The second-largest mass extinction in Earth's history coincided with a short but intense ice age during which enormous glaciers grew and sea levels dropped. Although it has long been agreed that the so-called Late Ordovician mass extinction -- which occurred about 450 million years ago -- was related to climate change, exactly how the climate change produced the extinction has not been known. Now, a team led by scientists at the California Institute of Technology (Caltech) has created a framework for weighing the factors that might have led to mass extinction and has used that framework to determine that the majority of extinctions were caused by habitat loss due to falling sea levels and cooling of the tropical oceans.
The work -- performed by scientists at Caltech and the University of Wisconsin, Madison -- is described in a paper currently online in the early edition of the Proceedings of the National Academy of Sciences.
The researchers combined information from two separate databases to overlay fossil occurrences on the sedimentary rock record of North America around the time of the extinction, an event that wiped out about 75 percent of marine species alive then. At that time, North America was an island continent geologists call Laurentia, located in the tropics.
Comparing the groups of species, or genera, that went extinct during the event with those that survived, the researchers were able to figure out the relative importance of several variables in dictating whether a genus went extinct during a 50-million-year interval around the mass extinction.
"What we did was essentially the same thing you'd do if confronted with a disease epidemic," says Seth Finnegan, postdoctoral scholar at Caltech and lead author of the study. "You ask who is affected and who is unaffected, and that can tell you a lot about what's causing the epidemic."
As it turns out, the strongest predictive factors of extinction on Laurentia were both the percentage of a genus's habitat that was lost when the sea level dropped and a genus's ability to tolerate broader ranges of temperatures. Groups that lost large portions of their habitat as ice sheets grew and sea levels fell, and those that had always been confined to warm tropical waters, were most likely to go extinct as a result of the rapid climate change.
"This is the first really attractive demonstration of how you can use multivariate approaches to try to understand extinctions, which reflect amazingly complex suites of processes," says Woodward Fischer, an assistant professor of geobiology at Caltech and principal investigator on the study. "As earth scientists, we love to debate different environmental and ecological factors in extinctions, but the truth is that all of these factors interact with one another in complicated ways, and you need a way of teasing these interactions apart. I'm sure this framework will be profitably applied to extinction events in other geologic intervals."
The analysis enabled the researchers to largely rule out a hypothesis, known as the record-bias hypothesis, which says that the extinction might be explained by a significant gap in the fossil record, also related to glaciation. After all, if sea levels fell and continents were no longer flooded, sedimentary rocks with fossils would not accumulate. Therefore, the last record of any species that went extinct during the gap would show up immediately before the gap, creating the appearance of a mass extinction.
Finnegan reasoned that this record-bias hypothesis would predict that the duration of a gap in the record should correlate with higher numbers of extinctions -- if a gap persisted longer, more groups should have gone extinct during that time, so it should appear that more species went extinct all at once than for shorter gaps. But in the case of the Late Ordovician, the researchers found that the duration of the gap did not matter, indicating that a mass extinction very likely did occur.
"We have found that the Late Ordovician mass extinction most likely represents a real pulse of extinction -- that many living things genuinely went extinct then," says Finnegan. "It's not that the record went bad and we just don't recover them after that."
Monday, April 16, 2012
Monday, April 9, 2012
Copper Chains: Earth's Deep-Seated Hold On Copper Revealed
Earth is clingy when it comes to copper. A new Rice University study recently published in the journal Science finds that nature conspires at scales both large and small -- from the realms of tectonic plates down to molecular bonds -- to keep most of Earth's copper buried dozens of miles below ground.
"Everything throughout history shows us that Earth does not want to give up its copper to the continental crust," said Rice geochemist Cin-Ty Lee, the lead author of the study. "Both the building blocks for continents and the continental crust itself, dating back as much as 3 billion years, are highly depleted in copper."
Finding copper is more than an academic exercise. With global demand for electronics growing rapidly, some studies have estimated the world's demand for copper could exceed supply in as little as six years. The new study could help, because it suggests where undiscovered caches of copper might lie.
But the copper clues were just a happy accident.
"We didn't go into this looking for copper," Lee said. "We were originally interested in how continents form and more specifically in the oxidation state of volcanoes."
Earth scientists have long debated whether an oxygen-rich atmosphere might be required for continent formation. The idea stems from the fact that Earth may not have had many continents for at least the first billion years of its existence and that Earth's continents may have begun forming around the time that oxygen became a significant component of the atmosphere.
In their search for answers, Lee and colleagues set out to examine Earth's arc magmas -- the molten building blocks for continents. Arc magmas get their start deep in the planet in areas called subduction zones, where one of Earth's tectonic plates slides beneath another. When plates subduct, two things happen. First, they bring oxidized crust and sediments from Earth's surface into the mantle. Second, the subducting plate drives a return flow of hot mantle upwards from Earth's deep interior. During this return flow, the hot mantle not only melts itself but may also cause melting of the recycled sediments. Arc magmas are thought to form under these conditions, so if oxygen were required for continental crust formation, it would mostly likely come from these recycled segments.
"If oxidized materials are necessary for generating such melts, we should see evidence of it all the way from where the arc magmas form to the point where the new continent-building material is released from arc volcanoes," Lee said.
Lee and colleagues examined xenoliths, rocks that formed deep inside Earth and were carried up to the surface in volcanic eruptions. Specifically, they studied garnet pyroxenite xenoliths thought to represent the first crystallized products of arc magmas from the deep roots of an arc some 50 kilometers below Earth's surface. Rather than finding evidence of oxidation, they found sulfides -- minerals that contain reduced forms of sulfur bonded to metals like copper, nickel and iron. If conditions were highly oxidizing, Lee said, these sulfide minerals would be destabilized and allow these elements, particularly copper, to bond with oxygen.
Because sulfides are also heavy and dense, they tend to sink and get left behind in the deep parts of arc systems, like a blob of dense material that stays at the bottom of a lava lamp while less dense material rises to the top.
"This explains why copper deposits, in general, are so rare," Lee said. "The Earth wants to hold it deep and not give it up."
Lee said deciding where to look for undiscovered copper deposits requires an understanding of the conditions needed to overcome the forces that conspire to keep it deep inside the planet.
"As a continental arc matures, the copper-rich sulfides are trapped deep and accumulate," he said. "But if the continental arc grows thicker over time, the accumulated copper-bearing sulfides are driven to deeper depths where the higher temperatures can re-melt these copper-rich dregs, releasing them to rejoin arc magmas."
These conditions were met in the Andes Mountains and in western North America. He said other potential sources of undiscovered copper include Siberia, northern China, Mongolia and parts of Australia.
Lee noted that a high school intern played a role in the research paper. Daphne Jin, now a freshman at the University of Chicago, made her contribution to the research as a high school intern from Clements High School in the Houston suburb of Sugarland.
"The paper really wouldn't have been as broad without Daphne's contribution," Lee said. "I originally struggled with an assignment for her because I didn't and still don't have large projects where a student can just fit in. I try to make sure every student has a chance to do something new, but often I just run out of ideas."
Lee eventually asked Jin to compile information from published studies about the average concentration of all the first-row of transition elements in the periodic table in various samples of continental crust and mantle collected the world over.
"She came back and showed me the results, and we could see that the average continental crust itself, which has been built over 3 billion years of Earth's history in Africa, Siberia, North America, South America, etc., was all depleted in copper," Lee said. "Up to that point we'd been looking at the building blocks of continents, but this showed us that the continents themselves followed the same pattern. It was all internally consistent."
In addition to Jin, Lee's co-authors on the report include Rajdeep Dasgupta, assistant professor of Earth science at Rice; Rice postdoctoral researchers Peter Luffi and Veronique Roux; Rice graduate student Emily Chin; visiting graduate student Romain Bouchet of the École Normale Supérieure in Lyon, France; Douglas Morton, professor of geology at the University of California, Riverside; and Qing-zhu Yin, professor of geology at the University of California, Davis.
"Everything throughout history shows us that Earth does not want to give up its copper to the continental crust," said Rice geochemist Cin-Ty Lee, the lead author of the study. "Both the building blocks for continents and the continental crust itself, dating back as much as 3 billion years, are highly depleted in copper."
Finding copper is more than an academic exercise. With global demand for electronics growing rapidly, some studies have estimated the world's demand for copper could exceed supply in as little as six years. The new study could help, because it suggests where undiscovered caches of copper might lie.
But the copper clues were just a happy accident.
"We didn't go into this looking for copper," Lee said. "We were originally interested in how continents form and more specifically in the oxidation state of volcanoes."
