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  • richardmitnick 11:48 pm on February 16, 2021 Permalink | Reply
    Tags: "Important Climate Change Mystery Solved by Scientists", A long-standing mystery called the “Holocene temperature conundrum”, , , Marine and Coastal Sciences, Planetary Sciences, Revised Holocene temperature record affirms role of greenhouse gases in recent millennia., , Scientists have resolved a key climate change mystery showing that the annual global temperature today is the warmest of the past 10000 years., Scientists used marine fossils to reconstruct the temperature histories of the two most recent warm intervals on Earth., The late Holocene warming was indeed caused by the increase in greenhouse gases.   

    From Rutgers University: “Important Climate Change Mystery Solved by Scientists” 

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    From Rutgers University

    February 16, 2021
    Todd Bates
    todd.bates@rutgers.edu

    Revised Holocene temperature record affirms role of greenhouse gases in recent millennia.

    1
    Rutgers scientists aboard the R/V JOIDES Resolution on International Ocean Discovery Program Expedition 363 in 2016, including (left to right) Gregory Mountain, Tali Babila, Samantha Bova and Yair Rosenthal. Credit: IODP-Jodes Resolution Science Operator.

    Scientists have resolved a key climate change mystery, showing that the annual global temperature today is the warmest of the past 10,000 years – contrary to recent research, according to a Rutgers-led study in the journal Nature.

    The long-standing mystery is called the “Holocene temperature conundrum,” with some skeptics contending that climate model predictions of future warming must be wrong. The scientists say their findings will challenge long-held views on the temperature history in the Holocene era, which began about 12,000 years ago.

    “Our reconstruction shows that the first half of the Holocene was colder than in industrial times due to the cooling effects of remnant ice sheets from the previous glacial period – contrary to previous reconstructions of global temperatures,” said lead author Samantha Bova, a postdoctoral researcher associate in the lab of co-author Yair Rosenthal, a Distinguished Professor in the Department of Marine and Coastal Sciences and Department of Earth and Planetary Sciences at Rutgers University–New Brunswick. “The late Holocene warming was indeed caused by the increase in greenhouse gases, as predicted by climate models, and that eliminates any doubts about the key role of carbon dioxide in global warming.”

    2
    This image shows the evolution of temperature during the Holocene era and some of the key mechanisms responsible for the increase in temperature over the last 12,000 years. Credit: Samantha Bova.

    Scientists used marine calcareous (calcium carbonate-containing) fossils from foraminifers – single-celled organisms that live at the ocean surface – to reconstruct the temperature histories of the two most recent warm intervals on Earth. They are the Last Interglacial period from 128,000 to 115,000 years ago and the Holocene. To get the fossils, the scientists collected a core of bottom sediments near the mouth of the Sepik River off northern Papua New Guinea during the Rutgers-led Expedition 363 of the International Ocean Discovery Program. The core features rapidly accumulating sediments that allowed the scientists to recreate the temperature history of the western Pacific warm pool, which closely tracks changes in global temperatures.

    How temperature evolved during the Last Interglacial and Holocene eras is controversial. Some data suggest that the average annual global temperature during modern times does not exceed the warmth in the Holocene’s early warm period, called the “Holocene thermal maximum,” which was followed by global cooling. Meanwhile, climate models strongly suggest that global temperatures have risen throughout the past 10,000 years.

    “The apparent discrepancy between climate models and data has cast doubts among skeptics about the role of greenhouse gases in climate change during the Holocene and possibly in the future,” Rosenthal said. “We found that post-industrial warming has indeed accelerated the long and steady trend of warming throughout the past 10,000 years. Our study also underscores the importance of seasonal changes, specifically Northern Hemisphere summers, in driving many climate systems. Our method can, for the first time, use seasonal temperatures to come up with annual averages.”

    Rutgers-affiliated co-authors include Shital P. Godad, a former Rutgers researcher now at National Taiwan University (TW). Scientists at The Ohio State University (US) and Nanjing Normal University (CN) contributed to the study.

    See the full article here .


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  • richardmitnick 9:02 am on September 20, 2020 Permalink | Reply
    Tags: "A new view of Enceladus", , , , , , Planetary Sciences   

    From European Space Agency – United Space in Europe: “A new view of Enceladus” 

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    From European Space Agency – United Space in Europe

    18/09/2020

    1
    Saturn’s moon Enceladus. Credit NASA/ESA/ASI Cassini-Huygens team.

    A global infrared mosaic of Saturn’s moon Enceladus created using a complete dataset from the Cassini spacecraft has revealed new detail on the moon’s surface.

