For the first time, a unique study conducted at Lund University in Sweden has tracked the meteorite flux to Earth over the past 500 million years. Contrary to current theories, researchers have determined that major collisions in the asteroid belt have not generally affected the number of impacts with Earth to any great extent. Researchers have been studying geological series since the 19th century in order to reconstruct how flora, fauna and the climate have changed over millions of years. Until now, however, almost nothing has been known about ancient meteorite flux—which makes sense since impact is rare, and the battered celestial bodies quickly break down as they encounter Earth's oxygen. A new study published in PNAS shows how researchers in Lund have reconstructed meteorite bombardment towards Earth over the past 500 million years. "The research community previously believed that meteorite flux to Earth was connected to dramatic events in the asteroid belt. The new study, however, shows that the flux has instead been very stable," says Birger Schmitz, professor of geology at Lund University. To conduct the study, researchers at Lund University's Astrogeobiology Laboratory dissolved almost ten tons of sedimentary rocks from ancient seabeds in strong acids because the sediment contains residue from the meteorites dating back to when they fell to Earth. Meteorites contain a small fraction of a mineral, a chromium oxide, which is very resistant to degradation. The microscopic chromium oxide grains were sifted out in the laboratory and serve as time capsules with an abundance of information. "The dissolved sediment represents 15 periods over the past 500 million years. In total, we have extracted chromium oxide from almost 10 000 different meteorites. Chemical analyses then enabled us to determine which types of meteorites the grains represent," says Birger Schmitz. A couple of thousand meteorites land on the Earth's surface every year, and approximately 63 000 space rocks have been documented by science. The space rocks originate from the asteroid belt between Mars and Jupiter where battered celestial bodies from gigantic collisions revolve around the sun. "We were very surprised to learn that only one of the 70 largest asteroid collisions that took place over the past 500 million years resulted in an increased flux of meteorites to Earth. For some reason, most of the rocks stay in the asteroid belt," says Birger Schmitz. The study not only upends generally accepted meteorite flux theories; it also provides entirely new perspectives on which types of celestial bodies are at greatest risk of colliding with Earth and where in the solar system they originate. From a geological time perspective, kilometer-sized celestial bodies collide with the Earth on a regular basis. One such event took place 66 million years ago, when a celestial body stretching over 10 kilometers in size hit the Yucatán Peninsula. The impact was part of the reason the Earth went dark and dinosaurs starved to death. "Future impact from even a small asteroid for example in the sea close to a populated area could lead to disastrous outcomes. This study provides important understanding that we can use to prevent this from happening; for example, by attempting to influence the trajectory of rapidly approaching celestial bodies," concludes Birger Schmitz. https://phys.org/news/2021-06-earth-meteorite-impacts-million-years.html
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Using data from NASA's Orbiting Carbon Observatory 3 (OCO-3) instrument on the International Space Station, researchers have released one of the most accurate maps ever made from space of the human influence on carbon dioxide (CO2) in the Los Angeles metropolitan area. The map shows tiny variations in airborne CO2 from one mile of the giant L.A. Basin to the next. The highest CO2 readings, in yellow on the map, are on the west side of downtown L.A. – a densely populated area with congested freeways and CO2-emitting industries. Yellow indicates atmospheric CO2 elevated by five or more molecules out of every million molecules of air, or five parts per million. That's equivalent to the amount that global atmospheric CO2 is rising globally on average every two years The animation shows five adjoining swaths of data the OCO-3 instrument collected over the metropolitan area to create a map of CO2 concentrations that covers about 50 square miles (80 square kilometers). Each pixel is about 1.3 miles (2.2 kilometers); the color indicates how much higher the concentration of CO2 is in that spot than in clean desert air north of the city (measured at NASA's Armstrong Research Center, upper right). Most of the increasing CO2 in the global atmosphere comes from humans burning fossil fuels for energy, and 70% of that comes from cities. Los Angeles has set goals for cutting its carbon emissions. This type of data can help decisionmakers choose the most effective policies to reach those goals and to measure the effectiveness of new regulations. Data from ground level provides critical local measurements, but satellite data is equally necessary because it covers a wider area and also measures CO2 throughout the entire depth of the atmosphere. This animation shows the accumulation of data from NASA’s OCO-3 instrument used to create a map of carbon dioxide (CO2) concentrations that covers about 50 square miles (80 square kilometers) of the Los Angeles metropolitan area. The highest concentrations are in yellow. Credit: NASA/JPL-Caltech The International Space Station, which hosts the OCO-3 instrument, circles Earth between 52 degrees north and 52 degrees south latitudes—about the latitudes of London and Patagonia. Almost all cities on Earth come within its view on average once every three days. The OCO-3 team at NASA's Jet Propulsion Laboratory in Southern California schedules measurements at up to 40 locations a day. Most of these targets are high-CO2-emitting cities. The instrument consists of a telescope and three spectrometers, a kind of instrument that analyzes wavelengths of the electromagnetic spectrum of sunlight to find the spectral "fingerprint" of carbon dioxide. The telescope swivels rapidly to collect as many adjoining swaths of data as possible over a targeted location within two minutes. OCO-3 usually collects a single swath of data as it orbits, like its predecessor the OCO-2 mission (which is still operating), but it's designed to create snapshot maps like this one to give researchers a more complete picture of emissions from cities and other areas of interest. The maps were published this week in a paper in the journal Remote Sensing of Environment. https://phys.org/news/2021-06-nasa-accurate-space-based-view-la.html
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A huge tornado was spotted as it passed through northern Colorado, with bystanders capturing the funnel in dramatic footage circulating online. The inclement weather caught local meteorologists by surprise, but caused no deaths. The twister touched down near the towns of Platteville and Firestone, both located in Weld County, on Monday evening, moving northeast for several miles before dissipating some 25 minutes later, meteorologist David Barjenbruch told the Denver Post. Videos of the tornado have made the rounds on social media, showing a dark-brown funnel making its way along the landscape from menacing storm clouds above. The storm brought down a number of power lines, which led to at least one home catching fire, according to a local CBS affiliate. Though reports of damage and injuries are still coming in, the Denver National Weather Service said there had been no deaths as of Monday night - among humans, that is, as two livestock animals were reportedly killed. Two residents driving into Firestone as the twister touched down, Kelsey and Cameron Gransee, said they witnessed the path of destruction left in the tornado's wake. "We saw the damage. We saw the debris field. There were trees down, a house on fire; pretty sad," Kelsey told local media. https://www.sott.net/article/453853-Tornado-touches-down-in-Weld-County-Colorado
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A huge tornado was spotted as it passed through northern Colorado, with bystanders capturing the funnel in dramatic footage circulating online. The inclement weather caught local meteorologists by surprise, but caused no deaths. The twister touched down near the towns of Platteville and Firestone, both located in Weld County, on Monday evening, moving northeast for several miles before dissipating some 25 minutes later, meteorologist David Barjenbruch told the Denver Post. Videos of the tornado have made the rounds on social media, showing a dark-brown funnel making its way along the landscape from menacing storm clouds above. The storm brought down a number of power lines, which led to at least one home catching fire, according to a local CBS affiliate. Though reports of damage and injuries are still coming in, the Denver National Weather Service said there had been no deaths as of Monday night - among humans, that is, as two livestock animals were reportedly killed. Two residents driving into Firestone as the twister touched down, Kelsey and Cameron Gransee, said they witnessed the path of destruction left in the tornado's wake. "We saw the damage. We saw the debris field. There were trees down, a house on fire; pretty sad," Kelsey told local media. https://www.sott.net/article/453853-Tornado-touches-down-in-Weld-County-Colorado
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