Earth scientists have long debated whether an oxygen-rich atmosphere might be required for continent formation. The idea stems from the fact that Earth may not have had many continents for at least the first billion years of its existence and that Earth's continents may have begun forming around the time that oxygen became a significant component of the atmosphere.
In their search for answers, Lee and colleagues set out to examine Earth's arc magmas -- the molten building blocks for continents. Arc magmas get their start deep in the planet in areas called subduction zones, where one of Earth's tectonic plates slides beneath another. When plates subduct, two things happen. First, they bring oxidized crust and sediments from Earth's surface into the mantle. Second, the subducting plate drives a return flow of hot mantle upwards from Earth's deep interior. During this return flow, the hot mantle not only melts itself but may also cause melting of the recycled sediments. Arc magmas are thought to form under these conditions, so if oxygen were required for continental crust formation, it would mostly likely come from these recycled segments.
"If oxidized materials are necessary for generating such melts, we should see evidence of it all the way from where the arc magmas form to the point where the new continent-building material is released from arc volcanoes," Lee said.
Lee and colleagues examined xenoliths, rocks that formed deep inside Earth and were carried up to the surface in volcanic eruptions. Specifically, they studied garnet pyroxenite xenoliths thought to represent the first crystallized products of arc magmas from the deep roots of an arc some 50 kilometers below Earth's surface. Rather than finding evidence of oxidation, they found sulfides -- minerals that contain reduced forms of sulfur bonded to metals like copper, nickel and iron. If conditions were highly oxidizing, Lee said, these sulfide minerals would be destabilized and allow these elements, particularly copper, to bond with oxygen.
Because sulfides are also heavy and dense, they tend to sink and get left behind in the deep parts of arc systems, like a blob of dense material that stays at the bottom of a lava lamp while less dense material rises to the top.
"This explains why copper deposits, in general, are so rare," Lee said. "The Earth wants to hold it deep and not give it up."
Lee said deciding where to look for undiscovered copper deposits requires an understanding of the conditions needed to overcome the forces that conspire to keep it deep inside the planet.
"As a continental arc matures, the copper-rich sulfides are trapped deep and accumulate," he said. "But if the continental arc grows thicker over time, the accumulated copper-bearing sulfides are driven to deeper depths where the higher temperatures can re-melt these copper-rich dregs, releasing them to rejoin arc magmas."
These conditions were met in the Andes Mountains and in western North America. He said other potential sources of undiscovered copper include Siberia, northern China, Mongolia and parts of Australia.
Lee noted that a high school intern played a role in the research paper. Daphne Jin, now a freshman at the University of Chicago, made her contribution to the research as a high school intern from Clements High School in the Houston suburb of Sugarland.
"The paper really wouldn't have been as broad without Daphne's contribution," Lee said. "I originally struggled with an assignment for her because I didn't and still don't have large projects where a student can just fit in. I try to make sure every student has a chance to do something new, but often I just run out of ideas."
Lee eventually asked Jin to compile information from published studies about the average concentration of all the first-row of transition elements in the periodic table in various samples of continental crust and mantle collected the world over.
"She came back and showed me the results, and we could see that the average continental crust itself, which has been built over 3 billion years of Earth's history in Africa, Siberia, North America, South America, etc., was all depleted in copper," Lee said. "Up to that point we'd been looking at the building blocks of continents, but this showed us that the continents themselves followed the same pattern. It was all internally consistent."
In addition to Jin, Lee's co-authors on the report include Rajdeep Dasgupta, assistant professor of Earth science at Rice; Rice postdoctoral researchers Peter Luffi and Veronique Roux; Rice graduate student Emily Chin; visiting graduate student Romain Bouchet of the École Normale Supérieure in Lyon, France; Douglas Morton, professor of geology at the University of California, Riverside; and Qing-zhu Yin, professor of geology at the University of California, Davis.
Coral Links Ice Sheet Collapse to Ancient 'Mega Flood'
Coral off Tahiti has linked the collapse of massive ice sheets 14,600 years ago to a dramatic and rapid rise in global sea-levels of around 14 metres.
Previous research could not accurately date the sea-level rise but now an Aix-Marseille University-led team, including Oxford University scientists Alex Thomas and Gideon Henderson, has confirmed that the event occurred 14,650-14,310 years ago at the same time as a period of rapid climate change known as the Bølling warming.
The finding will help scientists currently modelling future climate change scenarios to factor in the dynamic behaviour of major ice sheets.
A report of the research is published in this week's Nature.
'It is vital that we look into Earth's geological past to understand rare but high impact events, such as the collapse of giant ice sheets that occurred 14,600 years ago,' said Dr Alex Thomas of Oxford University's Department of Earth Sciences, an author of the paper. 'Our work gives a window onto an extreme event in which deglaciation coincided with a dramatic and rapid rise in global sea levels -- an ancient 'mega flood'. Sea level rose more than ten times more quickly than it is rising now! This is an excellent test bed for climate models: if they can reproduce this extraordinary event, it will improve confidence that they can also predict future change accurately.'
During the Bølling warming high latitudes of the Northern hemisphere warmed as much as 15 degrees Celsius in a few tens of decades. The team has used dating evidence from Tahitian corals to constrain the sea level rise to within a period of 350 years, although the actual rise may well have occurred much more quickly and would have been distributed unevenly around the world's shorelines.
Dr Thomas said: 'The Tahitian coral is important because samples, thousands of years old, can be dated to within plus or minus 30 years. Because Tahiti is an ocean island, far away from major ice sheets, sea-level evidence from its coral reefs gives us close to the 'magic' average of sea levels across the globe, it is also subsiding into the ocean at a steady pace that we can easily adjust for.'
The research is part of a large international consortium, the Integrated Ocean Drilling Program (IODP), and the coral samples were obtained by drilling down to the sea floor from a ship positioned off the coast of Tahiti.
What exactly caused the Bølling warming is a matter of intense debate: a leading theory is that the ocean's circulation changed so that more heat was transported into Northern latitudes.
The new sea-level evidence suggests that a considerable portion of the water causing the sea-level rise at this time must have come from melting of the ice sheets in Antarctica, which sent a 'pulse' of freshwater around the globe. However, whether the freshwater pulse helped to warm the climate or was a result of an already warming world remains unclear.
Previous research could not accurately date the sea-level rise but now an Aix-Marseille University-led team, including Oxford University scientists Alex Thomas and Gideon Henderson, has confirmed that the event occurred 14,650-14,310 years ago at the same time as a period of rapid climate change known as the Bølling warming.
The finding will help scientists currently modelling future climate change scenarios to factor in the dynamic behaviour of major ice sheets.
A report of the research is published in this week's Nature.
'It is vital that we look into Earth's geological past to understand rare but high impact events, such as the collapse of giant ice sheets that occurred 14,600 years ago,' said Dr Alex Thomas of Oxford University's Department of Earth Sciences, an author of the paper. 'Our work gives a window onto an extreme event in which deglaciation coincided with a dramatic and rapid rise in global sea levels -- an ancient 'mega flood'. Sea level rose more than ten times more quickly than it is rising now! This is an excellent test bed for climate models: if they can reproduce this extraordinary event, it will improve confidence that they can also predict future change accurately.'
During the Bølling warming high latitudes of the Northern hemisphere warmed as much as 15 degrees Celsius in a few tens of decades. The team has used dating evidence from Tahitian corals to constrain the sea level rise to within a period of 350 years, although the actual rise may well have occurred much more quickly and would have been distributed unevenly around the world's shorelines.
Dr Thomas said: 'The Tahitian coral is important because samples, thousands of years old, can be dated to within plus or minus 30 years. Because Tahiti is an ocean island, far away from major ice sheets, sea-level evidence from its coral reefs gives us close to the 'magic' average of sea levels across the globe, it is also subsiding into the ocean at a steady pace that we can easily adjust for.'
The research is part of a large international consortium, the Integrated Ocean Drilling Program (IODP), and the coral samples were obtained by drilling down to the sea floor from a ship positioned off the coast of Tahiti.
What exactly caused the Bølling warming is a matter of intense debate: a leading theory is that the ocean's circulation changed so that more heat was transported into Northern latitudes.
The new sea-level evidence suggests that a considerable portion of the water causing the sea-level rise at this time must have come from melting of the ice sheets in Antarctica, which sent a 'pulse' of freshwater around the globe. However, whether the freshwater pulse helped to warm the climate or was a result of an already warming world remains unclear.
