In the study, MacLeod examined fossils of organisms that lived 90 million years ago. This photo is an image from a Scanning electron microscope of a planktic (left) and benthic (right) foraminifera from Tanzania. Both shells are less than 0.5 millimeters across. (Credit: University of Missouri)
For years, scientists have thought that a continental ice sheet formed during the Late Cretaceous Period more than 90 million years ago when the climate was much warmer than it is today. Now, a University of Missouri researcher has found evidence suggesting that no ice sheet formed at this time. This finding could help environmentalists and scientists predict what Earth’s climate will be as carbon dioxide levels continue to rise.
“Currently, carbon dioxide levels are just above 400 parts per million (ppm), up approximately 120 ppm in the last 150 years and rising about 2 ppm each year,” said Ken MacLeod, a professor of geological sciences at MU. “In our study, we found that during the Late Cretaceous Period, when carbon dioxide levels were around 1,000 ppm, there were no continental ice sheets on earth. So, if carbon dioxide levels continue to rise, the Earth will be ice-free once the climate comes into balance with the higher levels.”
In his study, MacLeod analyzed the fossilized shells of 90 million-year-old planktic and benthic foraminifera, single-celled organisms about the size of a grain of salt. Measuring the ratios of different isotopes of oxygen and carbon in the fossils gives scientists information about past temperatures and other environmental conditions. The fossils, which were found in Tanzania, showed no evidence of cooling or changes in local water chemistry that would have been expected if a glacial event had occurred during that time period.
“We know that the carbon dioxide (CO2) levels are rising currently and are at the highest they have been in millions of years. We have records of how conditions have changed as CO2 levels have risen from 280 to 400 ppm, but I believe it also is important to know what could happen when those levels reach 600 to 1000 ppm,” MacLeod said. “At the rate that carbon dioxide levels are rising, we will reach 600 ppm around the end of this century. At that level of CO2, will ice sheets on Greenland and Antarctica be stable? If not, how will their melting affect the planet?”
Previously, many scientists have thought that doubling CO2 levels would cause earth’s temperature to increase as much as 3 degrees Celsius, or approximately 6 degrees Fahrenheit. However, the temperatures MacLeod believes existed in Tanzania 90 million years ago are more consistent with predictions that a doubling of CO2 levels would cause Earth’s temperature could rise an average of 6 degrees Celsius, or approximately 11 degrees Fahrenheit.
“While studying the past can help us predict the future, other challenges with modern warming still exist,” MacLeod said. “The Late Cretaceous climate was very warm, but the Earth adjusted as changes occurred over millions of years. We’re seeing the same size changes, but they are happening over a couple of hundred years, maybe 10,000 times faster. How that affects the equation is a big and difficult question.”
MacLeod’s study was published in the October issue of the journal Geology.
Note : The above story is based on materials provided by University of Missouri-Columbia.
Some of the rocks that Crowe and his colleagues studied. (Credit: Nic Beukes)
Oxygen appeared in the atmosphere up to 700 million years earlier than we previously thought, according to research published today in the journal Nature, raising new questions about the evolution of early life.
Researchers from the University of Copenhagen and University of British Columbia examined the chemical composition of three-billion-year-old soils from South Africa — the oldest soils on Earth — and found evidence for low concentrations of atmospheric oxygen. Previous research indicated that oxygen began accumulating in the atmosphere only about 2.3 billion years ago during a dynamic period in Earth’s history referred to as the Great Oxygenation Event.
“We’ve always known that oxygen production by photosynthesis led to the eventual oxygenation of the atmosphere and the evolution of aerobic life,” says Sean Crowe, co-lead author of the study and an assistant professor in the Departments of Microbiology and Immunology, and Earth, Ocean and Atmospheric Sciences at UBC.
“This study now suggests that the process began very early in Earth’s history, supporting a much greater antiquity for oxygen producing photosynthesis and aerobic life,” says Crowe, who conducted the research while a post-doctoral fellow at Nordic Center for Earth Evolution at the University of Southern Denmark in partnership with the centre’s director Donald Canfield.
There was no oxygen in the atmosphere for at least hundreds of millions of years after Earth formed. Today, Earth’s atmosphere is 20 per cent oxygen thanks to photosynthetic bacteria that, like trees and other plants, consume carbon dioxide and release oxygen. The bacteria laid the foundation for oxygen breathing organisms to evolve and inhabit the planet.
“These findings imply that it took a very long time for geological and biological processes to conspire and produce the oxygen rich atmosphere we now enjoy,” says Lasse Døssing, the other lead scientist on the study, from the University of Copenhagen.
Note : The above story is based on materials provided by University of British Columbia.
Ring-formation between belts: Model showing third radiation ring (red). Recent observations by NASA’s Van Allen Probes mission showed an event in which three radiation zones were observed at extremely high energies, including an unusual medium narrow ring (red) that existed for approximately four weeks. The modeling results, displayed in this illustration, revealed that for particles at these high energies, different physical processes are responsible for the acceleration and loss of electrons in the radiation belts, which explains the formation of the unusual long-lived ring between the belts. The discovery will help protect satellites form the harmful radiation in space, UCLA scientists report. (Credit: Yuri Shprits, Adam Kellerman, Dmitri Subbotin/UCLA)
Since the discovery of the Van Allen radiation belts in 1958, space scientists have believed these belts encircling Earth consist of two doughnut-shaped rings of highly charged particles — an inner ring of high-energy electrons and energetic positive ions and an outer ring of high-energy electrons.
In February of this year, a team of scientists reported the surprising discovery of a previously unknown third radiation ring — a narrow one that briefly appeared between the inner and outer rings in September 2012 and persisted for a month.
In new research, UCLA space scientists have successfully modeled and explained the unprecedented behavior of this third ring, showing that the extremely energetic particles that made up this ring, known as ultra-relativistic electrons, are driven by very different physics than typically observed Van Allen radiation belt particles. The region the belts occupy — ranging from about 1,000 to 50,000 kilometers above Earth’s surface — is filled with electrons so energetic they move close to the speed of light.
“In the past, scientists thought that all the electrons in the radiation belts around the Earth obeyed the same physics,” said Yuri Shprits, a research geophysicist with the UCLA Department of Earth and Space Sciences. “We are finding now that radiation belts consist of different populations that are driven by very different physical processes.”
Shprits, who is also an associate professor at Russia’s Skolkovo Institute of Science and Technology, a new university co-organized by MIT, led the study, which is published Sept. 22 in the journal Nature Physics.
The Van Allen belts can pose a severe danger to satellites and spacecraft, with hazards ranging from minor anomalies to the complete failure of critical satellites. A better understanding of the radiation in space is instrumental to protecting people and equipment, Shprits said.
Ultra-relativistic electrons — which made up the third ring and are present in both the outer and inner belts — are especially hazardous and can penetrate through the shielding of the most protected and most valuable satellites in space, noted Shprits and Adam Kellerman, a staff research associate in Shprits’ group.
