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71 views · Jun 21st
A new analysis of Venus' surface shows evidence of tectonic motion in the form of crustal blocks that have jostled against each other like broken chunks of pack ice. The movement of these blocks could indicate that Venus is still geologically active and give scientists insight into both exoplanet tectonics and the earliest tectonic activity on Earth. "We've identified a previously unrecognized pattern of tectonic deformation on Venus, one that is driven by interior motion just like on Earth," says Paul Byrne, associate professor of planetary science at North Carolina State University and lead and co-corresponding author of the work. "Although different from the tectonics we currently see on Earth, it is still evidence of interior motion being expressed at the planet's surface." The finding is important because Venus has long been assumed to have an immobile solid outer shell, or lithosphere, just like Mars or Earth's moon. In contrast, Earth's lithosphere is broken into tectonic plates, which slide against, apart from, and underneath each other on top of a hot, weaker mantle layer. Byrne and an international group of researchers used radar images from NASA's Magellan mission to map the surface of Venus. In examining the extensive Venusian lowlands that make up most of the planet surface, they saw areas where large blocks of the lithosphere seem to have moved: pulling apart, pushing together, rotating and sliding past each other like broken pack ice over a frozen lake. The team created a computer model of this deformation, and found that sluggish motion of the planet's interior can account for the style of tectonics seen at the surface. "These observations tell us that interior motion is driving surface deformation on Venus, in a similar way to what happens on Earth," Byrne says. "Plate tectonics on Earth are driven by convection in the mantle. The mantle is hot or cold in different places, it moves, and some of that motion transfers to Earth's surface in the form of plate movement. "A variation on that theme seems to be playing out on Venus as well. It's not plate tectonics like on Earth—there aren't huge mountain ranges being created here, or giant subduction systems—but it is evidence of deformation due to interior mantle flow, which hasn't been demonstrated on a global scale before." The deformation associated with these crustal blocks could also indicate that Venus is still geologically active. "We know that much of Venus has been volcanically resurfaced over time, so some parts of the planet might be really young, geologically speaking," Byrne says. "But several of the jostling blocks have formed in and deformed these young lava plains, which means that the lithosphere fragmented after those plains were laid down. This gives us reason to think that some of these blocks may have moved geologically very recently—perhaps even up to today." The researchers are optimistic that Venus' newly recognized "pack ice" pattern could offer clues to understanding tectonic deformation on planets outside of our solar system, as well as on a much younger Earth. "The thickness of a planet's lithosphere depends mainly upon how hot it is, both in the interior and on the surface," Byrne says. "Heat flow from the young Earth's interior was up to three times greater than it is now, so its lithosphere may have been similar to what we see on Venus today: not thick enough to form plates that subduct, but thick enough to have fragmented into blocks that pushed, pulled, and jostled." NASA and the European Space Agency recently approved three new spacecraft missions to Venus that will acquire observations of the planet's surface at much higher resolution than Magellan. "It's great to see renewed interest in the exploration of Venus, and I'm particularly excited that these missions will be able to test our key finding that the planet's lowlands have fragmented into jostling crustal blocks," Byrne says. The work appears in Proceedings of the National Academy of Sciences. Sean Solomon of Columbia University is co-corresponding author. Richard Ghail of the University of London, Surrey; A. M. Celâl Sengör of Istanbul Technical University; Peter James of Baylor University; and Christian Klimczak of the University of Georgia also contributed to the work. https://phys.org/news/2021-06-ice-tectonics-reveal-venus-geological.html
61 views · Jun 21st
The most severe mass extinction event in the past 540 million years eliminated more than 90 percent of Earth's marine species and 75 percent of terrestrial species. Although scientists had previously hypothesized that the end-Permian mass extinction, which took place 251 million years ago, was triggered by voluminous volcanic eruptions in a region of what is now Siberia, they were not able to explain the mechanism by which the eruptions resulted in the extinction of so many different species, both in the oceans and on land. Associate professor Laura Wasylenki of Northern Arizona University's School of Earth and Sustainability and Department of Chemistry and Biochemistry is co-author on a new paper in Nature Communications entitled, "Nickel isotopes link Siberian Traps aerosol particles to the end-Permian mass extinction," in collaboration with Chinese, Canadian and Swiss scientists. The paper presents the results of nickel isotope analyses performed in Wasylenki's