    NASA/ESA/ASI Cassini-Huygens Spacecraft.

    Cassini orbited Saturn and its moons from 2004 to 2017. The mission ended when the spacecraft was intentionally plunged into the planet’s atmosphere, but new discoveries are still being made with the data.

    During the mission lifetime, Cassini flew by Enceladus 147 times, with 23 close encounters of the icy moon. The Visual and Infrared Mapping Spectrometer (VIMS) collected data that can be used to reveal information on the temperature and composition of the surface, as well as the sizes and crystallinity of ice grains.

    VIMS instrument on NASA/ESA/ASI Cassini-Huygens spacecraft.

    A study published in Icarus has produced a global spectral mosaic using the complete VIMS dataset. The full-colour images were created by combining three IR channels of the VIMS spectro-imager, represented here by red, green, and blue colours, and overlapping these on a mosaic created using the Imaging Science Subsystem on Cassini by another team.

    The image shows five infrared views of Enceladus centred on the leading side, the Saturn-facing side, and the trailing side in the top row, and the North and South Pole in the bottom row. Click here for an annotated version. The globe can also be explored interactively.

    The scientists used a photometric correction to reveal new details on the surface of the moon. Enceladus has a surface composed almost of pure water ice, which makes it highly reflective, but the observed brightness depends on the properties of the surface material, the surface shape, and the angle at which it is viewed. Correcting for these variations was necessary to show the differences in composition and physical state at the surface.

    By using these improved photometric corrections, the scientists have been able to reveal spectral variations which correspond to the different colours in the images. These are particularly striking in the region with four large tectonic faults known as the Tiger Stripes at the South Pole. The image of the South Pole also reveals a clear boundary between terrains where the light red colour meets the blue region. The smooth red colour seen in the first image is likely due to recently exposed freshwater ice. This could be the surface signature of hotspots on the seafloor.

    In the future the scientists plan to apply their technique to other icy moons to compare them with Enceladus. Similar infrared mapping by the Juice and Europa Clipper missions will be able to detect recent activity on Jupiter’s moons Europa and Ganymede.

    See the full article here .


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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 10:27 am on August 12, 2020 Permalink | Reply
    Tags: "Lava oceans may not explain the brightness of some hot super-Earths", "Lava-ocean planets", , Hot super-Earths are between one and 10 times the mass of Earth and have extremely short orbital periods., Making their own lava and cooled glass., Metal-rich atmospheres and highly reflective clouds contribute to the brightness., , Planetary Sciences   

    From MIT News: “Lava oceans may not explain the brightness of some hot super-Earths” 

    MIT News

    From MIT News

    August 4, 2020
    Jennifer Chu

    1
    Molten lava in crucible placed under experimental setup. Setup includes a spectrometer (right) which measures the light from the lava at different wavelengths. Image: Tajana Schneiderman.

    By making their own lava and cooled glass, scientists find these materials likely aren’t responsible for the unexpected glow of some exoplanets.

    Arguably some of the weirdest, most extreme planets among the more than 4,000 exoplanets discovered to date are the hot super-Earths — rocky, flaming-hot worlds that zing so precariously close to their host stars that some of their surfaces are likely melted seas of molten lava.

    These fiery worlds, about the size of Earth, are known more evocatively as “lava-ocean planets,” and scientists have observed that a handful of these hot super-Earths are unusually bright, and in fact brighter than our own brilliant blue planet.

    Exactly why these far-off fireballs are so bright is unclear, but new experimental evidence by scientists at MIT shows that the unexpected glow from these worlds is likely not due to either molten lava or cooled glass (i.e. rapidly solidified lava) on their surfaces.

    The researchers came to this conclusion after interrogating the problem in a refreshingly direct way: melting rocks in a furnace and measuring the brightness of the resulting lava and cooled glass, which they then used to calculate the brightness of regions of a planet covered in molten or solidified material. Their results revealed that lava and glass, at least as a product of the materials they melted in the lab, are not reflective enough to explain the observed brightness of certain lava-ocean planets.

    Their findings suggest that hot super-Earths may have other surprising features that contribute to their brightness, such as metal-rich atmospheres and highly reflective clouds.