“Their velocity is very close to the speed of light, and the energy of their motion is several times larger than the energy contained in their mass when they are at rest,” Kellerman said. “The distinction between the behavior of the ultra-relativistic electrons and those at lower energies was key to this study.” Shprits and his team found that on Sept. 1, 2012, plasma waves produced by ions that do not typically affect energetic electrons “whipped out ultra-relativistic electrons in the outer belt almost down to the inner edge of the outer belt.” Only a narrow ring of ultra-relativistic electrons survived this storm. This remnant formed the third ring.
After the storm, a cold bubble of plasma around Earth expanded to protect the particles in the narrow ring from ion waves, allowing the ring to persist. Shprits’ group also found that very low-frequency electromagnetic pulsations that were thought to be dominant in accelerating and losing radiation belt electrons did not influence the ultra-relativistic electrons.
The Van Allen radiation belts “can no longer be considered as one consistent mass of electrons. They behave according to their energies and react in various ways to the disturbances in space,” said Shprits, who was honored by President Obama last July with a Presidential Early Career Award for Scientists and Engineers.
“Ultra-relativistic particles move very fast and cannot be at the right frequency with waves when they are close to the equatorial plane,” said Ksenia Orlova, a UCLA postdoctoral scholar in Shprits’ group who is funded by NASA’s Jack Eddy Fellowship. “This is the main reason the acceleration and scattering into the atmosphere of ultra-relativistic electrons by these waves is less efficient.”
“This study shows that completely different populations of particles exist in space that change on different timescales, are driven by different physics and show very different spatial structures,” Shprits said.
The team performed simulations with a model of Earth’s radiation belts for the period from late August 2012 to early October 2012. The simulation, conducted using the physics of ultra-relativistic electrons and space weather conditions monitored by ground stations, matched the observations from NASA’s Van Allen Probes mission extraordinarily well, confirming the team’s theory about the new ring.
“We have a remarkable agreement between our model and observations, both encompassing a wide range of energies,” said Dmitriy Subbotin, a former graduate student of Shprits and current UCLA staff research associate.
“I believe that, with this study, we have uncovered the tip of the iceberg,” Shprits said. “We still need to fully understand how these electrons are accelerated, where they originate and how the dynamics of the belts is different for different storms.”
Earth’s radiation belts were discovered in 1958 by Explorer I, the first U.S. satellite that traveled to space.
Note : The above story is based on materials provided by University of California – Los Angeles.
Bands of glowing magma, about 2,200 degrees Fahrenheit, are exposed as a pillow lava tube extrudes down slope. Credit: NOAA/National Science Foundation
A team of researchers from Wellington University in New Zealand has found that volcanoes that erupt beneath bodies of water can cause widespread dispersal of diatoms found in their beds. In their paper published in the journal Geology, the researchers describe how they analyzed soil samples from islands where ash was believed to have landed after an ancient volcanic eruption. They report finding diatoms that match those found in the lake that formed after the volcano erupted.
Diatoms are a type of brown algae with one unique attribute—they have glass shells—the result of living in silica rich environments. And while there are numerous species all over the world, there is one that is unique to a lake bottom on New Zealand’s North Island (formed after the ancient Taupo volcano erupted). Because of that uniqueness, the researchers wondered if it might be possible to track the algae, if they had been blown into the atmosphere when Taupo erupted approximately 25,000 years ago, and then landed somewhere else.
To find out, the team set out on an expedition to collect soil samples from islands in the vicinity of North Island, digging down to where ash from the eruption could be found. They took the samples (as well as soil from above and below the ash) back to their lab and studied them under a microscope and found that their hunch had been right. One of the species of diatoms found in the ash matched nearly perfectly with samples taken from the lake bottom on North Island (but not with samples found in the soil above and below the ash). That means when Taupo erupted beneath Lake Huka, it sent a stream of moisture along with ash into the atmosphere which subsequently landed in the sea and on the surface of islands nearby. The researchers found that diatoms that had been carried by the moisture could be found as far away as 525 miles away, suggesting that volcanic eruptions should now be listed as a source for diatomic dispersal.
The researchers don’t believe the diatoms could have survived such a harrowing journey, but their spores very likely could have. That means, they say, that other eruptions that have occurred beneath lakes or other bodies of water could have sent diatom spores hundreds or even thousands of miles away, allowing them to grow in new places.
More info: High-flying diatoms: Widespread dispersal of microorganisms in an explosive volcanic eruption, Geology, First published online September 6, 2013, DOI: 10.1130/G34829.1
Understanding the evolution of flight with a micro raptor in the wind tunnel at the University of Southampton. (Credit: Image courtesy of University of Southampton)
A study into the aerodynamic performance of feathered dinosaurs, by scientists from the University of Southampton, has provided new insight into the evolution of bird flight.
In recent years, new fossil discoveries have changed our view of the early evolution of birds and, more critically, their powers of flight. We now know about a number of small-bodied dinosaurs that had feathers on their wings as well as on their legs and tails: completely unique in the fossil record..
However, even in light of new fossil discoveries, there has been a huge debate about how these dinosaurs were able to fly.
Scientists from the University of Southampton hope to have ended this debate by examining the flight performance of one feathered dinosaur pivotal to this debate — the early Cretaceous five-winged paravian Microraptor. The first theropod described with feathers on its arms, legs and tail (five potential lifting surfaces), Microraptor implies that forelimb-dominated bird flight passed through a four-wing (‘tetrapteryx’) phase and represents an important stage in the evolution of gliding and flapping.
The Southampton researchers performed a series of wind tunnel experiments and flight simulations on a full-scale, anatomically accurate model of Microraptor.
Results of the team’s wind tunnel tests show that Microraptor would have been most stable gliding when generating large amounts of lift with its wings.. Flight simulations demonstrate that this behaviour had advantages since this high lift coefficient allows for slow glides, which can be achieved with less height loss. For gliding down from low elevations, such as trees, this slow, and aerodynamically less efficient flight was the gliding strategy that results in minimal height loss and longest glide distance.
Much debate, centred on the position and orientation of Microraptor’s legs and wing shape turns out to be irrelevant — tests show that changes in these variables make little difference to the dinosaur’s flight.
Dr Gareth Dyke, Senior Lecturer in Vertebrate Palaeontology at the University of Southampton and co-author of the study, says: “Significant to the evolution of flight, we show that Microraptor did not require a sophisticated, ‘modern’ wing morphology to undertake effective glides, as the high-lift coefficient regime is less dependent upon detail of wing morphology.”
“This is consistent with the fossil record, and also with the hypothesis that symmetric ‘flight’ feathers first evolved in dinosaurs for non-aerodynamic functions, later being adapted to form aerodynamically capable surfaces.”
Dr Roeland de Kat, Research Fellow in the Aerodynamics and Flight Mechanics Research Group at the University of Southampton and co-author of the study, says: “What interests me is that aerodynamic efficiency is not the dominant factor in determining Microraptor’s glide efficiency. However, it needs a combination of a high lift coefficient and aerodynamic efficiency to perform at its best.”
The paper ‘Aerodynamic performance of the feathered dinosaur Microraptor and the evolution of feathered flight’ is published in the latest issue of Nature Communications.
Dr Dyke and fellow Southampton palaeontologists will showcase their ground-breaking research at the Celebrating Dinosaur Island: Jehol-Wealden International Conference on 21 and 22 September.
