinsbergen.

    “But it should be remembered how often people use world atlases for purposes that never crossed the maker’s mind. We expect the same to be true of the Atlas of the Underworld for geoscientists.”

    The research has been published in Tectonophysics.

    See the full article here .

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  • richardmitnick 6:46 pm on September 8, 2014 Permalink | Reply
    Tags: , , , , , , , Subduction   

    From SPACE.com: “Jupiter’s Moon Europa May Have Plate Tectonics Just Like Earth” 

    space-dot-com logo


    September 08, 2014
    Mike Wall

    Jupiter’s icy moon Europa, regarded as perhaps the solar system’s best bet to host alien life, keeps getting more and more interesting.

    Scientists have found evidence of an active plate tectonics system within the ice shell of Jupiter’s moon Europa. Earth has long been thought to be the only solar system body with plate tectonics.
    Credit: NASA/JPL/Ted Stry

    Big slabs of ice are sliding over and under each other within Europa’s ice shell, a new study suggests. The Jovian satellite may thus be the only solar system body besides Earth to possess a system of plate tectonics.

    “From a purely science or geological perspective, this is incredible,” study lead author Simon Kattenhorn of the University of Idaho told Space.com. “Earth may not be alone. There may be another body out there that has plate tectonics. And not only that, it’s ice!” [Photos: Europa, Mysterious Icy Moon of Jupiter]

    Artist’s concept of the subduction process thought to be occurring on Jupiter’s moon Europa, showing how a cold outer portion of Europa’s ice shell moved into the warmer shell interior and was ultimately absorbed. A “subsumption band” was created at the surface in the overriding plate, alongside which cryolavas may have erupted.
    Credit: Noah Kroese, I.NK

    The new results come less than a year after plumes of water vapor were spotted erupting from Europa’s south polar region. That find excited astrobiologists a great deal, because it suggested that a robotic probe may be able to sample the moon’s subsurface ocean of liquid water at a distance, without even touching down.

    “There have been a lot of recent exciting discoveries [about Europa],” Kattenhorn said. “All taken together, as NASA starts thinking about future missions, I’m hoping it will be pretty clear: This [Europa] is the obvious choice.”

    Missing puzzle pieces

    Kattenhorn and co-author Louise Prokter, of Johns Hopkins University’s Applied Physics Laboratory, studied photos of Europa taken by NASA’s Galileo spacecraft, which orbited Jupiter from 1995 until 2003.


    The researchers used the images to reconstruct the recent geological history of a 52,000-square-mile (134,000 square kilometers) swath of Europa — an area about the size of the state of Alabama. They noticed that the region changed over time, with some surface features becoming mismatched relative to the architecture captured in earlier images.

    False-color image of Europa’s trailing northern hemisphere, where subduction zones indicative of a system of plate tectonics are thought to exist.
    Credit: NASA/JPL/University of Arizona

    “It was very clear that you could reconstruct the original picture simply by moving plates around,” Kattenhorn said, comparing the duo’s approach to assembling a jigsaw puzzle.

    Further, there was a gap in this reconstructed picture, as if a large puzzle piece had fallen off the table. In a sense, that’s probably what did happen, Kattenhorn said.

    “In this case, the big chunk had actually moved down underneath the adjacent plate and was forever lost, recycled into the interior” of Europa’s ice shell, he said.

    That chunk was indeed big, about the size of the state of Massachusetts, Kattenhorn added.

    Plate tectonics

    Kattenhorn and Prokter think this phenomenon of one plate sliding under another, which is known as subduction, is the most likely explanation for the disappearing puzzle piece. They cite several lines of supporting evidence, including potential “cryolavas” of water ice near the plate boundary. (On Earth, volcanism is common along subduction zones.)

    If the scientists’ interpretation — laid out in a study published online today (Sept. 7) in the journal Nature Geoscience— is correct, planetary science textbooks will have to be rewritten.

    “Plate tectonics has been thought to be unique to our world,” Michelle Selvans, of the Smithsonian National Air and Space Museum, wrote in an accompanying News and Views piece in the same issue of Nature Geoscience.

    “Subduction zones, convergent boundaries where one tectonic plate slides under another and is recycled into the Earth’s mantle, are unique to plate tectonic systems,” Selvans wrote. “Although Mercury, Venus and Marsshow clear signs of tectonic activity, such as systems of thrust faults and rift valleys, none of these rocky planets have been convincingly shown to have a system of moving tectonic plates, either today or in the past.”

    An active system of plate tectonics could also explain two puzzling facts about Europa, Kattenhorn said: 1) why its surface is so young (less than 90 million years, as estimated by meteorite-impact rates), and 2) how the moon accommodates the creation of new ice on its shell, which has been observed previously. (Europa isn’t getting any bigger, so some process must be balancing out the production of new material.)

    “From my perspective, that’s pretty exciting, that we’ve addressed these two really important questions about Europa,” Kattenhorn said.

    He and Prokter said Europa likely has a system of cold, brittle plates moving around above convecting warmer ice. The mechanisms behind Europan plate tectonics are unclear at the moment, Kattenhorn said, stressing the need for modeling work. But tidal heating generated by the tug of Jupiter’s immense gravity, the same phenomenon that keeps Europa’s interior ocean from freezing up, may be one of the ultimate drivers, he added.

    Close-up view of a possible zone of plate spreading on Europa, showing internal striations related to spreading and bilateral symmetry about a central axis. Older geological features can be matched perfectly to either side of the spreading zone. (This image focuses on a different region of Europa than the one analyzed for the Nature Geoscience paper published on Sept. 7, 2014.)
    Credit: NASA/JPL

    Implications for life?

    Scientists are eager to learn if Europa’s huge subsurface ocean harbors alien life. See how Jupiter’s icy moon Europa works in this SPACE.com infographic.
    Credit: by Karl Tate, Infographics Artist

    Some scientists think plate tectonics were essential to the rise of life on Earth. For example, the idea goes, the movement of plates replenishes nutrients and helps stabilize the planet’s climate by recycling carbon.

    So it’s natural to wonder if Europan plate tectonics may make the icy moon more habitable for simple lifeforms, Selvans wrote.

    “Perhaps Europa and Earth are even more uniquely similar: It is tempting to note the correlation between the existence of both life and plate tectonics on Earth and wonder if the latter might not be a requirement of the former,” she wrote.

    Europa’s ice shell is thought to be 12 to 19 miles (20 to 30 kilometers) thick, and subducting plates likely dive down only a mile so, Kattenhorn said. Subduction, therefore, probably doesn’t take any nutrients or other complex molecules from the surface down into the ocean immediately.

    But this could happen indirectly and over longer periods of time via convection, he added.

    “As with all convection, what goes up must go down as well,” Kattenhorn said. “One can imagine that some of that material may ultimately, just by virtue of being in a convective system, work its way downward. Whether that ultimately comes into contact with the ocean is an important question.”

    And there may be pockets of liquid water within the ice shell relatively close to the surface, perhaps close enough to be reached by a subducting Europan plate, he added.

    “People who are thinking about habitable environments — certainly not my field of expertise — that would probably be something very interesting for them to think about,” Kattenhorn said.

    See the full article here.

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