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News Article | May 17, 2017
Site: www.eurekalert.org

Our Cold War history is now offering scientists a chance to better understand the complex space system that surrounds us. Space weather -- which can include changes in Earth's magnetic environment -- are usually triggered by the sun's activity, but recently declassified data on high-altitude nuclear explosion tests have provided a new look at the mechansisms that set off perturbations in that magnetic system. Such information can help support NASA's efforts to protect satellites and astronauts from the natural radiation inherent in space. From 1958 to 1962, the U.S. and U.S.S.R. ran high-altitude tests with exotic code names like Starfish, Argus and Teak. The tests have long since ended, and the goals at the time were military. Today, however, they can provide crucial information on how humans can affect space. The tests, and other human-induced space weather, are the focus of a comprehensive new study published in Space Science Reviews. "The tests were a human-generated and extreme example of some of the space weather effects frequently caused by the sun," said Phil Erickson, assistant director at MIT's Haystack Observatory, Westford, Massachusetts, and co-author on the paper. "If we understand what happened in the somewhat controlled and extreme event that was caused by one of these man-made events, we can more easily understand the natural variation in the near-space environment." By and large, space weather ? which affects the region of near-Earth space where astronauts and satellites travel ? is typically driven by external factors. The sun sends out millions of high-energy particles, the solar wind, which races out across the solar system before encountering Earth and its magnetosphere, a protective magnetic field surrounding the planet. Most of the charged particles are deflected, but some make their way into near-Earth space and can impact our satellites by damaging onboard electronics and disrupting communications or navigation signals. These particles, along with electromagnetic energy that accompanies them, can also cause auroras, while changes in the magnetic field can induce currents that damage power grids. The Cold War tests, which detonated explosives at heights from 16 to 250 miles above the surface, mimicked some of these natural effects. Upon detonation, a first blast wave expelled an expanding fireball of plasma, a hot gas of electrically charged particles. This created a geomagnetic disturbance, which distorted Earth's magnetic field lines and induced an electric field on the surface. Some of the tests even created artificial radiation belts, akin to the natural Van Allen radiation belts, a layer of charged particles held in place by Earth's magnetic fields. The artificially trapped charged particles remained in significant numbers for weeks, and in one case, years. These particles, natural and artificial, can affect electronics on high-flying satellites -- in fact some failed as a result of the tests. Although the induced radiation belts were physically similar to Earth's natural radiation belts, their trapped particles had different energies. By comparing the energies of the particles, it is possible to distinguish the fission-generated particles and those naturally occurring in the Van Allen belts. Other tests mimicked other natural phenomena we see in space. The Teak test, which took place on Aug. 1, 1958, was notable for the artificial aurora that resulted. The test was conducted over Johnston Island in the Pacific Ocean. On the same day, the Apia Observatory in Western Samoa observed a highly unusual aurora, which are typically only observed in at the poles. The energetic particles released by the test likely followed Earth's magnetic field lines to the Polynesian island nation, inducing the aurora. Observing how the tests caused aurora, can provide insight into what the natural auroral mechanisms are too. Later that same year, when the Argus tests were conducted, effects were seen around the world. These tests were conducted at higher altitudes than previous tests, allowing the particles to travel farther around Earth. Sudden geomagnetic storms were observed from Sweden to Arizona and scientists used the observed time of the events to determine the speed at which the particles from the explosion traveled. They observed two high-speed waves: the first travelled at 1,860 miles per second and the second, less than a fourth that speed. Unlike the artificial radiation belts, these geomagnetic effects were short-lived, lasting only seconds. Atmospheric nuclear testing has long since stopped, and the present space environment remains dominated by natural phenomena. However, considering such historical events allows scientists and engineers to understand the effects of space weather on our infrastructure and technical systems. Such information adds to a larger body of heliophysics research, which studies our near-Earth space environment in order to better understand the natural causes of space weather. NASA missions such as Magnetospheric Multiscale (MMS), Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms (THEMIS) study Earth's magnetosphere and the causes of space weather. Other NASA missions, like STEREO, constantly survey the sun to look for activity that could trigger space weather. These missions help inform scientists about the complex system we live in, and how to protect the satellites we utilize for communication and navigation on a daily basis.