The Isle of Wight (Dinosaur Island) and China are key areas for Cretaceous fossils, especially dinosaurs. To celebrate this connection, Chinese and UK dinosaur palaeontologists will discuss their research at the National Oceanography Centre, Southampton and visit key dinosaur sites on the Isle of Wight and network with tourism and business leaders to build connections for future palaentological research.
Video :
Note : The above story is based on materials provided by University of Southampton.
This image shows olivine crystal of a sample used to simulate deep earthquakes. The olivine contains small crystals of pyroxene within it that have been cut by “nanofaults.” The numbers each show the parts of a pyroxene crystal that has been cut and displaced along a “nanofault.” (Credit: Green Lab, UC Riverside.)
More than 20 years ago, geologist Harry Green, now a distinguished professor of the graduate division at the University of California, Riverside, and colleagues discovered a high-pressure failure mechanism that they proposed then was the long-sought mechanism of very deep earthquakes (earthquakes occurring at more than 400 km depth).
The result was controversial because seismologists could not find a seismic signal in Earth that could confirm the results.
Seismologists have now found the critical evidence. Indeed, beneath Japan, they have even imaged the tell-tale evidence and showed that it coincides with the locations of deep earthquakes.
In the Sept. 20 issue of the journal Science, Green and colleagues show just how such deep earthquakes can be simulated in the laboratory.
“We confirmed essentially all aspects of our earlier experimental work and extended the conditions to significantly higher pressure,” Green said. “What is crucial, however, is that these experiments are accomplished in a new type of apparatus that allows us to view and analyze specimens using synchrotron X-rays in the premier laboratory in the world for this kind of experiments — the Advanced Photon Source at Argonne National Laboratory.”
The ability to do such experiments has now allowed scientists like Green to simulate the appropriate conditions within Earth and record and analyze the “earthquakes” in their small samples in real time, thus providing the strongest evidence yet that this is the mechanism by which earthquakes happen at hundreds of kilometers depth.
The origin of deep earthquakes fundamentally differs from that of shallow earthquakes (earthquakes occurring at less than 50 km depth). In the case of shallow earthquakes, theories of rock fracture rely on the properties of coalescing cracks and friction.
“But as pressure and temperature increase with depth, intracrystalline plasticity dominates the deformation regime so that rocks yield by creep or flow rather than by the kind of brittle fracturing we see at smaller depths,” Green explained. “Moreover, at depths of more than 400 kilometers, the mineral olivine is no longer stable and undergoes a transformation resulting in spinel. a mineral of higher density”
The research team focused on the role that phase transformations of olivine might play in triggering deep earthquakes. They performed laboratory deformation experiments on olivine at high pressure and found the “earthquakes” only within a narrow temperature range that simulates conditions where the real earthquakes occur in Earth.
“Using synchrotron X-rays to aid our observations, we found that fractures nucleate at the onset of the olivine to spinel transition,” Green said. “Further, these fractures propagate dynamically so that intense acoustic emissions are generated. These phase transitions in olivine, we argue in our research paper, provide an attractive mechanism for how very deep earthquakes take place.”
Green was joined in the study by Alexandre Schubnel at the Ecole Normale Supérieure, France; Fabrice Brunet at the Université de Grenoble, France; and Nadège Hilairet, Julian Gasc and Yanbin Wang at the University of Chicago, Ill.
Note : The above story is based on materials provided by University of California – Riverside. The original article was written by Iqbal Pittalwala.
The May 24, 2013 Mw 8.3 earthquake beneath the Sea of Okhotsk, Russia, occurred as a result of normal faulting at a depth of approximately 600 km (portion of USGS poster). (Credit: U.S. Geological Survey)
A magnitude 8.3 earthquake that struck deep beneath the Sea of Okhotsk on May 24, 2013, has left seismologists struggling to explain how it happened. At a depth of about 609 kilometers (378 miles), the intense pressure on the fault should inhibit the kind of rupture that took place.
“It’s a mystery how these earthquakes happen. How can rock slide against rock so fast while squeezed by the pressure from 610 kilometers of overlying rock?” said Thorne Lay, professor of Earth and planetary sciences at the University of California, Santa Cruz.
Lay is coauthor of a paper, published in the September 20 issue of Science, analyzing the seismic waves from the Sea of Okhotsk earthquake. First author Lingling Ye, a graduate student working with Lay at UC Santa Cruz, led the seismic analysis, which revealed that this was the largest deep earthquake ever recorded, with a seismic moment 30 percent larger than that of the next largest, a 1994 earthquake 637 kilometers beneath Bolivia.
Deep earthquakes occur in the transition zone between the upper mantle and lower mantle, from 400 to 700 kilometers below the surface. They result from stress in a deep subducted slab where one plate of Earth’s crust dives beneath another plate. Such deep earthquakes usually don’t cause enough shaking on the surface to be hazardous, but scientifically they are of great interest.
The energy released by the Sea of Okhotsk earthquake produced vibrations recorded by several thousand seismic stations around the world. Ye, Lay, and their coauthors determined that it released three times as much energy as the 1994 Bolivia earthquake, comparable to a 35 megaton TNT explosion. The rupture area and rupture velocity were also much larger. The rupture extended about 180 kilometers, by far the longest rupture for any deep earthquake recorded, Lay said. It involved shear faulting with a fast rupture velocity of about 4 kilometers per second (about 9,000 miles per hour), more like a conventional earthquake near the surface than other deep earthquakes. The fault slipped as much as 10 meters, with average slip of about 2 meters.
“It looks very similar to a shallow event, whereas the Bolivia earthquake ruptured very slowly and appears to have involved a different type of faulting, with deformation rather than rapid breaking and slippage of the rock,” Lay said.
The researchers attributed the dramatic differences between these two deep earthquakes to differences in the age and temperature of the subducted slab. The subducted Pacific plate beneath the Sea of Okhotsk (located between the Kamchatka Peninsula and the Russian mainland) is a lot colder than the subducted slab where the 1994 Bolivia earthquake occurred.
“In the Bolivia event, the warmer slab resulted in a more ductile process with more deformation of the rock,” Lay said.
The Sea of Okhotsk earthquake may have involved re-rupture of a fault in the plate produced when the oceanic plate bent down into the Kuril-Kamchatka subduction zone as it began to sink. But the precise mechanism for initiating shear fracture under huge confining pressure remains unclear. The presence of fluid can lubricate the fault, but all of the fluids should have been squeezed out of the slab before it reached that depth.
“If the fault slips just a little, the friction could melt the rock and that could provide the fluid, so you would get a runaway thermal effect. But you still have to get it to start sliding,” Lay said. “Some transformation of mineral forms might give the initial kick, but we can’t directly detect that. We can only say that it looks a lot like a shallow event.”
Note : The above story is based on materials provided by University of California – Santa Cruz. The original article was written by Tim Stephens.
A true-color NASA satellite mosaic of Earth. (Credit: NASA)
Habitable conditions on Earth will be possible for at least another 1.75 billion years – according to astrobiologists at the University of East Anglia.