Thursday, October 7, 2010
Oldest Evidence of Dinosaurs in Footprints
Oldest Evidence of Dinosaurs in Footprints: Dinosaur Lineage Emerged
Soon After Massive Permian Extinction
The oldest evidence of the dinosaur lineage -- fossilized tracks -- is described in Proceedings of the Royal Society B. Just one or two million years after the massive Permian-Triassic extinction, an animal smaller than a house cat walked across fine mud in what is now Poland.
This fossilized trackway places the very closest relatives of dinosaurs on Earth about 250 million years ago -- 5 to 9 million years earlier than previously described fossilized skeletal material has indicated. The paper also described the 246-million-year-old Sphingopus footprints, the oldest evidence of a bipedal and large-bodied dinosaur.
"We see the closest dinosaur cousins immediately after the worst mass extinction," says Stephen Brusatte, a graduate student affiliated with the Division of Paleontology at the American Museum of Natural History. "The biggest crisis in the history of life also created one of the greatest opportunities in the history of life by emptying the landscape and making it possible for dinosaurs to evolve."
The new paper analyzes three sets of footprints from three different sites in the Holy Cross Mountains of central Poland. The sites, all quarries within a 25-mile radius of each other, are windows into three ecosystems because they represent different times periods. The Stryczowice trackway is the oldest at 250 million years. The Baranów trackway is the most recent at 246 million years of age while the Wióry trackway is sandwiched in time between the others.
Because footprints are only an imprint of a small part of the skeleton, identification of trackmakers is often tricky. Luckily, dinosaurs have a very distinctive gait, especially when compared to their diapsid relatives (the evolutionary group that includes birds, reptiles, and extinct lineages) like crocodiles and lizards. While lizards and crocodiles have a splayed walking style, dinosaurs place their two feet closer together. The footprints at all three Polish sites show this feature as well as indisputable dinosaur-like features, including three prominent central toes and reduced outer two toes, a parallel alignment of these three digits (a bunched foot), and a straight back edge of footprints, additional evidence of a dinosaur-like simple hinged ankle.
Because all of these features are seen in footprints at the oldest site, Brusatte and colleagues conclude that the Stryczowice prints -- which are only a few centimeters in length -- are the oldest evidence of the dinosaur lineage. These dinosaurs, though, are considered "stem dinosaurs," or the immediate relatives of dinosaurs not part of the slightly more derived clade that technically defines dinosaurs. Also, this animal did walk on all four limbs, an abnormal posture for early dinosaurs and their close relatives, although it appears that its forelimbs were already being reduced to more dinosaur-like proportions since the footprints overstep handprints.
The Baranów and Wióry trackways show changes early in the evolutionary history of dinosaurs. Wióry at 248-249 million years ago shows slight diversification in the types of tracks, but all tracks remain quadrupedal. Footprints from Baranów at 246 million years ago, however, may be the earliest evidence of moderately large-bodied and bipedal true dinosaurs. These tracks, which are called Sphingopus, are 15 centimeters long.
"Poland is a new frontier for understanding the earliest evolution of dinosaurs," says Grzegorz Niedźwiedzki of the University of Warsaw and the Polish Academy of Sciences, who led the project and has been excavating footprints from the three sites for nearly a decade. "It used to be that most of the important fossils were from Argentina or the southwestern U.S., but in Poland we have several sites that yield footprints and bones from the oldest dinosaurs and their closest cousins, stretching throughout the entire Triassic Period."
Finally, although the dinosaur group emerged soon after the Permian extinction, dinosaur-like tracks are rare in the footprint assemblages, representing only 2-3 percent of the prints discovered as opposed to 40-50 percent for crocodile-like archosaurs. Dinosaurs became more abundant tens of millions of years later.
"For the first 20-50 million years of dinosaur history, dinosaurs and their closest relatives were living in the shadow of their much more diverse, successful, and abundant crocodile-like cousins," says Brusatte. "The oldest dinosaurs were small and rare."
In addition to Brusatte and Niedźwiedzki, Richard Butler of the Bayerische Staatssammlung für Paläontologie und Geologie in Germany was an author of the paper. Brusatte is also affiliated with Columbia University. The research was funded in part by the National Science Foundation, the Percy Sladen Fund, the Alexander von Humboldt Research Fellowship, and the University of Warsaw.
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by American Museum of Natural History, via EurekAlert!, a service of AAAS.
Journal Reference:
Stephen L. Brusatte, Grzegorz Niedźwiedzki, Richard J. Butler. Footprints pull origin and diversification of dinosaur stem lineage deep into Early Triassic. Proceedings of the Royal Society B, 2010; DOI: 10.1098/rspb.2010.1746
The oldest evidence of the dinosaur lineage -- fossilized tracks -- is described in Proceedings of the Royal Society B. Just one or two million years after the massive Permian-Triassic extinction, an animal smaller than a house cat walked across fine mud in what is now Poland.
This fossilized trackway places the very closest relatives of dinosaurs on Earth about 250 million years ago -- 5 to 9 million years earlier than previously described fossilized skeletal material has indicated. The paper also described the 246-million-year-old Sphingopus footprints, the oldest evidence of a bipedal and large-bodied dinosaur.
"We see the closest dinosaur cousins immediately after the worst mass extinction," says Stephen Brusatte, a graduate student affiliated with the Division of Paleontology at the American Museum of Natural History. "The biggest crisis in the history of life also created one of the greatest opportunities in the history of life by emptying the landscape and making it possible for dinosaurs to evolve."
The new paper analyzes three sets of footprints from three different sites in the Holy Cross Mountains of central Poland. The sites, all quarries within a 25-mile radius of each other, are windows into three ecosystems because they represent different times periods. The Stryczowice trackway is the oldest at 250 million years. The Baranów trackway is the most recent at 246 million years of age while the Wióry trackway is sandwiched in time between the others.
Because footprints are only an imprint of a small part of the skeleton, identification of trackmakers is often tricky. Luckily, dinosaurs have a very distinctive gait, especially when compared to their diapsid relatives (the evolutionary group that includes birds, reptiles, and extinct lineages) like crocodiles and lizards. While lizards and crocodiles have a splayed walking style, dinosaurs place their two feet closer together. The footprints at all three Polish sites show this feature as well as indisputable dinosaur-like features, including three prominent central toes and reduced outer two toes, a parallel alignment of these three digits (a bunched foot), and a straight back edge of footprints, additional evidence of a dinosaur-like simple hinged ankle.
Because all of these features are seen in footprints at the oldest site, Brusatte and colleagues conclude that the Stryczowice prints -- which are only a few centimeters in length -- are the oldest evidence of the dinosaur lineage. These dinosaurs, though, are considered "stem dinosaurs," or the immediate relatives of dinosaurs not part of the slightly more derived clade that technically defines dinosaurs. Also, this animal did walk on all four limbs, an abnormal posture for early dinosaurs and their close relatives, although it appears that its forelimbs were already being reduced to more dinosaur-like proportions since the footprints overstep handprints.
The Baranów and Wióry trackways show changes early in the evolutionary history of dinosaurs. Wióry at 248-249 million years ago shows slight diversification in the types of tracks, but all tracks remain quadrupedal. Footprints from Baranów at 246 million years ago, however, may be the earliest evidence of moderately large-bodied and bipedal true dinosaurs. These tracks, which are called Sphingopus, are 15 centimeters long.
"Poland is a new frontier for understanding the earliest evolution of dinosaurs," says Grzegorz Niedźwiedzki of the University of Warsaw and the Polish Academy of Sciences, who led the project and has been excavating footprints from the three sites for nearly a decade. "It used to be that most of the important fossils were from Argentina or the southwestern U.S., but in Poland we have several sites that yield footprints and bones from the oldest dinosaurs and their closest cousins, stretching throughout the entire Triassic Period."
Finally, although the dinosaur group emerged soon after the Permian extinction, dinosaur-like tracks are rare in the footprint assemblages, representing only 2-3 percent of the prints discovered as opposed to 40-50 percent for crocodile-like archosaurs. Dinosaurs became more abundant tens of millions of years later.
"For the first 20-50 million years of dinosaur history, dinosaurs and their closest relatives were living in the shadow of their much more diverse, successful, and abundant crocodile-like cousins," says Brusatte. "The oldest dinosaurs were small and rare."
In addition to Brusatte and Niedźwiedzki, Richard Butler of the Bayerische Staatssammlung für Paläontologie und Geologie in Germany was an author of the paper. Brusatte is also affiliated with Columbia University. The research was funded in part by the National Science Foundation, the Percy Sladen Fund, the Alexander von Humboldt Research Fellowship, and the University of Warsaw.