News Article | May 17, 2017
Site: phys.org

From 1958 to 1962, the U.S. and U.S.S.R. ran high-altitude tests with exotic code names like Starfish, Argus and Teak. The tests have long since ended, and the goals at the time were military. Today, however, they can provide crucial information on how humans can affect space. The tests, and other human-induced space weather, are the focus of a comprehensive new study published in Space Science Reviews. "The tests were a human-generated and extreme example of some of the space weather effects frequently caused by the sun," said Phil Erickson, assistant director at MIT's Haystack Observatory, Westford, Massachusetts, and co-author on the paper. "If we understand what happened in the somewhat controlled and extreme event that was caused by one of these man-made events, we can more easily understand the natural variation in the near-space environment." By and large, space weather ? which affects the region of near-Earth space where astronauts and satellites travel ? is typically driven by external factors. The sun sends out millions of high-energy particles, the solar wind, which races out across the solar system before encountering Earth and its magnetosphere, a protective magnetic field surrounding the planet. Most of the charged particles are deflected, but some make their way into near-Earth space and can impact our satellites by damaging onboard electronics and disrupting communications or navigation signals. These particles, along with electromagnetic energy that accompanies them, can also cause auroras, while changes in the magnetic field can induce currents that damage power grids. The Cold War tests, which detonated explosives at heights from 16 to 250 miles above the surface, mimicked some of these natural effects. Upon detonation, a first blast wave expelled an expanding fireball of plasma, a hot gas of electrically charged particles. This created a geomagnetic disturbance, which distorted Earth's magnetic field lines and induced an electric field on the surface. Some of the tests even created artificial radiation belts, akin to the natural Van Allen radiation belts, a layer of charged particles held in place by Earth's magnetic fields. The artificially trapped charged particles remained in significant numbers for weeks, and in one case, years. These particles, natural and artificial, can affect electronics on high-flying satellites—in fact some failed as a result of the tests. Although the induced radiation belts were physically similar to Earth's natural radiation belts, their trapped particles had different energies. By comparing the energies of the particles, it is possible to distinguish the fission-generated particles and those naturally occurring in the Van Allen belts. Other tests mimicked other natural phenomena we see in space. The Teak test, which took place on Aug. 1, 1958, was notable for the artificial aurora that resulted. The test was conducted over Johnston Island in the Pacific Ocean. On the same day, the Apia Observatory in Western Samoa observed a highly unusual aurora, which are typically only observed in at the poles. The energetic particles released by the test likely followed Earth's magnetic field lines to the Polynesian island nation, inducing the aurora. Observing how the tests caused aurora, can provide insight into what the natural auroral mechanisms are too. Later that same year, when the Argus tests were conducted, effects were seen around the world. These tests were conducted at higher altitudes than previous tests, allowing the particles to travel farther around Earth. Sudden geomagnetic storms were observed from Sweden to Arizona and scientists used the observed time of the events to determine the speed at which the particles from the explosion traveled. They observed two high-speed waves: the first travelled at 1,860 miles per second and the second, less than a fourth that speed. Unlike the artificial radiation belts, these geomagnetic effects were short-lived, lasting only seconds. Atmospheric nuclear testing has long since stopped, and the present space environment remains dominated by natural phenomena. However, considering such historical events allows scientists and engineers to understand the effects of space weather on our infrastructure and technical systems. Such information adds to a larger body of heliophysics research, which studies our near-Earth space environment in order to better understand the natural causes of space weather. NASA missions such as Magnetospheric Multiscale (MMS), Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms (THEMIS) study Earth's magnetosphere and the causes of space weather. Other NASA missions, like STEREO, constantly survey the sun to look for activity that could trigger space weather. These missions help inform scientists about the complex system we live in, and how to protect the satellites we utilize for communication and navigation on a daily basis.