Findings published today in the journal Astrobiology reveal the habitable lifetime of planet Earth – based on our distance from the sun and temperatures at which it is possible for the planet to have liquid water.
The research team looked to the stars for inspiration. Using recently discovered planets outside our solar system (exoplanets) as examples, they investigated the potential for these planets to host life.
The research was led by Andrew Rushby, from UEA’s school of Environmental Sciences. He said: “We used the ‘habitable zone’ concept to make these estimates – this is the distance from a planet’s star at which temperatures are conducive to having liquid water on the surface.”
“We used stellar evolution models to estimate the end of a planet’s habitable lifetime by determining when it will no longer be in the habitable zone. We estimate that Earth will cease to be habitable somewhere between 1.75 and 3.25 billion years from now. After this point, Earth will be in the ‘hot zone’ of the sun, with temperatures so high that the seas would evaporate. We would see a catastrophic and terminal extinction event for all life.
“Of course conditions for humans and other complex life will become impossible much sooner – and this is being accelerated by anthropogenic climate change. Humans would be in trouble with even a small increase in temperature, and near the end only microbes in niche environments would be able to endure the heat.
“Looking back a similar amount of time, we know that there was cellular life on earth. We had insects 400 million years ago, dinosaurs 300 million years ago and flowering plants 130 million years ago. Anatomically modern humans have only been around for the last 200,000 years – so you can see it takes a really long time for intelligent life to develop.
“The amount of habitable time on a planet is very important because it tells us about the potential for the evolution of complex life – which is likely to require a longer period of habitable conditions.
“Looking at habitability metrics is useful because it allows us to investigate the potential for other planets to host life, and understand the stage that life may be at elsewhere in the galaxy.
“Of course, much of evolution is down to luck, so this isn’t concrete, but we know that complex, intelligent species like humans could not emerge after only a few million years because it took us 75 per cent of the entire habitable lifetime of this planet to evolve. We think it will probably be a similar story elsewhere.”
Almost 1,000 planets outside our solar system have been identified by astronomers. The research team looked at some of these as examples, and studied the evolving nature of planetary habitability over astronomical and geological time.
“Interestingly, not many other predictions based on the habitable zone alone were available, which is why we decided to work on a method for this. Other scientists have used complex models to make estimates for the Earth alone, but these are not suitable for applying to other planets.
“We compared Earth to eight planets which are currently in their habitable phase, including Mars. We found that planets orbiting smaller mass stars tend to have longer habitable zone lifetimes.
“One of the planets that we applied our model to is Kepler 22b, which has a habitable lifetime of 4.3 to 6.1 billion years. Even more surprising is Gliese 581d which has a massive habitable lifetime of between 42.4 to 54.7 billion years. This planet may be warm and pleasant for 10 times the entire time that our solar system has existed!
“To date, no true Earth analogue planet has been detected. But it is possible that there will be a habitable, Earth-like planet within 10 light-years, which is very close in astronomical terms. However reaching it would take hundreds of thousands of years with our current technology.
“If we ever needed to move to another planet, Mars is probably our best bet. It’s very close and will remain in the habitable zone until the end of the Sun’s lifetime — six billion years from now.”
Anomalocaris “arm” from the Mt. Stephen Trilobite Beds, Middle Cambrian, near Field, British Columbia, Canada. (Credit: By Wilson44691 (Own work) [Public domain], via Wikimedia Commons)The explosion of animal life on Earth around 520 million years ago was the result of a combination of interlinked factors rather than a single underlying cause, according to a new study.
Dozens of individual theories have been put forward over the past few decades for this rapid diversification of animal species in the early Cambrian period of geological time.
But a paper by Professor Paul Smith of Oxford University and Professor David Harper of Durham University suggests a more holistic approach is required to discover the reasons behind what has become known as the Cambrian Explosion.
Theories for the Cambrian Explosion fall into three main categories — geological, geochemical and biological — and most have been claimed as standalone processes that were the main cause of the explosion.
Whatever the cause, this major evolutionary event led to a wide range of biological innovation, including the origin of modern ecosystems, a rapid increase in animal diversity, the origin of skeletons and the first appearance of specialist modes of life such as burrowing and swimming.
Among the weird and wonderful creatures to emerge in the early Cambrian was Anomalocaris, the free-swimming, metre-long top predator of the time with a mouth composed of 32 overlapping plates that could constrict to crush prey. It is distantly related to modern arthropods, including crabs and lobsters.
Vertebrate animals also made their first appearance in the Cambrian Explosion, the distant ancestors of modern fish, reptiles, birds and mammals.
Professor Smith, Professor Harper and a team of scientists have spent four years working on data from a site in northernmost Greenland, facing the Arctic Ocean.
The site, at Siriuspasset, is located at 83°N, just 500 miles from the North Pole in a remote part of north Greenland. Although logistically very difficult to reach, Siriuspasset attracted the team because of the high quality of its fossil material and the insights it provides.
Professor Smith and Professor Harper’s findings are published in the latest edition of the journal Science.
Professor Smith, lead author of the report and Director of the Oxford University Museum of Natural History, said: ‘This is a period of time that has attracted a lot of attention because it is when animals appear very abruptly in the fossil record, and in great diversity. Out of this event came nearly all of the major groups of animals that we recognise today.
“Because it is such a major biological event, it has attracted much opinion and speculation about its cause.”
Described by the researchers as a ‘cascade of events’, the interacting causes behind the explosion in animal life are likely to have begun with an early Cambrian sea level rise. This generated a large increase in the area of habitable seafloor, which in turn drove an increase in animal diversity. These early events then translate into the complex interaction of biological, geochemical and geological processes described in individual hypotheses.
Professor Harper, Professor of Palaeontology in the Department of Earth Sciences at Durham University, said: “The Cambrian Explosion is one of the most important events in the history of life on our planet, establishing animals as the most visible part of the planet’s marine ecosystems.
“It would be naïve to think that any one cause ignited this phenomenal explosion of animal life. Rather, a chain reaction involving a number of biological and geological drivers kicked into gear, escalating the planet’s diversity during a relatively short interval of deep time.
“The Cambrian Explosion set the scene for much of the subsequent marine life that built on cascading and nested feedback loops, linking the organisms and their environment, that first developed some 520 million years ago.”
Professor Smith said: “Work at the Siriuspasset site in north Greenland has cemented our thinking that it wasn’t a matter of saying one hypothesis is right and one is wrong. Rather than focusing on one single cause, we should be looking at the interaction of a number of different mechanisms.
“Most of the hypotheses have at least a kernel of truth, but each is insufficient to have been the single cause of the Cambrian explosion. What we need to do now is focus on the sequence of interconnected events and the way they related to each other — the initial geological triggers that led to the geochemical effects, followed by a range of biological processes.”
The research was funded by the Agouron Institute, the Carlsberg Foundation and Geocenter Danmark.
Note : The above story is based on materials provided by University of Oxford, via EurekAlert!, a service of AAAS.
Scientists at the University of Leeds have solved a 300-year-old riddle about which direction the centre of Earth spins.
Earth’s inner core, made up of solid iron, ‘superrotates’ in an eastward direction — meaning it spins faster than the rest of the planet — while the outer core, comprising mainly molten iron, spins westwards at a slower pace.