lab on Late Permian sedimentary rocks collected in Arctic Canada. The samples have the lightest nickel isotope ratios ever measured in sedimentary rocks, and the only plausible explanation is that the nickel was sourced from the volcanic terrain, very likely carried by aerosol particles and deposited in the ocean, where it dramatically changed the chemistry of seawater and severely disrupted the marine ecosystem. "The study results provide strong evidence that nickel-rich particles were aerosolized and dispersed widely, both through the atmosphere and into the ocean," Wasylenki said. "Nickel is an essential trace metal for many organisms, but an increase in nickel abundance would have driven an unusual surge in productivity of methanogens, microorganisms that produce methane gas. Increased methane would have been tremendously harmful to all oxygen-dependent life." NAU associate professor Laura Wasylenki is co-author on a new paper in Nature Communications entitled, "Nickel isotopes link Siberian Traps aerosol particles to the end-Permian mass extinction," in collaboration with Chinese, Canadian and Swiss scientists. Credit: Northern Arizona University "Our data provide a direct link between global dispersion of Ni-rich aerosols, ocean chemistry changes and the mass extinction event," Wasylenki said. "The data also demonstrate that environmental degradation likely began well before the extinction event—perhaps starting as early as 300,000 years before then. Prior to this study, the connection between Siberian Traps flood basalt volcanism, marine anoxia and mass extinction was rather vague, but now we have evidence of a specific kill mechanism. This finding demonstrates the power of nickel isotope analyses, which are relatively new, to solve long-standing problems in the geosciences." Wasylenki, who joined NAU in 2018, was formerly an igneous petrologist and then a specialist in calcite crystal growth and biomineralization. She now focuses on the use of metal stable isotope geochemistry to address geological, environmental and biological questions. Many of her recent and current projects have investigated metal isotope effects at solid-fluid interfaces, in particular during metal adsorption to oxyhydroxide mineral particles. This work has implications for ancient and modern geochemical cycles and environmental metal transport. Wasylenki's lab group, named Systematic Experimental Study and Analysis of Metals in the Environment (SESAME Lab), focuses on two main research themes, the cycling of transition metals in modern and ancient oceans and the environmental transport of toxic heavy metals. https://phys.org/news/2021-06-geochemical-end-permian-mass-extinction-event.html
79 views · Jun 21st

More from 777 times

71 views · Jun 21st
A new analysis of Venus' surface shows evidence of tectonic motion in the form of crustal blocks that have jostled against each other like broken chunks of pack ice. The movement of these blocks could indicate that Venus is still geologically active and give scientists insight into both exoplanet tectonics and the earliest tectonic activity on Earth. "We've identified a previously unrecognized pattern of tectonic deformation on Venus, one that is driven by interior motion just like on Earth," says Paul Byrne, associate professor of planetary science at North Carolina State University and lead and co-corresponding author of the work. "Although different from the tectonics we currently see on Earth, it is still evidence of interior motion being expressed at the planet's surface." The finding is important because Venus has long been assumed to have an immobile solid outer shell, or lithosphere, just like Mars or Earth's moon. In contrast, Earth's lithosphere is broken into tectonic plates, which slide against, apart from, and underneath each other on top of a hot, weaker mantle layer. Byrne and an international group of researchers used radar images from NASA's Magellan mission to map the surface of Venus. In examining the extensive Venusian lowlands that make up most of the planet surface, they saw areas where large blocks of the lithosphere seem to have moved: pulling apart, pushing together, rotating and sliding past each other like broken pack ice over a frozen lake. The team created a computer model of this deformation, and found that sluggish motion of the planet's interior can account for the style of tectonics seen at the surface. "These observations tell us that interior motion is driving surface deformation on Venus, in a similar way to what happens on Earth," Byrne says. "Plate tectonics on Earth are driven by convection in the mantle. The mantle is hot or cold in different places, it moves, and some of that motion transfers to Earth's surface in the form of plate movement. "A variation on that theme seems to be playing out on Venus as well. It's not plate tectonics like on Earth—there aren't huge mountain ranges being created here, or giant subduction systems—but it is evidence of deformation due to interior mantle flow, which hasn't been demonstrated on a global scale before." The deformation associated with these crustal blocks could also indicate that Venus is still geologically active. "We know that much of Venus has been volcanically resurfaced over time, so some parts of the planet might be really young, geologically speaking," Byrne says. "But several of the jostling blocks have formed in and deformed