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by American Museum of Natural History, via EurekAlert!, a service of AAAS.
Journal Reference:
Stephen L. Brusatte, Grzegorz Niedźwiedzki, Richard J. Butler. Footprints pull origin and diversification of dinosaur stem lineage deep into Early Triassic. Proceedings of the Royal Society B, 2010; DOI: 10.1098/rspb.2010.1746
New Fossil Suggests Dinosaurs Not So Fierce After All
A new species of dinosaur discovered in Arizona suggests dinosaurs did not spread throughout the world by overpowering other species, but by taking advantage of a natural catastrophe that wiped out their competitors.
Tim Rowe, professor of paleontology at The University of Texas at Austin's Jackson School of Geosciences, led the effort to describe the new dinosaur along with co-authors Hans-Dieter Sues, curator of vertebrate paleontology at the National Museum of Natural History in Washington, DC and Robert R. Reisz, professor and chair of biology at the University of Toronto. The description appears in the online edition of the journal Proceedings of the Royal Society B on Oct. 6.
Sarahsaurus, which lived about 190 million years ago during the Early Jurassic Period, was 14 feet long and weighed about 250 pounds. Sarahsaurus was a sauropodomorph, a small but closely related ancestor to sauropods, the largest land animals in history.
Conventional wisdom says that soon after dinosaurs originated in what is now South America, they rapidly spread out to conquer every corner of the world, so smart and powerful they overwhelmed all the animals in their path. Sarahsaurus challenges that view.
One of the five great mass extinction events in Earth's history happened at the end of the Triassic Period 200 million years ago, wiping out many of the potential competitors to dinosaurs. Evidence from Sarahsaurus and two other early sauropodomorphs suggests that each migrated into North America in separate waves long after the extinction and that no such dinosaurs migrated there before the extinction.
"We used to think of dinosaurs as fierce creatures that outcompeted everyone else," said Rowe. "Now we're starting to see that's not really the case. They were humbler, more opportunistic creatures. They didn't invade the neighborhood. They waited for the residents to leave and when no one was watching, they moved in."
Sarahsaurus had physical traits usually associated with gigantic animals. For example, its thigh bones were long and straight like pillars, yet were not much larger than a human's thigh bones. Sarahsaurus shows that sauropodmorphs started out small and later evolved to a very large size.
"And so it's starting to look like some of our ideas about how size and evolution work are probably in need of revision," said Rowe, "and that some of the features we thought were tied to gigantism and the physics and mechanics of the bones may not be right."
Rowe is also intrigued by the new dinosaur's hands.
"We've never found anything like this in western North America," he said. "Its hand is smaller than my hand, but if you line the base of the thumbs up, this small hand is much more powerfully built than my hand and it has these big claws. It's a very strange animal. It's doing something with its hands that involved great strength and power, but we don't know what."
Sarahsaurus is named in honor of Sarah (Mrs. Ernest) Butler, an Austin philanthropist and long time supporter of the arts and sciences. Butler chaired a fundraising committee for the Dino Pit, an interactive exhibit Rowe helped create at the Austin Nature and Science Center that encourages children to dig up their own fossil replicas. The Dino Pit had been talked about for 20 years, but fundraising efforts stalled until Butler became chair.
"I told her if she really raised a million dollars to build the Dino Pit, I'd name a dinosaur after her," he said.
A team of researchers and students led by Rowe discovered Sarahsaurus on a field trip in Arizona in 1997. To reach publication, the team had to obtain excavation permits, excavate the site over three years, remove each fossil fragment from surrounding rock, measure and analyze each piece, and CT scan pieces to study internal structures.
"It took me 13 years, but I'm delighted by the great success of the Dino Pit, which hundreds of thousands of kids have now visited. And also that we had the luck to make a find of suitable importance to carry Sarah's name."
This research was funded in part by an Assembling the Tree of Life grant from the National Science Foundation (NSF AToL 0531767).
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Texas at Austin.
Journal Reference:
Timothy B. Rowe, Hans-Dieter Sues, Robert R. Reisz. Dispersal and diversity in the earliest North American sauropodomorph dinosaurs, with a description of a new taxon. Proceedings of the Royal Society B, DOI: 10.1098/rspb.2010.1867
Thursday, September 2, 2010
Astronomers Find Potassium in Giant Planet's Atmosphere
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This is a view of the Gran Telescopio Canarias in Spain's Canary Islands. With its 10.4-meter diameter mirror, the telescope has more light-collecting area than any other. It was used by University of Florida astronomers to analyze light passing through the upper atmosphere of the giant planet HD 80606 b, about 190 light years from Earth, and determine that its atmosphere contains the element potassium. (Credit: Photo by Miguel Briganti/SMM/IAC)
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Any driver who's seen deer silhouetted by the headlights of an oncoming car knows that vital information can be conveyed by the outlines of objects.
Building on this concept, University of Florida astronomers have analyzed light passing through the upper atmosphere of the giant planet HD 80606 b, about 190 light years from Earth, and determined that its atmosphere contains the element potassium.
"It's wonderful that this method works so well for Jupiter-sized planets," said Knicole Colón, a UF astronomy doctoral student. "Now, we're working to apply this technique to observe smaller planets in an effort to pinpoint the components of their atmospheres."
Coincidentally, another team led by David Sing at the University of Exeter, in Devon, U.K., has just used the same technique to detect potassium in the atmosphere of XO-2b, another huge planet about 485 light years from Earth.
Both planets, known as gas giants, have extremely high temperatures by earthly standards -- HD 80606 b reaches about 2,200 degrees Fahrenheit and XO-2b is about 1,700 degrees. That's hot enough to vaporize potassium.
Together, these observations support previous computer models that predicted what the atmospheres of such planets would be like. The findings also demonstrate the value of a new observational technique that could one day aid in the characterization of planets that might support life. The two groups' findings are available online at the arXiv preprint server, http://arxiv.org, and have been submitted to the journals Astronomy & Astrophysics and the Monthly Notices of the Royal Astronomical Society. Colón and Sing will present their findings at the ExoClimes 2010 conference to be held at the University of Exeter, Sept. 7-10.
The observational technique is called narrow-band transit spectrophotometry, and it can measure the light absorbed by the atoms and molecules in a planet's atmosphere, said Eric Ford, a UF astronomy associate professor and Colón's adviser.
"This new technique only works for planets that pass in front of their parent stars as viewed from Earth. Most of the nearly 500 known planets do not, and even fewer orbit stars that are bright enough for such precise observations," Ford said. "Another challenge is that observations must be carefully timed, in order to see the planets in silhouette against the backlighting of their parent star."
Transit spectrophotometry works like this: While the planet is backlit, astronomers measure the light that passed through its atmosphere. Atoms and molecules absorb specific wavelengths (colors) of light, providing a chemical signature that scientists can recognize. By analyzing the amount of absorption by the planet's atmosphere at specific wavelengths, astronomers can detect the presence of a particular atom or molecule -- in this case, potassium.
The UF team -- Colón and Ford, along with colleagues from the University of California, Santa Cruz, Penn State University, Wesleyan University and the Universidad de La Laguna in Tenerife, Spain -- had help from another technological breakthrough.
These researchers, as well as the Exeter team, used one of the world's most powerful telescopes, the Gran Telescopio Canarias. The observatory includes a mirror almost 35 feet wide and is situated at one of the world's best locations for star-gazing, in the Canary Islands off the northwest coast of Africa. UF is a 5 percent partner in the enormous telescope, that captures enough light to make transit spectrophotometry possible, Colón said.
Sing says he's excited about future prospects for transit spectrophotometry.
"The initial results from both teams have been very encouraging," Sing said. "We still haven't explored the full capabilities or ultimate limitations of the instrument yet."
In 2002, the Hubble Space Telescope detected a similar element, sodium, in the atmosphere of the gas giant planet HD 209458 b. Since then, astronomers have detected sodium in only one other planet. Colón plans to search for potassium in the atmospheres of additional giant planets to learn about the diversity of planetary atmospheres. She hopes that planet searches such as NASA's Kepler Mission will identify many more planets that cross the faces of their parent stars.
"The Kepler Mission has the precision to find even more planets, including some as small as the Earth," she said. Ultimately, Ford and Colón want to examine smaller, Earth-like planets for molecules such as methane gas and water vapor, as both are intimately linked to life on Earth.