Although Edmund Halley — who also discovered the famous comet — showed the westward-drifting motion of Earth’s geomagnetic field in 1692, it is the first time that scientists have been able to link the way the inner core spins to the behavior of the outer core. The planet behaves in this way because it is responding to Earth’s geomagnetic field.
The findings, published today in Proceedings of the National Academy of Sciences, help scientists to interpret the dynamics of the core of Earth, the source of our planet’s magnetic field.
In the last few decades, seismometers measuring earthquakes travelling through Earth’s core have identified an eastwards, or superrotation of the solid inner core, relative to Earth’s surface.
“The link is simply explained in terms of equal and opposite action,” explains Dr Philip Livermore, of the School of Earth and Environment at the University of Leeds. “The magnetic field pushes eastwards on the inner core, causing it to spin faster than Earth, but it also pushes in the opposite direction in the liquid outer core, which creates a westward motion.”
The solid iron inner core is about the size of the Moon. It is surrounded by the liquid outer core, an iron alloy, whose convection-driven movement generates the geomagnetic field.
The fact that Earth’s internal magnetic field changes slowly, over a timescale of decades, means that the electromagnetic force responsible for pushing the inner and outer cores will itself change over time. This may explain fluctuations in the predominantly eastwards rotation of the inner core, a phenomenon reported for the last 50 years by Tkalčić et al. in a recent study published in Nature Geoscience.
Other previous research based on archeological artefacts and rocks, with ages of hundreds to thousands of years, suggests that the drift direction has not always been westwards: some periods of eastwards motion may have occurred in the last 3,000 years. Viewed within the conclusions of the new model, this suggests that the inner core may have undergone a westwards rotation in such periods.
The authors used a model of Earth’s core which was run on the giant super-computer Monte Rosa, part of the Swiss National Supercomputing Centre in Lugano, Switzerland. Using a new method, they were able to simulate Earth’s core with an accuracy about 100 times better than other models.
Note : The above story is based on materials provided by University of Leeds, via EurekAlert!, a service of AAAS.
University of Calgary Geoscience professor David Eaton has published a paper that provides new insights into the birth of continents.
New research led by a University of Calgary geophysicist provides strong evidence against continent formation above a hot mantle plume, similar to an environment that presently exists beneath the Hawaiian Islands.
The analysis, published this month in Nature Geoscience, indicates that the nuclei of Earth’s continents formed as a byproduct of mountain-building processes, by stacking up slabs of relatively cold oceanic crust. This process created thick, strong ‘keels’ in Earth’s mantle that supported the overlying crust and enabled continents to form.
The scientific clues leading to this conclusion derived from computer simulations of the slow cooling process of continents, combined with analysis of the distribution of diamonds in the deep Earth.
The Department of Geoscience’s Professor David Eaton developed computer software to enable numerical simulation of the slow diffusive cooling of Earth’s mantle over a time span of billions of years.
Working in collaboration with former graduate student, Assistant Professor Claire Perry from the Universite du Quebec a Montreal, Eaton relied on the geological record of diamonds found in Africa to validate his innovative computer simulations.
“For the first time, we are able to quantify the thermal evolution of a realistic 3D Earth model spanning billions of years from the time continents were formed,” states Perry.
Mantle plumes consist of an upwelling of hot material within Earth’s mantle. Plumes are thought to be the cause of some volcanic centres, especially those that form a linear volcanic chain like Hawaii. Diamonds, which are generally limited to the deepest and oldest parts of the continental mantle, provide a wealth of information on how the host mantle region may have formed.
“Ancient mantle keels are relatively strong, cold and sometimes diamond-bearing material. They are known to extend to depths of 200 kilometres or more beneath the ancient core regions of continents,” explains Professor David Eaton. “These mantle keels resisted tectonic recycling into the deep mantle, allowing the preservation of continents over geological time and providing suitable environments for the development of the terrestrial biosphere.”
His method takes into account important factors such as dwindling contribution of natural radioactivity to the heat budget, and allows for the calculation of other properties that strongly influence mantle evolution, such as bulk density and rheology (mechanical strength).
“Our computer model emerged from a multi-disciplinary approach combining classical physics, mathematics and computer science,” explains Eaton. “By combining those disciplines, we were able to tackle a fundamental geoscientific problem, which may open new doors for future research.”
This work provides significant new scientific insights into the formation and evolution of continents on Earth.
Columnar Oligocene flood basalt sheets cover the Eocene Bahariya Formation at Gebel Mandisha area in the Bahariya oasis depression.
The Mandisha basalts are located with the position of 28° 54′ E and 28°22′ N, nearby the iron ore mines in the eastern direction. The basaltic intrusions took place during Oligocene, when the Gulf of Suez rift began to open.
Mandisha basalt outcrops
As noted earlier, hydrovolcanic solutions associated with this subvolcanic activity caused intensivemineralization and iron precipitation in parts of the depression. Iron forms as a replacement to Eocene limestone where open cast quarries are located in several places. Mostly known are the mines of El Harra area and El Gedida area at the northern edge of the depression (Hussein and Sharkawi, 1990).
New research from Carnegie on methane under pressure will help scientists understand the chemistry of planetary interiors, including Neptune and and Uranus, as well as hydrocarbon energy resources and diamond formation here on Earth.Credit: Courtesy of Alexander Goncharov, Carnegie Institution for Science.
Washington, D.C.—Hydrocarbons from the Earth make up the oil and gas that heat our homes and fuel our cars. The study of the various phases of molecules formed from carbon and hydrogen under high pressures and temperatures, like those found in the Earth’s interior, helps scientists understand the chemical processes occurring deep within planets, including Earth.
New research from a team led by Carnegie’s Alexander Goncharov hones in on the hydrocarbon methane (CH4), which is one of the most abundant molecules in the universe. Despite its ubiquity, methane’s behavior under the conditions found in planetary interiors is poorly understood due to contradictory information from various modeling studies. The work is published by Nature Communications.
Lead author Sergey Lobanov explains: “Our knowledge of physics and chemistry of volatiles inside planets is based mainly on observations of the fluxes at their surfaces. High-pressure, high-temperature experiments, which simulate conditions deep inside planets and provide detailed information about the physical state, chemical reactivity, and properties of the planetary materials, remain a big challenge for us.”
For example, methane’s melting behavior is known only below 70,000 times normal atmospheric pressure (7 GPa). The ability to observe it under much more extreme conditions is fundamental information for planetary models.
Moreover, its reactivity under extreme conditions also needs to be understood. Previous studies indicated little information about methane’s chemical reactivity under pressure and temperature conditions similar to those found in the deep Earth. This led to the assumption that methane is the main hydrocarbon phase of carbon, oxygen, and hydrogen-containing fluid in some parts of the Earth’s mantle. But the team’s work shows that it is necessary to question this assumption.
Using high-pressure experimental techniques, the team–including Carnegie’s Lobanov, Xiao-Jia Chen, Chang-Sheng Zha, and Ho-Kwang “Dave” Mao–was able to examine methane’s phases and reactivity under a range of temperatures and pressures mimicking environments found beneath Earth’s surface.