News Article | May 18, 2017
Site: www.chromatographytechniques.com

Our Cold War history is now offering scientists a chance to better understand the complex space system that surrounds us. Space weather — which can include changes in Earth's magnetic environment — are usually triggered by the sun’s activity, but recently declassified data on high-altitude nuclear explosion tests have provided a new look at the mechanisms that set off perturbations in that magnetic system. Such information can help support NASA’s efforts to protect satellites and astronauts from the natural radiation inherent in space. From 1958 to 1962, the U.S. and U.S.S.R. ran high-altitude tests with exotic code names like Starfish, Argus and Teak. The tests have long since ended, and the goals at the time were military. Today, however, they can provide crucial information on how humans can affect space. The tests, and other human-induced space weather, are the focus of a comprehensive new study published in Space Science Reviews. “The tests were a human-generated and extreme example of some of the space weather effects frequently caused by the sun,” said Phil Erickson, assistant director at MIT’s Haystack Observatory, Westford, Massachusetts, and co-author on the paper. “If we understand what happened in the somewhat controlled and extreme event that was caused by one of these man-made events, we can more easily understand the natural variation in the near-space environment.” By and large, space weather — which affects the region of near-Earth space where astronauts and satellites travel — is typically driven by external factors. The sun sends out millions of high-energy particles, the solar wind, which races out across the solar system before encountering Earth and its magnetosphere, a protective magnetic field surrounding the planet. Most of the charged particles are deflected, but some make their way into near-Earth space and can impact our satellites by damaging onboard electronics and disrupting communications or navigation signals. These particles, along with electromagnetic energy that accompanies them, can also cause auroras, while changes in the magnetic field can induce currents that damage power grids. The Cold War tests, which detonated explosives at heights from 16 to 250 miles above the surface, mimicked some of these natural effects. Upon detonation, a first blast wave expelled an expanding fireball of plasma, a hot gas of electrically charged particles. This created a geomagnetic disturbance, which distorted Earth’s magnetic field lines and induced an electric field on the surface. Some of the tests even created artificial radiation belts, akin to the natural Van Allen radiation belts, a layer of charged particles held in place by Earth’s magnetic fields. The artificially trapped charged particles remained in significant numbers for weeks, and in one case, years. These particles, natural and artificial, can affect electronics on high-flying satellites — in fact some failed as a result of the tests. Although the induced radiation belts were physically similar to Earth’s natural radiation belts, their trapped particles had different energies. By comparing the energies of the particles, it is possible to distinguish the fission-generated particles and those naturally occurring in the Van Allen belts. Other tests mimicked other natural phenomena we see in space. The Teak test, which took place on Aug. 1, 1958, was notable for the artificial aurora that resulted. The test was conducted over Johnston Island in the Pacific Ocean. On the same day, the Apia Observatory in Western Samoa observed a highly unusual aurora, which are typically only observed in at the poles. The energetic particles released by the test likely followed Earth’s magnetic field lines to the Polynesian island nation, inducing the aurora. Observing how the tests caused aurora, can provide insight into what the natural auroral mechanisms are too. Later that same year, when the Argus tests were conducted, effects were seen around the world. These tests were conducted at higher altitudes than previous tests, allowing the particles to travel farther around Earth. Sudden geomagnetic storms were observed from Sweden to Arizona and scientists used the observed time of the events to determine the speed at which the particles from the explosion traveled. They observed two high-speed waves: the first traveled at 1,860 miles per second and the second, less than a fourth that speed. Unlike the artificial radiation belts, these geomagnetic effects were short-lived, lasting only seconds. Such atmospheric nuclear testing has long since stopped, and the present space environment remains dominated by natural phenomena. However, considering such historical events allows scientists and engineers to understand the effects of space weather on our infrastructure and technical systems. Such information adds to a larger body of heliophysics research, which studies our near-Earth space environment in order to better understand the natural causes of space weather. NASA missions such as Magnetospheric Multiscale (MMS), Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms (THEMIS) study Earth’s magnetosphere and the causes of space weather. Other NASA missions, like STEREO, constantly survey the sun to look for activity that could trigger space weather. These missions help inform scientists about the complex system we live in, and how to protect the satellites we utilize for communication and navigation on a daily basis.