these young lava plains, which means that the lithosphere fragmented after those plains were laid down. This gives us reason to think that some of these blocks may have moved geologically very recently—perhaps even up to today." The researchers are optimistic that Venus' newly recognized "pack ice" pattern could offer clues to understanding tectonic deformation on planets outside of our solar system, as well as on a much younger Earth. "The thickness of a planet's lithosphere depends mainly upon how hot it is, both in the interior and on the surface," Byrne says. "Heat flow from the young Earth's interior was up to three times greater than it is now, so its lithosphere may have been similar to what we see on Venus today: not thick enough to form plates that subduct, but thick enough to have fragmented into blocks that pushed, pulled, and jostled." NASA and the European Space Agency recently approved three new spacecraft missions to Venus that will acquire observations of the planet's surface at much higher resolution than Magellan. "It's great to see renewed interest in the exploration of Venus, and I'm particularly excited that these missions will be able to test our key finding that the planet's lowlands have fragmented into jostling crustal blocks," Byrne says. The work appears in Proceedings of the National Academy of Sciences. Sean Solomon of Columbia University is co-corresponding author. Richard Ghail of the University of London, Surrey; A. M. Celâl Sengör of Istanbul Technical University; Peter James of Baylor University; and Christian Klimczak of the University of Georgia also contributed to the work. https://phys.org/news/2021-06-ice-tectonics-reveal-venus-geological.html
61 views · Jun 21st
The most severe mass extinction event in the past 540 million years eliminated more than 90 percent of Earth's marine species and 75 percent of terrestrial species. Although scientists had previously hypothesized that the end-Permian mass extinction, which took place 251 million years ago, was triggered by voluminous volcanic eruptions in a region of what is now Siberia, they were not able to explain the mechanism by which the eruptions resulted in the extinction of so many different species, both in the oceans and on land. Associate professor Laura Wasylenki of Northern Arizona University's School of Earth and Sustainability and Department of Chemistry and Biochemistry is co-author on a new paper in Nature Communications entitled, "Nickel isotopes link Siberian Traps aerosol particles to the end-Permian mass extinction," in collaboration with Chinese, Canadian and Swiss scientists. The paper presents the results of nickel isotope analyses performed in Wasylenki's lab on Late Permian sedimentary rocks collected in Arctic Canada. The samples have the lightest nickel isotope ratios ever measured in sedimentary rocks, and the only plausible explanation is that the nickel was sourced from the volcanic terrain, very likely carried by aerosol particles and deposited in the ocean, where it dramatically changed the chemistry of seawater and severely disrupted the marine ecosystem. "The study results provide strong evidence that nickel-rich particles were aerosolized and dispersed widely, both through the atmosphere and into the ocean," Wasylenki said. "Nickel is an essential trace metal for many organisms, but an increase in nickel abundance would have driven an unusual surge in productivity of methanogens, microorganisms that produce methane gas. Increased methane would have been tremendously harmful to all oxygen-dependent life." NAU associate professor Laura Wasylenki is co-author on a new paper in Nature Communications entitled, "Nickel isotopes link Siberian Traps aerosol particles to the end-Permian mass extinction," in collaboration with Chinese, Canadian and Swiss scientists. Credit: Northern Arizona University "Our data provide a direct link between global dispersion of Ni-rich aerosols, ocean chemistry changes and the mass extinction event," Wasylenki said. "The data also demonstrate that environmental degradation likely began well before the extinction event—perhaps starting as early as 300,000 years before then. Prior to this study, the connection between Siberian Traps flood basalt volcanism, marine anoxia and mass extinction was rather vague, but now we have evidence of a specific kill mechanism. This finding demonstrates the power of nickel isotope analyses, which are relatively new, to solve long-standing problems in the geosciences." Wasylenki, who joined NAU in 2018, was formerly an igneous petrologist and then a specialist in calcite crystal growth and biomineralization. She now focuses on the use of metal stable isotope geochemistry to address geological, environmental and biological questions. Many of her recent and current projects have investigated metal isotope effects at solid-fluid interfaces, in particular during metal adsorption to oxyhydroxide mineral particles. This work has implications for ancient and modern geochemical cycles and environmental metal transport. Wasylenki's lab group, named Systematic Experimental Study and Analysis of Metals in the Environment (SESAME Lab), focuses on two main research themes, the cycling of transition metals in modern and ancient oceans and the environmental transport of toxic heavy metals. https://phys.org/news/2021-06-geochemical-end-permian-mass-extinction-event.html
79 views · Jun 21st