At pressures reaching 790,000 times normal atmospheric pressure (80 GPa), methane’s melting temperature is still below 1,900 degrees Fahrenheit. This suggests that methane is not a solid under any conditions met deep within most planets. What’s more, its melting point is even lower than melting temperatures of water (H2O) and ammonia (NH3), other very important components in the interiors of giant planets.
As the temperature increases above about 1,700 degrees Fahrenheit, methane becomes more chemically reactive. First, it partly disassociates into elemental carbon and hydrogen. Then, with further temperature increases, light hydrocarbon molecules start to form. Pressure also affects the composition of the carbon-hydrogen system, with heavy hydrocarbons becoming apparent at pressures above 250,000 times atmospheric pressure (25 GPa), indicating that under deep mantle conditions the environment is likely methane poor.
These findings have implications both for Earth’s deep chemistry and for the geochemistry of icy gas giant planets such as Uranus and Neptune. The team argues that this reactivity may play a role in the formation of ultradeep diamonds deep within the mantle. They assert that their findings should be taken into account in future models of the interiors of Neptune and Uranus, which are believed to have mantles consisting of a mixture of methane, water, and ammonia components.
Note : The above story is based on materials provided by Carnegie Institution
Scientists have confirmed that Saturn’s largest moon, here circling the gas giant, is home to intriguing organic chemical evolution. (Credit: NASA/JPL-Caltech/SSI)
Glimpses of the events that nurtured life on Earth more than 3.5 billion years ago are coming from an unlikely venue almost 1 billion miles away, according to the leader of an effort to understand Titan, one of the most unusual moons in the solar system.
In a talk in Indianapolis on September 12 at the 246th National Meeting & Exposition of the American Chemical Society (ACS), Jonathan Lunine, Ph.D., said that Titan, the largest of Saturn’s several dozen moons, is providing insights into the evolution of life unavailable elsewhere.
“Data sent back to Earth from space missions allow us to test an idea that underpins modern science’s portrait of the origin of life on Earth,” Lunine said. “We think that simple organic chemicals present on the primordial Earth, influenced by sunlight and other sources of energy, underwent reactions that produced more and more complex chemicals. At some point, they crossed a threshold — developing the ability to reproduce themselves. Could we test this theory in the lab? These processes have been underway on Titan for billions of years. We don’t have a billion years in the lab. We don’t even have a thousand years.”
Lunine, who is with Cornell University and is one of about 260 scientists involved with the Cassini-Huygens mission, explained that only two celestial objects in the solar system have the large amounts of organic substances on their surfaces to provide such information. They are Titan and Earth. Organic substances on Earth, however, have been cycled through living things countless times. Titan’s organic materials, which include deposits of methane and other hydrocarbons as large as some of the Great Lakes, are in pristine condition — never, so far as anyone knows, in contact with life.
Titan is the only moon in the solar system known to have an atmosphere. Like Earth, most of it consists of nitrogen, with methane the second-most abundant. Sunlight strikes Titan’s upper atmosphere, breaking that compound into pieces that react with each other and nitrogen to form organic compounds. Those include ethane, acetylene, hydrogen cyanide, cyanoacetylene and others — all familiar terrestrial chemicals.
“We’ve got a very good inventory of what’s there in the atmosphere,” Lunine said. “What we’ve only recently begun to understand is the fate of these organics at the surface of Titan.”
Lunine explained that for a long time, Mars had captured the public’s and scientists’ imagination as a possible location to find interesting organic chemistry and hints at life outside Earth — and for good reason: It is an Earth-like planet relatively close to the Sun. But scientists have only found simple organic materials on the red planet.
Recent research has provided fascinating hints that liquid water may exist deep under Titan’s surface. Other data suggest that areas of Titan’s seafloor may be similar to areas of Earth’s seafloors where hydrothermal vents exist. These passways into Earth’s interior spout hot, mineral-rich water that fosters an array of once-unknown forms of life. Lunine also cited research that has identified prime potential landing spots on Titan should the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA) or other space agencies decide on another mission to Titan.
Scientists now know, thanks to the joint NASA-ESA spacecraft that arrived at Saturn in 2004 after a seven-year journey through the solar system, that Titan shares a surprising number of features with Earth. The enormous volumes of data that Cassini’s 12 scientific instruments and the Huygens surface probe streamed back to Earth paint a complex picture of Titan’s surface and the dense atmosphere that enshrouds it. Rivers flow into lakes. Wind sweeps across dunes. Giant storms brew, and clouds float across the hazy sky.
The catch is that Titan, nearly a billion miles from the Sun and a little larger than Earth’s own moon, is mostly frozen. It only receives about 1 percent of the sunlight that Earth gets. As a result, it is unimaginably frigid. At minus 290 degrees Fahrenheit — that’s 160 degrees colder than the coldest recorded temperature in Antarctica — its water ice is rock solid, at least on the surface. And the rivers and lakes? They are made of liquid hydrocarbons, ethane and methane, which on balmy Earth are the main components of natural gas. Titan’s deposits may be 10-100 times greater than all of Earth’s oil and gas reserves, estimates suggest.
Lunine acknowledged funding from the Cassini Project, the NASA Astrobiology Institute and the John Templeton Foundation.
Note : The above story is based on materials provided by American Chemical Society (ACS).
Rare dinosaur remains could be forever lost to the scientific community when they go under the hammer in November.
The remarkably preserved fossils of two “duelling” dinosaurs frozen in a death clinch could fetch up to $10m.
But scientists want the opportunity to examine the specimens of the tyrannosaur, which appears to have bitten off more than it could chew.
Details of the discovery, from Montana, US, were discussed at the British Science Festival in Newcastle.
The large arms and thin head of this most complete tyrannosaur ever discovered suggest it is a new species, called Nanotyrannus, living alongside and related to T. rex.
The observations were made by Dr Phil Manning of Manchester University.
Some 65 to 67 million years ago, in an area that now lies the middle of Montana, T. rex was the top predator of the ecosystem. Dr Manning has just returned from an excavation of a new T. rex skeleton that he is preparing for a museum in Leiden, Germany.
Fossil fragments of T. rex are found throughout the rocks called the “Hell Creek Formation” in Montana, but never before has an entire tyrannosaur skeleton been found.
Only two T. rex skeletons that are more than half complete have been ever been recovered. The Fields Museum in Chicago has the most complete T. rex, at 85% of a skeleton, which was bought at auction for a record sum, and the Black Hills Museum in South Dakota has a 65% complete T. rex.
Death clinch
There has been great excitement, therefore, over the recent excavation of an entire and complete tyrannosaur predator from the Hell Creek Formation. More than that, it was found forever frozen in a linked death clasp with its prey, a complete Triceratops.
Dr Phil Manning from the University of Manchester explained at the British Science Festival in Newcastle how new observations show a tooth from the tyrannosaur embedded between the neck vertebrae of the Triceratops, while the skull of the tyrannosaur appears to have been shattered by a blow from the Triceratops.
“It was a bad day for both of them” quipped Dr Manning. “These animals could have been fighting on the banks of a river. They both became mortally injured.” They were then rapidly buried and preserved as fossils.