News Article | May 11, 2017
Site: www.eurekalert.org

PROVIDENCE, R.I. [Brown University] -- In looking at NASA images of Mars a few years ago, Brown University geologist Peter Schultz noticed sets of strange bright streaks emanating from a few large-impact craters on the planet's surface. The streaks are odd in that they extend much farther from the craters than normal ejecta patterns, and they are only visible in thermal infrared images taken during the Martian night. Using geological observation, laboratory impact experiments and computer modeling, Schultz and Brown graduate student Stephanie Quintana have offered a new explanation for how those streaks were formed. They show that tornado-like wind vortices -- generated by crater-forming impacts and swirling at 500 miles per hour or more -- scoured the surface and blasted away dust and small rocks to expose the blockier surfaces beneath. "This would be like an F8 tornado sweeping across the surface," Schultz said. "These are winds on Mars that will never be seen again unless another impact." The research is published online in the journal Icarus. Schultz says he first saw the streaks during one of his "tours of Mars." In his downtime between projects, he pulls up random images from NASA's orbital spacecraft just to see if he might spot something interesting. In this case, he was looking at infrared images taken during the Martian nighttime by the THEMIS instrument, which flies aboard the Mars Odyssey orbiter. The infrared images capture contrasts in heat retention on the surface. Brighter regions at night indicate surfaces that retain more heat from the previous day than surrounding surfaces, just as grassy fields cool off at night while buildings in the city remain warmer. "You couldn't see these things at all in visible wavelength images, but in the nighttime infrared they're very bright," Schultz said. "Brightness in the infrared indicates blocky surfaces, which retain more heat than surfaces covered by powder and debris. That tells us that something came along and scoured those surfaces bare." And Schultz had an idea what that something might be. He has been studying impacts and impact processes for years using NASA's Vertical Gun Range, a high-powered cannon that can fire projectiles at speeds up to 15,000 miles per hour. "We had been seeing some things in experiments we thought might cause these streaks," he said. When an asteroid or other body strikes a planet at high speed, tons of material from both the impactor and the target surface are instantly vaporized. Schultz's experiments showed that vapor plumes travel outward from an impact point, just above the impact surface, at incredible speeds. Scaling laboratory impacts to the size of those on Mars, a vapor plume's speed would be supersonic. And it would interact with the Martian atmosphere to generate powerful winds. The plume and its associated winds on their own didn't cause the strange streaks, however. The plumes generally travel just above the surface, which prevents the kind of deep scouring seen in the streaked areas. But Schultz and Quintana showed that when the plume strikes a raised surface feature, it disturbs the flow and causes powerful tornadic vortices to form and drop to the surface. And those vortices, the researchers say, are responsible for scouring the narrow streaks. Schultz and Quintana showed that the streaks are nearly always seen in conjunction with raised surface features. Very often, for example, they are associated with the raised ridges of smaller impact craters that were already in place when the larger impact occurred. As the plume raced outward from the larger impact, it encountered the small crater rim, leaving bright twin streaks on the downwind side. "Where these vortices encounter the surface, they sweep away the small particles that sit loose on the surface, exposing the bigger blocky material underneath, and that's what gives us these streaks," Schultz said. Schultz says the streaks could prove useful in establishing rates of erosion and dust deposition in areas where the streaks are found. "We know these formed at the same time as these large craters, and we can date the age of the craters," Schultz said. "So now we have a template for looking at erosion." But with more research, the streaks could eventually reveal much more than that. From a preliminary survey of the planet, the researchers say the streaks appear to form around craters in the ballpark of 20 kilometers across. But they don't appear in all such craters. Why they form in some places and not others could provide information about the Martian surface at the time of the impact. The researchers' experiments reveal that the presence of volatile compounds -- a thick layer of water ice on the surface or subsurface, for example -- affect the amount the vapor that rushes out from an impact. So in that way, the streaks might serve as indicators of whether ice may have been present at the time of an impact, which could lend insight into reconstructions of past climate on Mars. Equally possible, the streaks could be related to the composition of the impactor, such as rare collisions by high-volatile objects, such as comets. "The next step is to really dig into the conditions that cause the streaks," Schultz said. "They may have a lot to tell us, so stay tuned."


News Article | May 12, 2017
Site: www.chromatographytechniques.com

Looking at NASA images of Mars a few years ago, Brown University geologist Peter Schultz noticed sets of strange bright streaks emanating from a few large-impact craters on the planet’s surface. The streaks are odd in that they extend much farther from the craters than normal ejecta patterns, and they are only visible in thermal infrared images taken during the Martian night. Using geological observation, laboratory impact experiments and computer modeling of impact processes, Schultz and Brown graduate student Stephanie Quintana have offered a new explanation for how those streaks were formed. The researchers show that tornado-like wind vortices — generated by crater-forming impacts and swirling at 500 miles per hour or more — scoured the surface and blasted away dust and small rocks to expose the blockier surfaces beneath. “This would be like an F8 tornado sweeping across the surface,” Schultz said. “These are winds on Mars that will never be seen again unless another impact.” The research is published online in the journal Icarus. Schultz says he first saw the streaks during one of his “tours of Mars.” In his downtime between projects, he pulls up random images from NASA’s orbital spacecraft just to see if he might spot something interesting. In this case, he was looking at infrared images taken during the Martian nighttime by the THEMIS instrument, which flies aboard the Mars Odyssey orbiter. The infrared images capture contrasts in heat retention on the surface. Brighter regions at night indicate surfaces that retain more heat from the previous day than surrounding surfaces, just as grassy fields cool off at night while buildings in the city remain warmer. “You couldn’t see these things at all in visible wavelength images, but in the nighttime infrared they’re very bright,” Schultz said. “Brightness in the infrared indicates blocky surfaces, which retain more heat than surfaces covered by powder and debris. That tells us that something came along and scoured those surfaces bare.” And Schultz had an idea what that something might be. He has been studying impacts and impact processes for years using NASA’s Vertical Gun Range, a high-powered cannon that can fire projectiles at speeds up to 15,000 miles per hour. “We had been seeing some things in experiments we thought might cause these streaks,” he said. When an asteroid or other body strikes a planet at high speed, tons of material from both the impactor and the target surface are instantly vaporized. Schultz’s experiments showed that vapor plumes travel outward from an impact point, just above the impact surface, at incredible speeds. Scaling laboratory impacts to the size of those on Mars, a vapor plume’s speed would be supersonic. And it would interact with the Martian atmosphere to generate powerful winds. The plume and its associated winds on their own didn’t cause the strange streaks, however. The plumes generally travel just above the surface, which prevents the kind of deep scouring seen in the streaked areas. But Schultz and Quintana showed that when the plume strikes a raised surface feature, it disturbs the flow and causes powerful tornadic vortices to form and drop to the surface. And those vortices, the researchers say, are responsible for scouring the narrow streaks. Schultz and Quintana showed that the streaks are nearly always seen in conjunction with raised surface features. Very often, for example, they are associated with the raised ridges of smaller impact craters that were already in place when the larger impact occurred. As the plume raced outward from the larger impact, it encountered the small crater rim, leaving bright twin streaks on the downwind side. “Where these vortices encounter the surface, they sweep away the small particles that sit loose on the surface, exposing the bigger blocky material underneath, and that’s what gives us these streaks,” Schultz said. Schultz says the streaks could prove useful in establishing rates of erosion and dust deposition in areas where the streaks are found. “We know these formed at the same time as these large craters, and we can date the age of the craters,” Schultz said. “So now we have a template for looking at erosion.” But with more research, the streaks could eventually reveal much more than that. From a preliminary survey of the planet, the researchers say the streaks appear to form around craters in the ballpark of 20 kilometers across. But they don’t appear in all such craters. Why they form in some places and not others could provide information about the Martian surface at the time of the impact. The researchers’ experiments reveal that the presence of volatile compounds — a thick layer of water ice on the surface or subsurface, for example — affect the amount the vapor that rushes out from an impact. So in that way, the streaks might serve as indicators of whether ice may have been present at the time of an impact, which could lend insight into reconstructions of past climate on Mars. Equally possible, the streaks could be related to the composition of the impactor, such as rare collisions by high-volatile objects, such as comets. “The next step is to really dig into the conditions that cause the streaks,” Schultz said. “They may have a lot to tell us, so stay tuned.”