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Florida.
Monday, August 30, 2010
30 thousand displaced by new eruption in Sumatra
This morning a column of smoke and ash 2 thousand meters high. Further 8 000 people transferred from the slopes of Mount Sinabung. A man dies from breathing problems caused by airborne ash. Lava flow expected. Indonesia has over 500 active volcanoes.
The volcano was dormant for 400 years, but for the past two days it has continued to emit smoke and ash and many expect possible lava floods. This morning, the eruption occurred at 6.30 (local time), creating a massive column of smoke 2,000 feet high at least. At least 31 villages six kilometers from the mouth of the crater were evacuated. Mount Sinabung is located in North Sumatra province, 1300 km northwest of Jakarta.
The National Civil Protection is advising residents and displaced people to wear masks. In fact a man died from breathing problems because of the ashes scattered in the atmosphere.
Volcanologists have had to admit little knowledge of the characteristics of Sinabung Mountain, since it’s remained dormant for a long time.
Indonesia is considered the area with the highest number of active volcanoes in the world: at least 500, of which 68 are the most dangerous because they are situated in populated areas like Java and Sumatra.
New View of Tectonic Plates
New View of Tectonic Plates: Computer Modeling of Earth's Mantle
Flow, Plate Motions, and Fault Zones
Computational scientists and geophysicists at the University of Texas at Austin and the California Institute of Technology (Caltech) have developed new computer algorithms that for the first time allow for the simultaneous modeling of Earth's mantle flow, large-scale tectonic plate motions, and the behavior of individual fault zones, to produce an unprecedented view of plate tectonics and the forces that drive it.
A paper describing the whole-earth model and its underlying algorithms will be published in the August 27 issue of the journal Science and also featured on the cover.
The work "illustrates the interplay between making important advances in science and pushing the envelope of computational science," says Michael Gurnis, the John E. and Hazel S. Smits Professor of Geophysics, director of the Caltech Seismological Laboratory, and a coauthor of the Science paper.
To create the new model, computational scientists at Texas's Institute for Computational Engineering and Sciences (ICES) -- a team that included Omar Ghattas, the John A. and Katherine G. Jackson Chair in Computational Geosciences and professor of geological sciences and mechanical engineering, and research associates Georg Stadler and Carsten Burstedde -- pushed the envelope of a computational technique known as Adaptive Mesh Refinement (AMR).
Partial differential equations such as those describing mantle flow are solved by subdividing the region of interest (such as the mantle) into a computational grid. Ordinarily, the resolution is kept the same throughout the grid. However, many problems feature small-scale dynamics that are found only in limited regions. "AMR methods adaptively create finer resolution only where it's needed," explains Ghattas. "This leads to huge reductions in the number of grid points, making possible simulations that were previously out of reach."
"The complexity of managing adaptivity among thousands of processors, however, has meant that current AMR algorithms have not scaled well on modern petascale supercomputers," he adds. Petascale computers are capable of one million billion operations per second. To overcome this long-standing problem, the group developed new algorithms that, Burstedde says, "allows for adaptivity in a way that scales to the hundreds of thousands of processor cores of the largest supercomputers available today."
With the new algorithms, the scientists were able to simulate global mantle flow and how it manifests as plate tectonics and the motion of individual faults. According to Stadler, the AMR algorithms reduced the size of the simulations by a factor of 5,000, permitting them to fit on fewer than 10,000 processors and run overnight on the Ranger supercomputer at the National Science Foundation (NSF)-supported Texas Advanced Computing Center.
A key to the model was the incorporation of data on a multitude of scales. "Many natural processes display a multitude of phenomena on a wide range of scales, from small to large," Gurnis explains. For example, at the largest scale -- that of the whole earth -- the movement of the surface tectonic plates is a manifestation of a giant heat engine, driven by the convection of the mantle below. The boundaries between the plates, however, are composed of many hundreds to thousands of individual faults, which together constitute active fault zones. "The individual fault zones play a critical role in how the whole planet works," he says, "and if you can't simulate the fault zones, you can't simulate plate movement" -- and, in turn, you can't simulate the dynamics of the whole planet.
In the new model, the researchers were able to resolve the largest fault zones, creating a mesh with a resolution of about one kilometer near the plate boundaries. Included in the simulation were seismological data as well as data pertaining to the temperature of the rocks, their density, and their viscosity -- or how strong or weak the rocks are, which affects how easily they deform. That deformation is nonlinear -- with simple changes producing unexpected and complex effects.
"Normally, when you hit a baseball with a bat, the properties of the bat don't change -- it won't turn to Silly Putty. In the earth, the properties do change, which creates an exciting computational problem," says Gurnis. "If the system is too nonlinear, the earth becomes too mushy; if it's not nonlinear enough, plates won't move. We need to hit the 'sweet spot.'"
After crunching through the data for 100,000 hours of processing time per run, the model returned an estimate of the motion of both large tectonic plates and smaller microplates -- including their speed and direction. The results were remarkably close to observed plate movements.
In fact, the investigators discovered that anomalous rapid motion of microplates emerged from the global simulations. "In the western Pacific," Gurnis says, "we have some of the most rapid tectonic motions seen anywhere on Earth, in a process called 'trench rollback.' For the first time, we found that these small-scale tectonic motions emerged from the global models, opening a new frontier in geophysics."
One surprising result from the model relates to the energy released from plates in earthquake zones. "It had been thought that the majority of energy associated with plate tectonics is released when plates bend, but it turns out that's much less important than previously thought," Gurnis says. "Instead, we found that much of the energy dissipation occurs in the earth's deep interior. We never saw this when we looked on smaller scales."
Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by California Institute of Technology.
Journal Reference:
- G. Stadler, M. Gurnis, C. Burstedde, L. C. Wilcox, L. Alisic, O. Ghattas. The Dynamics of Plate Tectonics and Mantle Flow: From Local to Global Scales. Science, 2010; 329 (5995): 1033 DOI: 10.1126/science.1191223
Sunday, August 29, 2010
Shrinking Atmospheric Layer
Shrinking Atmospheric Layer Linked to Low Levels of Solar Radiation
Large changes in the sun's energy output may drive unexpectedly dramatic fluctuations in Earth's outer atmosphere.
Results of a new study link a recent, temporary shrinking of a high atmospheric layer with a sharp drop in the sun's ultraviolet radiation levels.
The research, led by scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., and the University of Colorado at Boulder (CU), indicates that the sun's magnetic cycle, which produces differing numbers of sunspots over an approximately 11-year cycle, may vary more than previously thought.
The results, published in the American Geophysical Union journalGeophysical Research Letters, are funded by NASA and by the National Science Foundation (NSF), NCAR's sponsor.
"This research makes a compelling case for the need to study the coupled sun-Earth system," says Farzad Kamalabadi, program director in NSF's Division of Atmospheric and Geospace Sciences, "and to illustrate the importance of solar influences on our terrestrial environment with both fundamental scientific implications and societal consequences."
The findings may have implications for orbiting satellites, as well as for the International Space Station.
"Our work demonstrates that the solar cycle not only varies on the typical 11-year time scale, but also can vary from one solar minimum to another," says lead author Stanley Solomon, a scientist at NCAR's High Altitude Observatory. "All solar minima are not equal."
The fact that the layer in the upper atmosphere known as the thermosphere is shrunken and dense means that satellites can more easily maintain their orbits.
But it also indicates that space debris and other objects that pose hazards may persist longer in the thermosphere.
"With lower thermospheric density, our satellites will have a longer life in orbit," says CU professor Thomas Woods, a co-author.
"This is good news for those satellites that are actually operating, but it is also bad because of the thousands of non-operating objects remaining in space that could potentially have collisions with our working satellites."
The sun's energy output declined to unusually low levels from 2007 to 2009, a particularly prolonged solar minimum during which there were virtually no sunspots or solar storms.
During that same period of low solar activity, Earth's thermosphere shrank more than at any time in the 43-year era of space exploration.
The thermosphere, which ranges in altitude from about 55 to more than 300 miles (90 to 500 kilometers), is a rarified layer of gas at the edge of space where the sun's radiation first makes contact with Earth's atmosphere.
It typically cools and becomes less dense during low solar activity.
But the magnitude of the density change during the recent solar minimum appeared to be about 30 percent greater than would have been expected by low solar activity.
The study team used computer modeling to analyze two possible factors implicated in the mystery of the shrinking thermosphere.