But there is more to this remarkable death duelling pair than the preservation of their last moments as entire skeletons. The preservation also solves a longstanding scientific question.
Long-armed tyrannosaur
In 1988, a similar skull bone from a predatory dinosaur was identified as a distinct species, which was then named Nanotyrannus, but the identification from one skull fossil was not widely accepted, with many suggesting that this was simply a young T. rex.
The dispute over whether a second large predator lived alongside T. Rex has rumbled on over the last decades, but Dr Manning’s observations of the new entire skeleton help resolve the issue.
Nanotyrannus lived alongside T. rex, but had its own ecological niche
T. rex has some notable distinctive features, one of which is its very small arms. Dr Phil Manning has just returned from a visit to inspect the new specimen from Montana, and described its very large fore arms. Despite being about half the body size of an adult T. rex the arms of Nanotyrannus are noticeably larger than those of T. rex.
Nanotyrannus is characterised by Dr Manning as having its own ecological niche, with a long swan-like neck, relatively large fore arms, and a narrower gracile skull. “If you think of the savannah of Africa today, the lion is taking down the big prey and the cheetah is maybe taking down the small prey. Maybe we are looking at the cheetah of the Cretaceous here: we’ve got similar niche partitioning of the ecosystem that existed 65 to 67 million years ago”.
“When you have a big predator, like T. rex, it means that you have a healthy established ecosystem. So it’s not surprising to find a more complex system in place at the end of the Cretaceous” Dr Manning explained.
Dr David Norman of the University of Cambridge was not involved in the study. He commented to the BBC “A really nice skull has been described previously, and looks rather low and long compared to a classic T. rex skull, which led to the suggestion of Nanotyrannus.
“If this new specimen has larger forelimbs and a gracile skull on a more slender swan-like neck, it provides plausible reasons to substantiate the idea that this is a new genus.”
Forever lost?
The remarkable specimen was discovered on private land by an independent fossil collector, and is now being offered for sale by auction. It is expected to fetch as much as $10m dollars when it goes under the hammer in November.
The scientific community demands that original research material like this sample be deposited in accessible museum collections if the description or discoveries of new species or genus are to be accepted, to allow observations to be verified and studied openly by others.
The auction of the Nanotyrannus – Triceratops pair may yet stymie the acceptance of Nanotyrannus as a new species. If it goes to a private collection it will no longer be available to science, and the unique observations made thus far will never be subject to peer-scrutiny.
The whole issue of the commercialisation of fossil discovery is raising concerns among palaeontologists and other scientists, and may hinder future discovery, they say.
Discussing the issue, Dr Norman commented: “This is the most distasteful part of it. Ever since the T. rex was sold to the Fields Museum in Chicago for $8m, the commercial value of fossils has been hyped.
“This spiralling effect means that more and more scientifically important objects risk being removed from the community for scientific study. They fall into private hands because they become objects d’art.
“It destroys the whole ethos of the availability of specimens. These fossils were left by Nature, shouldn’t they be available to be appreciated and studied by everybody, rather than falling into private hands?
“There are national issues about how fossils are sold and valued that vary from country to country. It is becoming a minefield now that fossils can have a high value, and makes it a curatorial nightmare for museums.”
Note : The above story is based on materials provided by BBC News , By Simon Redfern
A sample of jaws from the Mesozoic crocodile fossil record. From top to bottom jaws are from: Kaprosuchus (Cretaceous) (image by Carol Abraczinskas), Simosuchus (Cretaceous), Mariliasuchus (Cretaceous) (courtesy of The American Museum of Natural History), Dakosaurus (Jurassic to Cretaceous) and Cricosaurus (Jurassic to Cretaceous) (courtesy of Jeremías Taborda). (Credit: Image courtesy of University of Bristol)
New research has revealed the hidden past of crocodiles, showing for the first time how these fierce reptiles evolved and survived in a dinosaur dominated world.
While most modern crocodiles live in freshwater habitats and feed on mammals and fish, their ancient relatives were extremely diverse — with some built for running around like dogs on land and others adapting to life in the open ocean, imitating the feeding behaviour of today’s killer whales.
Research published today [11 September] in the journal Proceedings of the Royal Society B shows, for the first time, how the jaws of ancient crocodiles evolved to enable these animals to survive in vastly different environments, all whilst living alongside the dinosaurs 235 to 65 million years ago.
The study was conducted by Tom Stubbs and Dr Emily Rayfield from the University of Bristol, together with Dr Stephanie Pierce from The Royal Veterinary College and Dr Phil Anderson from Duke University.
Tom Stubbs, who led the research at the University of Bristol, said: “The ancestors of today’s crocodiles have a fascinating history that is relatively unknown compared to their dinosaur counterparts. They were very different creatures to the ones we are familiar with today, much more diverse and, as this research shows, their ability to adapt was quite remarkable.
“Their evolution and anatomical variation during the Mesozoic Era was exceptional. They evolved lifestyles and feeding ecologies unlike anything seen today.”
The research team examined variation in the morphology (shape) and biomechanics (function) of the lower jaws in over 100 ancient crocodiles, using a unique combination of numerical methods.
Dr Stephanie Pierce, from The Royal Veterinary College, said: “We were curious how extinction events and adaptations to extreme environments during the Mesozoic — a period covering over 170 million years — impacted the feeding systems of ancient crocodiles and to do this we focused our efforts on the main food processing bone, the lower jaw.”
By analysing variation in the lower jaw, the researchers provide novel insights into how the feeding systems of ancient crocodiles evolved as the group recovered from the devastating end-Triassic extinction event and subsequently responded to the distribution of ecological resources, such as habitat and foodstuff.
For the first time, the research has shown that, following the end-Triassic extinction, ancient crocodiles invaded the Jurassic seas and evolved jaws built primarily for hydrodynamic efficiency to capture agile prey, such as fish. However, only a small range of elongate lower jaw shapes were suitable in Jurassic marine environments.
The study has also revealed that variation peaked again in the Cretaceous, where ancient crocodiles evolved a great variety of lower jaw shapes, as they adapted to a diverse range of feeding ecologies and terrestrial environments, alongside the dinosaurs.
Surprisingly, the lower jaws of Cretaceous crocodiles did not have a great amount of biomechanical variation and, instead, the fossil record points towards novel adaptations in other areas of their anatomy, such as armadillo-like body armour.
Dr Pierce added: “Our results show that the ability to exploit a variety of different food resources and habitats, by evolving many different jaw shapes, was crucial to recovering from the end-Triassic extinction and most likely contributed to the success of Mesozoic crocodiles living in the shadow of the dinosaurs.”
This exceptional variation has never before been explored numerically, with no studies ever having incorporated such a wide range of crocodiles over such a long time period.
Note : The above story is based on materials provided by University of Bristol, via EurekAlert!, a service of AAAS.