News Article | May 12, 2017
Site: www.chromatographytechniques.com

Looking at NASA images of Mars a few years ago, Brown University geologist Peter Schultz noticed sets of strange bright streaks emanating from a few large-impact craters on the planet’s surface. The streaks are odd in that they extend much farther from the craters than normal ejecta patterns, and they are only visible in thermal infrared images taken during the Martian night. Using geological observation, laboratory impact experiments and computer modeling of impact processes, Schultz and Brown graduate student Stephanie Quintana have offered a new explanation for how those streaks were formed. The researchers show that tornado-like wind vortices — generated by crater-forming impacts and swirling at 500 miles per hour or more — scoured the surface and blasted away dust and small rocks to expose the blockier surfaces beneath. “This would be like an F8 tornado sweeping across the surface,” Schultz said. “These are winds on Mars that will never be seen again unless another impact.” The research is published online in the journal Icarus. Schultz says he first saw the streaks during one of his “tours of Mars.” In his downtime between projects, he pulls up random images from NASA’s orbital spacecraft just to see if he might spot something interesting. In this case, he was looking at infrared images taken during the Martian nighttime by the THEMIS instrument, which flies aboard the Mars Odyssey orbiter. The infrared images capture contrasts in heat retention on the surface. Brighter regions at night indicate surfaces that retain more heat from the previous day than surrounding surfaces, just as grassy fields cool off at night while buildings in the city remain warmer. “You couldn’t see these things at all in visible wavelength images, but in the nighttime infrared they’re very bright,” Schultz said. “Brightness in the infrared indicates blocky surfaces, which retain more heat than surfaces covered by powder and debris. That tells us that something came along and scoured those surfaces bare.” And Schultz had an idea what that something might be. He has been studying impacts and impact processes for years using NASA’s Vertical Gun Range, a high-powered cannon that can fire projectiles at speeds up to 15,000 miles per hour. “We had been seeing some things in experiments we thought might cause these streaks,” he said. When an asteroid or other body strikes a planet at high speed, tons of material from both the impactor and the target surface are instantly vaporized. Schultz’s experiments showed that vapor plumes travel outward from an impact point, just above the impact surface, at incredible speeds. Scaling laboratory impacts to the size of those on Mars, a vapor plume’s speed would be supersonic. And it would interact with the Martian atmosphere to generate powerful winds. The plume and its associated winds on their own didn’t cause the strange streaks, however. The plumes generally travel just above the surface, which prevents the kind of deep scouring seen in the streaked areas. But Schultz and Quintana showed that when the plume strikes a raised surface feature, it disturbs the flow and causes powerful tornadic vortices to form and drop to the surface. And those vortices, the researchers say, are responsible for scouring the narrow streaks. Schultz and Quintana showed that the streaks are nearly always seen in conjunction with raised surface features. Very often, for example, they are associated with the raised ridges of smaller impact craters that were already in place when the larger impact occurred. As the plume raced outward from the larger impact, it encountered the small crater rim, leaving bright twin streaks on the downwind side. “Where these vortices encounter the surface, they sweep away the small particles that sit loose on the surface, exposing the bigger blocky material underneath, and that’s what gives us these streaks,” Schultz said. Schultz says the streaks could prove useful in establishing rates of erosion and dust deposition in areas where the streaks are found. “We know these formed at the same time as these large craters, and we can date the age of the craters,” Schultz said. “So now we have a template for looking at erosion.” But with more research, the streaks could eventually reveal much more than that. From a preliminary survey of the planet, the researchers say the streaks appear to form around craters in the ballpark of 20 kilometers across. But they don’t appear in all such craters. Why they form in some places and not others could provide information about the Martian surface at the time of the impact. The researchers’ experiments reveal that the presence of volatile compounds — a thick layer of water ice on the surface or subsurface, for example — affect the amount the vapor that rushes out from an impact. So in that way, the streaks might serve as indicators of whether ice may have been present at the time of an impact, which could lend insight into reconstructions of past climate on Mars. Equally possible, the streaks could be related to the composition of the impactor, such as rare collisions by high-volatile objects, such as comets. “The next step is to really dig into the conditions that cause the streaks,” Schultz said. “They may have a lot to tell us, so stay tuned.”