They simulated both the impacts of solar output and the role of carbon dioxide, a potent greenhouse gas that, according to past estimates, is reducing the density of the outer atmosphere by about 2 percent to 5 percent per decade.
Their work built on several recent studies.
Earlier this year, a team of scientists from the Naval Research Laboratory and George Mason University, measuring changes in satellite drag, estimated that the density of the thermosphere declined in 2007-09 to about 30 percent less than during the previous solar minimum in 1996.
Other studies by scientists at the University of Southern California and CU, using measurements from sub-orbital rocket flights and space-based instruments, have estimated that levels of extreme-ultraviolet radiation-a class of photons with extremely short wavelengths-dropped about 15 percent during the same period.
However, scientists remained uncertain whether the decline in extreme-ultraviolet radiation would be sufficient to have such a dramatic impact on the thermosphere, even when combined with the effects of carbon dioxide.
To answer this question, Solomon and his colleagues turned to an NCAR computer tool, known as the Thermosphere-Ionosphere-Electrodynamics General Circulation Model.
They used the model to simulate how the sun's output during 1996 and 2008 would affect the temperature and density of the thermosphere.
They also created two simulations of thermospheric conditions in 2008-one with a level that approximated actual carbon dioxide emissions and one with a fixed, lower level.
The results showed the thermosphere cooling in 2008 by 41 kelvins, or K (about 74 degrees Fahrenheit) compared to 1996, with just 2 K attributable to the carbon dioxide increase.
The results also showed the thermosphere's density decreasing by 31 percent, with just 3 percent attributable to carbon dioxide, and closely approximated the 30 percent reduction in density indicated by measurements of satellite drag.
"It is now clear that the record low temperature and density were primarily caused by unusually low levels of solar radiation at the extreme-ultraviolet level," Solomon says.
Woods says the research indicates that the sun could be going through a period of relatively low activity, similar to periods in the early 19th and 20th centuries.
This could mean that solar output may remain at a low level for the near future.
"If it is indeed similar to certain patterns in the past, then we expect to have low solar cycles for the next 10 to 30 years," Woods says.
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by National Science Foundation.
Journal Reference:
- Stanley C. Solomon, Thomas N. Woods, Leonid V. Didkovsky, John T. Emmert, Liying Qian. Anomalously low solar extreme-ultraviolet irradiance and thermospheric density during solar minimum.Geophysical Research Letters, 2010; 37 (16): L16103 DOI:10.1029/2010GL044468
El Niños Are Growing Stronger
El Niños Are Growing Stronger, NASA/NOAA Study Finds
A relatively new type of El Niño, which has its warmest waters in the central-equatorial Pacific Ocean, rather than in the eastern-equatorial Pacific, is becoming more common and progressively stronger, according to a new study by NASA and NOAA. The research may improve our understanding of the relationship between El Niños and climate change, and has potentially significant implications for long-term weather forecasting.
Lead author Tong Lee of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and Michael McPhaden of NOAA's Pacific Marine Environmental Laboratory, Seattle, measured changes in El Niño intensity since 1982. They analyzed NOAA satellite observations of sea surface temperature, checked against and blended with directly-measured ocean temperature data. The strength of each El Niño was gauged by how much its sea surface temperatures deviated from the average. They found the intensity of El Niños in the central Pacific has nearly doubled, with the most intense event occurring in 2009-10.
The scientists say the stronger El Niños help explain a steady rise in central Pacific sea surface temperatures observed over the past few decades in previous studies-a trend attributed by some to the effects of global warming. While Lee and McPhaden observed a rise in sea surface temperatures during El Niño years, no significant temperature increases were seen in years when ocean conditions were neutral, or when El Niño's cool water counterpart, La Niña, was present.
"Our study concludes the long-term warming trend seen in the central Pacific is primarily due to more intense El Niños, rather than a general rise of background temperatures," said Lee.
"These results suggest climate change may already be affecting El Niño by shifting the center of action from the eastern to the central Pacific," said McPhaden. "El Niño's impact on global weather patterns is different if ocean warming occurs primarily in the central Pacific, instead of the eastern Pacific.
"If the trend we observe continues," McPhaden added, "it could throw a monkey wrench into long-range weather forecasting, which is largely based on our understanding of El Niños from the latter half of the 20th century."
El Niño, Spanish for "the little boy," is the oceanic component of a climate pattern called the El Niño-Southern Oscillation, which appears in the tropical Pacific Ocean on average every three to five years. The most dominant year-to-year fluctuating pattern in Earth's climate system, El Niños have a powerful impact on the ocean and atmosphere, as well as important socioeconomic consequences. They can influence global weather patterns and the occurrence and frequency of hurricanes, droughts and floods; and can even raise or lower global temperatures by as much as 0.2 degrees Celsius (0.4 degrees Fahrenheit).
During a "classic" El Niño episode, the normally strong easterly trade winds in the tropical eastern Pacific weaken. That weakening suppresses the normal upward movement of cold subsurface waters and allows warm surface water from the central Pacific to shift toward the Americas. In these situations, unusually warm surface water occupies much of the tropical Pacific, with the maximum ocean warming remaining in the eastern-equatorial Pacific.
Since the early 1990s, however, scientists have noted a new type of El Niño that has been occurring with greater frequency. Known variously as "central-Pacific El Niño," "warm-pool El Niño," "dateline El Niño" or "El Niño Modoki" (Japanese for "similar but different"), the maximum ocean warming from such El Niños is found in the central-equatorial, rather than eastern, Pacific. Such central Pacific El Niño events were observed in 1991-92, 1994-95, 2002-03, 2004-05 and 2009-10. A recent study found many climate models predict such events will become much more frequent under projected global warming scenarios.
Lee said further research is needed to evaluate the impacts of these increasingly intense El Niños and determine why these changes are occurring. "It is important to know if the increasing intensity and frequency of these central Pacific El Niños are due to natural variations in climate or to climate change caused by human-produced greenhouse gas emissions," he said.
Results of the study were published recently in Geophysical Research Letters.
For more information on El Niño, visit:http://sealevel.jpl.nasa.gov/.
Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA/Jet Propulsion Laboratory.
Distant Star's Sound Waves Reveal Cycle Similar to the Sun's
In a bid to unlock longstanding mysteries of the Sun, including the impacts on Earth of its 11-year cycle, an international team of scientists has successfully probed a distant star. By monitoring the star's sound waves, the team has observed a magnetic cycle analogous to the Sun's solar cycle.
The study, conducted by scientists at the National Center for Atmospheric Research (NCAR) and colleagues in France and Spain, is being published in Science.
The scientists studied a star known as HD49933, which is located 100 light years from Earth in the constellation Monoceros, the Unicorn, just east of Orion. The team examined the star's acoustic fluctuations, using a technique called "stellar seismology." They detected the signature of "starspots," areas of intense magnetic activity on the surface that are similar to sunspots. While scientists have previously observed these magnetic cycles in other stars, this was the first time they have discovered such a cycle using stellar seismology.
"Essentially, the star is ringing like a bell," says NCAR scientist Travis Metcalfe, a co-author of the new study. "As it moves through its starspot cycle, the tone and volume of the ringing changes in a very specific pattern, moving to higher tones with lower volume at the peak of its magnetic cycle."
"We've discovered a magnetic activity cycle in this star, similar to what we see with the Sun," says co-author and NCAR scientist Savita Mathur. "This technique of listening to the stars will allow us to examine potentially hundreds of stars."
The team hopes to assess the potential for other stars in our galaxy to host planets, including some perhaps capable of sustaining life.
"Understanding the activity of stars harboring planets is necessary because magnetic conditions on the star's surface could influence the habitable zone, where life could develop," says CEA-Saclay scientist Rafael Garcia, the study's lead author.
Studying many stars with stellar seismology could help scientists better understand how magnetic activity cycles can differ from star to star, as well as the processes behind such cycles. The work could especially shed light on the magnetic processes that go on within the Sun, furthering our understanding of its influence on Earth's climate. It may also lead to better predictions of the solar cycle and resulting geomagnetic storms that can cause major disruption to power grids and communication networks.
In addition to NCAR, the team's scientists are from France's Center for Nuclear Studies of Saclay (CEA-Saclay), Paris/Meudon Observatory (OPM), the University of Toulouse, and Spain's Institute of Astrophysics of the Canaries (IAC). The research was funded by the National Science Foundation, which is NCAR's sponsor, the CEA, the French Stellar Physics National Research Plan, and the Spanish National Research Plan.
Classifying stars
The scientists examined 187 days of data captured by the international Convection Rotation and Planetary Transits (CoRoT) space mission.