    “We still have so much to understand about these lava-ocean planets,” says Zahra Essack, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences. “We thought of them as just glowing balls of rock, but these planets may have complex systems of surface and atmospheric processes that are quite exotic, and not anything we’ve ever seen before.”

    Essack is the first author of a study detailing the team’s results, which appears today in The Astrophysical Journal. Her co-authors are former MIT postdoc Mihkel Pajusalu, who was instrumental in the experiment’s initial setup, and Sara Seager, the Class of 1941 Professor of Planetary Science, with appointments in the departments of Physics and Aeronautics and Astronautics.

    More than charcoal balls

    Hot super-Earths are between one and 10 times the mass of Earth, and have extremely short orbital periods, circling their host star in just 10 days or less. Scientists have expected that these lava worlds would be so close to their host star that any appreciable atmosphere and clouds would be stripped away. Their surfaces as a result would be at least 850 kelvins, or 1,070 degrees Fahrenheit — hot enough to cover the surface in oceans of molten rock.

    Scientists have previously discovered a handful of super-Earths with unexpectedly high albedos, or brightnesses, in which they reflected between 40 and 50 percent of the light from their star. In comparison, the Earth’s albedo, with all of its reflective surfaces and clouds, is only around 30 percent.

    “You’d expect these lava planets to be sort of charcoal balls orbiting in space — very dark, not very bright at all,” Essack says. “So what makes them so bright?”

    One idea has been that the lava itself may be the main source of the planets’ luminosity, though there had never been any proof, either in observations or experiments.

    “So being MIT people, we decided, O.K., we should make some lava and see if it’s bright or not,” Essack says.

    Making lava

    To first make lava, the team needed a furnace that could reach temperatures high enough to melt basalt and feldspar, the two rock types that they chose for their experiments, as they are well-characterized material that are common on Earth.

    As it turns out, they initially didn’t have to look farther than the foundry at MIT, a space within the Department of Materials Science and Engineering, where trained metallurgists help students and researchers melt materials in the foundry’s furnace for research and class projects.

    Essack brought samples of feldspar to the foundry, where metallurgists determined the type of crucible in which to place them, and the temperatures at which they needed to be heated.

    “They drop it in the furnace, let the rocks melt, take it out, and then the whole place turns into a furnace itself — it’s very hot,” Essack says. “And it was an incredible experience to stand next to this bright glowing lava, feeling that heat.”

    However, the experiment quickly ran up against an obstacle: The lava, once it was pulled from the furnace, almost instantly cooled into a smooth, glassy material. The process occurred so quickly that Essack wasn’t able to measure the lava’s reflectivity while still molten.

    So she took the cooled feldspar glass to a spectroscopy lab she designed and implemented on campus to measure its reflectance, by shining a light on the glass from different angles and measuring the amount of light reflecting back from the surface. She repeated these experiments for cooled basalt glass, samples of which were donated by colleagues at Syracuse University who run the Lava Project. Seager visited them a few years ago for a preliminary version of the experiment, and at that time collected basalt samples now used for Essack’s experiments.

    “They melted a huge bunch of basalt and poured it down a slope, and they chipped it up for us,” Seager says.

    After measuring the brightness of cooled basalt and feldspar glass, Essack looked through the literature to find reflectivity measurements of molten silicates, which are a major component of lava on Earth. She used these measurements as a reference to calculate how bright the initial lava from the basalt and feldspar glass would be. She then estimated the brightness of a hot super-Earth covered either entirely in lava or cooled glass, or combinations of the two materials.

    In the end, she found that, no matter the combination of surface materials, the albedo of a lava-ocean planet would be no more than about 10 percent — pretty dark compared with the 40 to 50 percent albedo observed for some hot super-Earths.

    “This is quite dark compared to Earth, and not enough to explain the brightness of the planets we were interested in,” Essack says.

    This realization has narrowed the search range for interpreting observations, and directs future studies to consider other exotic possibilities, such as the presence of atmospheres rich in reflective metals.

    “We’re not 100 percent sure what these planets are made of, so we’re narrowing the parameter space and guiding future studies toward all these other potential options,” Essack says.

    This research was funded, in part, by NASA’s TESS mission and, in part, by the MIT Presidential Fellowship.

    NASA/MIT TESS replaced Kepler in search for exoplanets

    See the full article here .


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