Using geological observation, laboratory impact experiments and computer modeling, Schultz and Brown graduate student Stephanie Quintana have offered a new explanation for how those streaks were formed. They show that tornado-like wind vortices—generated by crater-forming impacts and swirling at 500 miles per hour or more—scoured the surface and blasted away dust and small rocks to expose the blockier surfaces beneath. "This would be like an F8 tornado sweeping across the surface," Schultz said. "These are winds on Mars that will never be seen again unless another impact." The research is published online in the journal Icarus. Schultz says he first saw the streaks during one of his "tours of Mars." In his downtime between projects, he pulls up random images from NASA's orbital spacecraft just to see if he might spot something interesting. In this case, he was looking at infrared images taken during the Martian nighttime by the THEMIS instrument, which flies aboard the Mars Odyssey orbiter. The infrared images capture contrasts in heat retention on the surface. Brighter regions at night indicate surfaces that retain more heat from the previous day than surrounding surfaces, just as grassy fields cool off at night while buildings in the city remain warmer. "You couldn't see these things at all in visible wavelength images, but in the nighttime infrared they're very bright," Schultz said. "Brightness in the infrared indicates blocky surfaces, which retain more heat than surfaces covered by powder and debris. That tells us that something came along and scoured those surfaces bare." And Schultz had an idea what that something might be. He has been studying impacts and impact processes for years using NASA's Vertical Gun Range, a high-powered cannon that can fire projectiles at speeds up to 15,000 miles per hour. "We had been seeing some things in experiments we thought might cause these streaks," he said. When an asteroid or other body strikes a planet at high speed, tons of material from both the impactor and the target surface are instantly vaporized. Schultz's experiments showed that vapor plumes travel outward from an impact point, just above the impact surface, at incredible speeds. Scaling laboratory impacts to the size of those on Mars, a vapor plume's speed would be supersonic. And it would interact with the Martian atmosphere to generate powerful winds. The plume and its associated winds on their own didn't cause the strange streaks, however. The plumes generally travel just above the surface, which prevents the kind of deep scouring seen in the streaked areas. But Schultz and Quintana showed that when the plume strikes a raised surface feature, it disturbs the flow and causes powerful tornadic vortices to form and drop to the surface. And those vortices, the researchers say, are responsible for scouring the narrow streaks. Schultz and Quintana showed that the streaks are nearly always seen in conjunction with raised surface features. Very often, for example, they are associated with the raised ridges of smaller impact craters that were already in place when the larger impact occurred. As the plume raced outward from the larger impact, it encountered the small crater rim, leaving bright twin streaks on the downwind side. "Where these vortices encounter the surface, they sweep away the small particles that sit loose on the surface, exposing the bigger blocky material underneath, and that's what gives us these streaks," Schultz said. Schultz says the streaks could prove useful in establishing rates of erosion and dust deposition in areas where the streaks are found. "We know these formed at the same time as these large craters, and we can date the age of the craters," Schultz said. "So now we have a template for looking at erosion." But with more research, the streaks could eventually reveal much more than that. From a preliminary survey of the planet, the researchers say the streaks appear to form around craters in the ballpark of 20 kilometers across. But they don't appear in all such craters. Why they form in some places and not others could provide information about the Martian surface at the time of the impact. The researchers' experiments reveal that the presence of volatile compounds—a thick layer of water ice on the surface or subsurface, for example—affect the amount the vapor that rushes out from an impact. So in that way, the streaks might serve as indicators of whether ice may have been present at the time of an impact, which could lend insight into reconstructions of past climate on Mars. Equally possible, the streaks could be related to the composition of the impactor, such as rare collisions by high-volatile objects, such as comets. "The next step is to really dig into the conditions that cause the streaks," Schultz said. "They may have a lot to tell us, so stay tuned." Explore further: Sand flow theory could explain water-like streaks on Mars More information: Peter H. Schultz et al, Impact-generated winds on Mars, Icarus (2017). DOI: 10.1016/j.icarus.2017.03.029