Launched on December 27, 2006, CoRoT was developed and is operated by the French National Center for Space Studies (CNES) with contributions from Austria, Belgium, Brazil, Germany, Spain, and the European Space Agency. CoRoT is equipped with a 27-centimeter (11-inch) diameter telescope and a 4-CCD (charge-coupled device) camera sensitive to tiny variations in the light intensity from stars.
The study authors found that HD49933 is much bigger and hotter than the Sun, and its magnetic cycle is much shorter. Whereas past surveys of stars have found cycles similar to the 11-year cycle of the Sun, this star has a cycle of less than a year.
This short cycle is important to scientists because it may enable them to observe an entire cycle more quickly, thereby gleaning more information about magnetic patterns than if they could only observe part of a longer cycle.
The scientists plan to expand their observations by using other stars observed by CoRoT as well as data from NASA's Kepler mission, launched in March 2009. Kepler is seeking Earth-sized planets to survey. The mission will provide continuous data over three to five years from hundreds of stars that could be hosting planets.
"If it turns out that a short magnetic cycle is common in stars, then we will potentially observe a large number of full cycles during Kepler's mission," says Metcalfe. "The more stars and complete magnetic cycles we have to observe, the more we can place the Sun into context and explore the impacts of magnetic activity on possible planets hosted by these stars."
The team has spent the past six months exploring the structure and dynamics of HD49933 and classifying its size. They will next verify their observations using ground-based telescopes to confirm the magnetic activity of the star. When the star reemerges from behind the Sun in September, they hope to measure the full length of the cycle. The CoRoT mission was designed to collect up to 150 days of continuous data at a time, which was not enough to determine the exact length of the star's cycle.
Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by National Center for Atmospheric Research/University Corporation for Atmospheric Research.
Journal Reference:
- Rafael A. García, Savita Mathur, David Salabert, Jérôme Ballot, Clara Régulo, Travis S. Metcalfe, and Annie Baglin.CoRoT Reveals a Magnetic Activity Cycle in a Sun-Like Star. Science, 2010; 329 (5995): 1032 DOI:10.1126/science.1191064
Tuesday, June 8, 2010
Recycling Without Sorting
Recycling Without Sorting
Engineers Create Recycling Plant That Removes The Need To Sort
---------------------------------------------------------------------------------Engineers use the term single-stream recycling for their plant that takes the sorting out of the public’s hands. Trucks dump an unsorted mess of paper, plastic, and metal onto a conveyor belt. Magnets, air blowers, and optical scanners separate the items, making it possible to recycle the different products.
Recycling programs have been underway for years, but Americans still lag behind on recycling efforts. The biggest reason -- it's inconvenient.
If you recycle, you know the drill ... separate ... separate ... separate ...
"In the early years, we've had to separate things fairly significantly," recycler Steve Snowden says.
Now, Snowden's separating days are over. A new program called "Single Stream Recycling" allows you to put all recycle items into one container.
"We like it quite a bit because it is so easy," Snowden says.
Leaving the rest of the work up to someone else!
"We do the separation to mechanically separate the materials here at the recycling facility," says Michael Taylor, environmental scientist from Waste Management Recycle America, who developed the system.
Fast, rotating devices separate newspaper and cardboard from cans and glass that tumble to another level. Magnets grab metal cans and optical scanners recognize plastic from other items and trigger blasts of air to blow plastic into another bin.
"Highly-engineered, highly complex mechanical systems do the work in a much more efficient, much more cost effective and much more significantly faster-paced environment," Taylor explains.
Environmental scientists have seen an increase in recycling of almost 30-percent among homeowners who use the system.
"We're much more liable to do something the easier it is to do it," Snowden says.
There are 27 Waste Management Recycle America "Single Stream Recycling" facilities in the country. There are also other recycling organizations that use Single Stream.
The Materials Research Society and the Optical Society of America contributed to the information contained in the TV portion of this report.
PROS AND CONS: If residents don't have to maintain separate containers for their glass, bottles, paper and plastic supporters of the plant say that this encourages more people to participate in recycling. Residents can simply load all recyclables into a single container to be sorted at the plant. It also reduces costs for local governments, because less expensive trucks can be used if the waste material isn't sorted beforehand. Trucks cost $50,000 each more equipment to keep paper and other materials separate, for example. Critics say such a single-stream plant is inefficient and diminishes the usefulness of the materials collected, because it opts for speed to process the vast quantities of mixed recyclable waste it receives. There is more contamination as a result, which degrades the quality of what is sorted.
HOW IT WORKS: The plant uses a variety of sorting devices, including screens, magnets and ultraviolet optical scanners that trigger blasts of air to separate plastic bottles from the rest of the items, as well as spinning, star-shaped plastic devices that separate newspaper from cans and bottles by pushing the paper higher up an inclined screen so the heavier, smaller cans and bottles tumble down to a lower level. Glass is sorted by color and crushed, while plastic is shredded into small chips.
RECYCLING TIPS:
* Recycle all paper (junk mail, boxes, magazines, envelopes), bottles and cans (aluminum, glass, metal, and plastic).
* Buy products with little or no packaging, and buy the largest size you can use.
* Buy reusable products such as non-disposable cameras, electric razors, reusable lunch boxes, etc.
* Bring your own mug to the office or local coffee house for coffee; paper cups waste both money and landfill space.
* Buy products made with recycled materials.
* Reduce your junk mail by canceling unwanted catalogs.
* Bring your own reusable grocery sacks when shopping at the local supermarket.
Revolutionary New Desalination Membrane
Salt stacks at a desalination plant in Trapani, Sicily (Italy). (Credit: iStockphoto/Beat Bieler)
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Hold the Salt: Engineers Develop Revolutionary New Desalination Membrane.
-----------------------------------------------------------------------------------------------------------Researchers from the UCLA Henry Samueli School of Engineering and Applied Science have unveiled a new class of reverse-osmosis membranes for desalination that resist the clogging which typically occurs when seawater, brackish water and waste water are purified.
The highly permeable, surface-structured membrane can easily be incorporated into today's commercial production system, the researchers say, and could help to significantly reduce desalination operating costs. Their findings appear in the current issue of the Journal of Materials Chemistry.
Reverse-osmosis (RO) desalination uses high pressure to force polluted water through the pores of a membrane. While water molecules pass through the pores, mineral salt ions, bacteria and other impurities cannot. Over time, these particles build up on the membrane's surface, leading to clogging and membrane damage. This scaling and fouling places higher energy demands on the pumping system and necessitates costly cleanup and membrane replacement.
The new UCLA membrane's novel surface topography and chemistry allow it to avoid such drawbacks.
"Besides possessing high water permeability, the new membrane also shows high rejection characteristics and long-term stability," said Nancy H. Lin, a UCLA Engineering senior researcher and the study's lead author. "Structuring the membrane surface does not require a long reaction time, high reaction temperature or the use of a vacuum chamber. The anti-scaling property, which can increase membrane life and decrease operational costs, is superior to existing commercial membranes."
The new membrane was synthesized through a three-step process. First, researchers synthesized a polyamide thin-film composite membrane using conventional interfacial polymerization. Next, they activated the polyamide surface with atmospheric pressure plasma to create active sites on the surface. Finally, these active sites were used to initiate a graft polymerization reaction with a monomer solution to create a polymer "brush layer" on the polyamide surface. This graft polymerization is carried out for a specific period of time at a specific temperature in order to control the brush layer thickness and topography.
"In the early years, surface plasma treatment could only be accomplished in a vacuum chamber," said Yoram Cohen, UCLA professor of chemical and biomolecular engineering and a corresponding author of the study. "It wasn't practical for large-scale commercialization because thousands of meters of membranes could not be synthesized in a vacuum chamber. It's too costly. But now, with the advent of atmospheric pressure plasma, we don't even need to initiate the reaction chemically. It's as simple as brushing the surface with plasma, and it can be done for almost any surface."
In this new membrane, the polymer chains of the tethered brush layer are in constant motion. The chains are chemically anchored to the surface and are thus more thermally stable, relative to physically coated polymer films. Water flow also adds to the brush layer's movement, making it extremely difficult for bacteria and other colloidal matter to anchor to the surface of the membrane.
"If you've ever snorkeled, you'll know that sea kelp move back and forth with the current or water flow," Cohen said. "So imagine that you have this varied structure with continuous movement. Protein or bacteria need to be able to anchor to multiple spots on the membrane to attach themselves to the surface -- a task which is extremely difficult to attain due to the constant motion of the brush layer. The polymer chains protect and screen the membrane surface underneath."