News Article | May 12, 2017
Site: news.yahoo.com

If you look at photographs of Martian impact craters and the ejecta around them, you would, on occasion, see craters ringed with mysterious bright streaks that extend outward from the point of impact. What makes these features odd is the fact that they extend much farther from the craters than normal ejecta patterns, and that they are only visible in thermal infrared images. Researchers from Brown University have come up with an explanation for how these streaks formed. In a study published in the latest edition of the journal Icarus, they argue these structures were created by high-speed tornadoes generated by large impacts. According to the authors of the study, who used geological observations made using the THEMIS instrument on board the Mars Odyssey spacecraft , laboratory impact experiments and computer modeling of impact processes, large crater-forming impacts would have created tornado-like wind vortices that reached speeds of up to 500 miles per hour. These tornadoes would then have blasted away dust and small rocks as they swept across the Martian surface. “Where these vortices encounter the surface, they sweep away the small particles that sit loose on the surface, exposing the bigger blocky material underneath, and that’s what gives us these streaks,” Brown University geologist Peter Schultz explained in the statement. “We know these formed at the same time as these large craters, and we can date the age of the craters. So now we have a template for looking at erosion.” The researchers’ experiments showed that after an asteroid or another large body impacts the surface, plumes of vapor travel outward from an impact point, just above the impact surface, at incredible speeds. Although these plumes do not directly gouge out the streaks — since they travel just above the surface — when these swirling winds strike raised surface features, the perturbed flow causes powerful vortices to form and drop to the surface. This phenomenon may be responsible for furrowing out the narrow streaks. “This would be like an F8 tornado sweeping across the surface. These are winds on Mars that will never be seen again unless another impact,” Schultz said. "Brightness in the infrared indicates blocky surfaces, which retain more heat than surfaces covered by powder and debris. That tells us that something came along and scoured those surfaces bare." While this hypothesis does explain how the bright streaks around some of the Martian craters formed, it also raises a few questions. For instance, the researchers found that streaks are only seen around craters that are about 20 kilometers (12.4 miles) wide, and, even more intriguingly, not all craters in this ballpark exhibit such features — something that the researchers can’t yet explain. “The next step is to really dig into the conditions that cause the streaks,” Schultz said. “They may have a lot to tell us.”


News Article | August 30, 2016
Site: www.techtimes.com

Mars, otherwise known as the Red Planet, is a dry and barren place with no clear signs of life. There have been several signs of liquid water on the planet, the latest being a weird and dark streak NASA's Mars Reconnaissance Orbiter came across not too long ago. Should liquid water ever be found on Mars, it would be a huge deal. This is because researchers could locate potential life forms and resources that can be used to make lives better for humanity. However, nothing is ever what it seems at times. As it turns out, researchers are saying, there isn't enough water via those dark streaks as previously hoped. Furthermore, researchers are almost certain that whatever is there, it's not drinkable. To make matters worse, researchers claim the amount of water on Mars cannot exceed that of Earth's driest desert. That's a huge blow to anyone hoping to come across huge swaths of liquid water on the Red Planet's surface. How do scientists come to the conclusion that there isn't much water on the surface of Mars? Well, they used Mars Odyssey's Thermal Emission Imaging System (THEMIS) to monitor the planet's surface from orbit. This is done remotely of course. We understand that whenever water is available between the grain of sand and soil, the temperature on the ground does not heat up as quickly compared to when there's no water available. The deeper the seeps, the more cloistered the ground becomes. Furthermore, after years of analyzing the data from THEMIS, NASA scientists concluded that the soil could only hold just 3 percent of water. That's basically similar levels of dryness found in the driest desert on our planet, the Atacama Desert. "Our findings are consistent with the presence of hydrated salts, because you can have hydrated salt without having enough for the water to start filling pore spaces between particles," said Christopher Edwards, a faculty member in the Department of Physics and Astronomy at Northern Arizona University, in a statement. "Salts can become hydrated by pulling water vapor from the atmosphere, with no need for an underground source of the water." What does this mean? Well, we may have to cease from hoping of ever finding large amounts of water on Mars if these findings turn out to be completely accurate. And with that, it also means we may have to do away with any thought of eve finding life on the planet. Just a little bit of water can be home to life, but the prospects of finding life truly rest on finding large amounts, and this is becoming highly unlikely as time goes by. © 2016 Tech Times, All rights reserved. Do not reproduce without permission.


News Article | November 15, 2016
Site: www.sciencedaily.com

High above the surface, Earth's magnetic field constantly deflects incoming supersonic particles from the sun. These particles are disturbed in regions just outside of Earth's magnetic field -- and some are reflected into a turbulent region called the foreshock. New observations from NASA's THEMIS mission show that this turbulent region can accelerate electrons up to speeds approaching the speed of light. Such extremely fast particles have been observed in near-Earth space and many other places in the universe, but the mechanisms that accelerate them have not yet been concretely understood. The new results provide the first steps towards an answer, while opening up more questions. The research finds electrons can be accelerated to extremely high speeds in a region farther from Earth than previously thought possible -- leading to new inquiries about what causes the acceleration. These findings may change the accepted theories on how electrons can be accelerated not only in shocks near Earth, but also throughout the universe. Having a better understanding of how particles are energized will help scientists and engineers better equip spacecraft and astronauts to deal with these particles, which can cause equipment to malfunction and affect space travelers. "This affects pretty much every field that deals with high-energy particles, from studies of cosmic rays to solar flares and coronal mass ejections, which have the potential to damage satellites and affect astronauts on expeditions to Mars," said Lynn Wilson, lead author of the paper on these results at NASA's Goddard Space Flight Center in Greenbelt, Maryland. The results, published in Physical Review Letters on Nov. 14, 2016, describe how such particles may get accelerated in specific regions just beyond Earth's magnetic field. Typically, a particle streaming toward Earth first encounters a boundary region known as the bow shock, which forms a protective barrier between the sun and Earth. The magnetic field in the bow shock slows the particles, causing most to be deflected away from Earth, though some are reflected back towards the sun. These reflected particles form a region of electrons and ions called the foreshock region. Some of those particles in the foreshock region are highly energetic, fast moving electrons and ions. Historically, scientists have thought one way these particles get to such high energies is by bouncing back and forth across the bow shock, gaining a little extra energy from each collision. However, the new observations suggest the particles can also gain energy through electromagnetic activity in the foreshock region itself. The observations that led to this discovery were taken from one of the THEMIS -- short for Time History of Events and Macroscale Interactions during Substorms -- mission satellites. The five THEMIS satellites circled Earth to study how the planet's magnetosphere captured and released solar wind energy, in order to understand what initiates the geomagnetic substorms that cause aurora. The THEMIS orbits took the spacecraft across the foreshock boundary regions. The primary THEMIS mission concluded successfully in 2010 and now two of the satellites collect data in orbit around the moon. Operating between the sun and Earth, the spacecraft found electrons accelerated to extremely high energies. The accelerated observations lasted less than a minute, but were much higher than the average energy of particles in the region, and much higher than can be explained by collisions alone. Simultaneous observations from the Wind and STEREO spacecraft showed no solar radio bursts or interplanetary shocks, so the high-energy electrons did not originate from solar activity. "This is a puzzling case because we're seeing energetic electrons where we don't think they should be, and no model fits them," said David Sibeck, co-author and THEMIS project scientist at NASA Goddard. "There is a gap in our knowledge, something basic is missing." The electrons also could not have originated from the bow shock, as had been previously thought. If the electrons were accelerated in the bow shock, they would have a preferred movement direction and location -- in line with the magnetic field and moving away from the bow shock in a small, specific region. However, the observed electrons were moving in all directions, not just along magnetic field lines. Additionally, the bow shock can only produce energies at roughly one tenth of the observed electrons' energies. Instead, the cause of the electrons' acceleration was found to be within the foreshock region itself. "It seems to suggest that incredibly small scale things are doing this because the large scale stuff can't explain it," Wilson said. High-energy particles have been observed in the foreshock region for more than 50 years, but until now, no one had seen the high-energy electrons originate from within the foreshock region. This is partially due to the short timescale on which the electrons are accelerated, as previous observations had averaged over several minutes, which may have hidden any event. THEMIS gathers observations much more quickly, making it uniquely able to see the particles. Next, the researchers intend to gather more observations from THEMIS to determine the specific mechanism behind the electrons' acceleration.

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