Another factor in preventing adhesion is the surface charge of the membrane. Cohen's team is able to choose the chemistry of the brush layer to impart the desired surface charge, enabling the membrane to repel molecules of an opposite charge.
The team's next step is to expand the membrane synthesis into a much larger, continuous process and to optimize the new membrane's performance for different water sources.
"We want to be able to narrow down and create a membrane selection system for different water sources that have different fouling tendencies," Lin said. "With such knowledge, one can optimize the membrane surface properties with different polymer brush layers to delay or prevent the onset of membrane fouling and scaling.
"The cost of desalination will therefore decrease when we reduce the cost of chemicals [used for membrane cleaning], as well as process operation [for membrane replacement]. Desalination can become more economical and used as a viable alternate water resource."
Cohen's team, in collaboration with the UCLA Water Technology Research (WaTeR) Center, is currently carrying out specific studies to test the performance of the new membrane's fouling properties under field conditions.
"We work directly with industry and water agencies on everything that we're doing here in water technology," Cohen said. "The reason for this is simple: If we are to accelerate the transfer of knowledge technology from the university to the real world, where those solutions are needed, we have to make sure we address the real issues. This also provides our students with a tremendous opportunity to work with industry, government and local agencies."
A paper providing a preliminary introduction to the new membrane also appeared in the Journal of Membrane Science last month.
The original article was written by Wileen Wong Kromhout.
Journal References:
- Nancy H. Lin, Myung-man Kim, Gregory T. Lewis, Yoram Cohen. Polymer surface nano-structuring of reverse osmosis membranes for fouling resistance and improved flux performance. Journal of Materials Chemistry, 2010; DOI: 10.1039/b926918e
- Myung-man Kim, Nancy H. Lin, Gregory T. Lewis, Yoram Cohen. Surface nano-structuring of reverse osmosis membranes via atmospheric pressure plasma-induced graft polymerization for reduction of mineral scaling propensity. Journal of Membrane Science, 2010; DOI: 10.1016/j.memsci.2010.02.053
Life on Titan?
Life on Titan? New Clues to What's Consuming Hydrogen, Acetylene on Saturn's Moon.
----------------------------------------------------------------------------------------------------------------- Two new papers based on data from NASA's Cassini spacecraft scrutinize the complex chemical activity on the surface of Saturn's moon Titan. While non-biological chemistry offers one possible explanation, some scientists believe these chemical signatures bolster the argument for a primitive, exotic form of life or precursor to life on Titan's surface. According to one theory put forth by astrobiologists, the signatures fulfill two important conditions necessary for a hypothesized "methane-based life."
One key finding comes from a paper online now in the journal Icarus that shows hydrogen molecules flowing down through Titan's atmosphere and disappearing at the surface. Another paper online now in the Journal of Geophysical Research maps hydrocarbons on the Titan surface and finds a lack of acetylene.
This lack of acetylene is important because that chemical would likely be the best energy source for a methane-based life on Titan, said Chris McKay, an astrobiologist at NASA Ames Research Center, Moffett Field, Calif., who proposed a set of conditions necessary for this kind of methane-based life on Titan in 2005. One interpretation of the acetylene data is that the hydrocarbon is being consumed as food. But McKay said the flow of hydrogen is even more critical because all of their proposed mechanisms involved the consumption of hydrogen.
"We suggested hydrogen consumption because it's the obvious gas for life to consume on Titan, similar to the way we consume oxygen on Earth," McKay said. "If these signs do turn out to be a sign of life, it would be doubly exciting because it would represent a second form of life independent from water-based life on Earth."
To date, methane-based life forms are only hypothetical. Scientists have not yet detected this form of life anywhere, though there are liquid-water-based microbes on Earth that thrive on methane or produce it as a waste product. On Titan, where temperatures are around 90 Kelvin (minus 290 degrees Fahrenheit), a methane-based organism would have to use a substance that is liquid as its medium for living processes, but not water itself. Water is frozen solid on Titan's surface and much too cold to support life as we know it.
The list of liquid candidates is very short: liquid methane and related molecules like ethane. While liquid water is widely regarded as necessary for life, there has been extensive speculation published in the scientific literature that this is not a strict requirement.
The new hydrogen findings are consistent with conditions that could produce an exotic, methane-based life form, but do not definitively prove its existence, said Darrell Strobel, a Cassini interdisciplinary scientist based at Johns Hopkins University in Baltimore, Md., who authored the paper on hydrogen.
Strobel, who studies the upper atmospheres of Saturn and Titan, analyzed data from Cassini's composite infrared spectrometer and ion and neutral mass spectrometer in his new paper. The paper describes densities of hydrogen in different parts of the atmosphere and the surface. Previous models had predicted that hydrogen molecules, a byproduct of ultraviolet sunlight breaking apart acetylene and methane molecules in the upper atmosphere, should be distributed fairly evenly throughout the atmospheric layers.
Strobel found a disparity in the hydrogen densities that lead to a flow down to the surface at a rate of about 10,000 trillion trillion hydrogen molecules per second. This is about the same rate at which the molecules escape out of the upper atmosphere.
"It's as if you have a hose and you're squirting hydrogen onto the ground, but it's disappearing," Strobel said. "I didn't expect this result, because molecular hydrogen is extremely chemically inert in the atmosphere, very light and buoyant. It should 'float' to the top of the atmosphere and escape."
Strobel said it is not likely that hydrogen is being stored in a cave or underground space on Titan. The Titan surface is also so cold that a chemical process that involved a catalyst would be needed to convert hydrogen molecules and acetylene back to methane, even though overall there would be a net release of energy. The energy barrier could be overcome if there were an unknown mineral acting as the catalyst on Titan's surface.
The hydrocarbon mapping research, led by Roger Clark, a Cassini team scientist based at the U.S. Geological Survey in Denver, examines data from Cassini's visual and infrared mapping spectrometer. Scientists had expected the sun's interactions with chemicals in the atmosphere to produce acetylene that falls down to coat the Titan surface. But Cassini detected no acetylene on the surface.
In addition Cassini's spectrometer detected an absence of water ice on the Titan surface, but loads of benzene and another material, which appears to be an organic compound that scientists have not yet been able to identify. The findings lead scientists to believe that the organic compounds are shellacking over the water ice that makes up Titan's bedrock with a film of hydrocarbons at least a few millimeters to centimeters thick, but possibly much deeper in some places. The ice remains covered up even as liquid methane and ethane flow all over Titan's surface and fill up lakes and seas much as liquid water does on Earth.
"Titan's atmospheric chemistry is cranking out organic compounds that rain down on the surface so fast that even as streams of liquid methane and ethane at the surface wash the organics off, the ice gets quickly covered again," Clark said. "All that implies Titan is a dynamic place where organic chemistry is happening now."
The absence of detectable acetylene on the Titan surface can very well have a non-biological explanation, said Mark Allen, principal investigator with the NASA Astrobiology Institute Titan team. Allen is based at NASA's Jet Propulsion Laboratory in Pasadena, Calif. Allen said one possibility is that sunlight or cosmic rays are transforming the acetylene in icy aerosols in the atmosphere into more complex molecules that would fall to the ground with no acetylene signature.
"Scientific conservatism suggests that a biological explanation should be the last choice after all non-biological explanations are addressed," Allen said. "We have a lot of work to do to rule out possible non-biological explanations. It is more likely that a chemical process, without biology, can explain these results -- for example, reactions involving mineral catalysts."
"These new results are surprising and exciting," said Linda Spilker, Cassini project scientist at JPL. "Cassini has many more flybys of Titan that might help us sort out just what is happening at the surface."
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL.
For more information about the Cassini-Huygens mission visit http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov
Journal References:
- Darrell F. Strobel. Molecular hydrogen in Titan's atmosphere: Implications of the measured tropospheric and thermospheric mole fractions. Icarus, 2010; DOI: 10.1016/j.icarus.2010.03.003
- Clark, R. N., J. M. Curchin, J. W. Barnes, R. Jaumann, L. Soderblom, D. P. Cruikshank, R. H. Brown, S. Rodriguez, J. Lunine, K. Stephan, T. M. Hoefen, S. Le Mouelic, C. Sotin, K. H. Baines, B. J. Buratti, and P. D. Nicholson. Detection and Mapping of Hydrocarbon Deposits on Titan. Journal of Geophysical Research, 2010; (in press) DOI: 10.1029/2009JE003369
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