A portion of the asteroidal Sutter’s Mill meteorite used in this study. (Credit: Image courtesy of Arizona State University)
An important discovery has been made concerning the possible inventory of molecules available to the early Earth. Scientists led by Sandra Pizzarello, a research professor in ASU’s Department of Chemistry and Biochemistry, found that the Sutter’s Mill meteorite, which exploded in a blazing fireball over California last year, contains organic molecules not previously found in any meteorites. These findings suggest a far greater availability of extraterrestrial organic molecules than previously thought possible, an inventory that could indeed have been important in molecular evolution and life itself.
The work is being published in this week’s Proceedings of the National Academy of Sciences. The paper is titled “Processing of meteoritic organic materials as a possible analog of early molecular evolution in planetary environments,” and is co-authored by Pizzarello, geologist Lynda Williams, NMR specialist Gregory Holland and graduate student Stephen Davidowski, all from ASU.
Coincidentally, Sutter’s Mill is also the gold discovery site that led to the 1849 California Gold Rush. Detection of the falling meteor by Doppler weather radar allowed for rapid recovery so that scientists could study for the first time a primitive meteorite with little exposure to the elements, providing the most pristine look yet at the surface of primitive asteroids.
“The analyses of meteorites never cease to surprise you … and make you wonder,” explains Pizzarello. “This is a meteorite whose organics had been found altered by heat and of little appeal for bio- or prebiotic chemistry, yet the very Solar System processes that lead to its alteration seem also to have brought about novel and complex molecules of definite prebiotic interest such as polyethers.”
Pizzarello and her team hydrothermally treated fragments of the meteorite and then detected the compounds released by gas chromatography-mass spectrometry. The hydrothermal conditions of the experiments, which also mimic early Earth settings (a proximity to volcanic activity and impact craters), released a complex mixture of oxygen-rich compounds, the probable result of oxidative processes that occurred in the parent body. They include a variety of long chain linear and branched polyethers, whose number is quite bewildering.
This addition to the inventory of organic compounds produced in extraterrestrial environments furthers the discourse of whether their delivery to the early Earth by comets and meteorites might have aided the molecular evolution that preceded the origins of life.
Note : The above story is based on materials provided by Arizona State University.
Earth’s Moon, as imaged by the Galileo mission. (Credit: NASA/JPL/USGS)
Water found in ancient Moon rocks might have actually originated from the proto-Earth and even survived the Moon-forming event. Latest research into the amount of water within lunar rocks returned during the Apollo missions is being presented by Jessica Barnes at the European Planetary Science Congress in London on Monday 9th September.
The Moon, including its interior, is believed to be much wetter than was envisaged during the Apollo era. The study by Barnes and colleagues at The Open University, UK, investigated the amount of water present in the mineral apatite, a calcium phosphate mineral found in samples of the ancient lunar crust.
“These are some of the oldest rocks we have from the Moon and are much older than the oldest rocks found on Earth. The antiquity of these rocks make them the most appropriate samples for trying to understand the water content of the Moon soon after it formed about 4.5 billion years ago and for unravelling where in the Solar System that water came from,” Barnes explains.
Barnes and her colleagues have found that the ancient lunar rocks contain appreciable amounts of water locked into the crystal structure of apatite. They also measured the hydrogen isotopic signature of the water in these lunar rocks to identify the potential source(s) for the water.
“The water locked into the mineral apatite in the Moon rocks studied has an isotopic signature very similar to that of the Earth and some carbonaceous chondrite meteorites,” says Barnes. “The remarkable consistency between the hydrogen composition of lunar samples and water-reservoirs of the Earth strongly suggests that there is a common origin for water in the Earth-Moon system.”
This research has been funded by the UK Science and Technologies Facilities Council (STFC).
Note : The above story is based on materials provided by Europlanet Media Centre.
Jud Partin inspects a stalagmite in Taurius Cave on the island of Espiritu Santo, Vanuatu. A stalagmite such as this one could be used in a paleoclimate reconstruction. (Credit: Image courtesy of University of Texas at Austin)
A new reconstruction of climate in the South Pacific during the past 446 years shows rainfall varied much more dramatically before the start of the 20th century than after. The finding, based on an analysis of a cave formation called a stalagmite from the island nation of Vanuatu, could force climate modelers to adjust their models. The models are adjusted to match the current levels of climate variability that are smaller now than they were in the recent past for this region.
“In this case, the present is not the key to the past, nor the future,” says Jud Partin, a research scientist associate at The University of Texas at Austin’s Institute for Geophysics who led the study. The institute is part of the Jackson School of Geosciences. “Instead, the past is the key to what may happen in the future.”
The researchers also discovered a roughly 50 year cycle of rainfall in Vanuatu, toggling between wet and dry periods. Vanuatu lies within the largest rain band in the southern hemisphere, the South Pacific Convergence Zone and its rainy season is from November to April. In the 20th century, rainfall during wet periods was about 7 feet per rainy season and during dry periods about 4 ½ feet per rainy season.
However, before the 20th century, the dry periods tended to be much drier, with rainfall as low as 1 foot per rainy season and wet periods that were still getting about 7 feet per rainy season. This means there were differences as large as 6 feet per rainy season between dry and wet periods.
“Without this record, you would not guess that this area could experience such large changes in rainfall,” says Partin.
While 20th century rainfall in Vanuatu experienced a smaller range from wet to dry periods than in the previous centuries, the biggest difference was during the dry periods. Dry periods in the 20th century were much wetter than dry periods in previous centuries. The researchers note that this overall wettening of Vanuatu is consistent with the hypothesis that anthropogenic climate change, caused by the emission of greenhouse gases, makes wet areas wetter and dry areas drier.
The study was published online on September 6 in the journal Geology.
Stalagmites are rocky features that form on the floors of caves as water dripping from above deposits minerals over time. By analyzing the abundance of oxygen isotopes deposited in the minerals of one particular stalagmite, the scientists were able to reconstruct a history of rainfall going back 446 years. This is significant because rainfall measurements in this region are sparse and only span the past century. Decadal averages of oxygen isotopes increase and decrease in lockstep with rainfall. To convert oxygen isotope levels to actual rainfall values, the researchers calibrated the stalagmite data with actual rainfall measurements in Vanuatu from 1904 to 2003.
The stalagmite had a deposition rate about 100 times as high as typical stalagmites in the region, meaning much more material was deposited in a given year than elsewhere and therefore yielded a much higher resolution rainfall record than is typically possible. In the local dialect, known as Bislama, one would say of the stalagmite “Hem gudfala ston,” which means “This is a good stone.”
The 50-year cycle of rainfall in Vanuatu does not appear to be linked to any external forces, such as changes in solar intensity. No correlation was found with the sun’s regular 11-year cycle of intensity or the Little Ice Age, a multi-decade change in climate possibly caused by solar dimming.
Instead, the researchers propose that the 50-year cycle, or Pacific Decadal Variability (PDV), arises from natural fluctuations in Earth’s climate. The PDV causes the South Pacific Convergence Zone to shift northeast and southwest over time. At times, the zone is over Vanuatu (corresponding to wet times) and at others, it is farther to the northeast (corresponding to dry times).
“This new result is part of a larger research program aimed at understanding climate changes in this important but understudied area of the tropical Pacific,” says co-author Terry Quinn, director and research professor at the Institute for Geophysics and professor in the Department of Geological Sciences.
Partin’s other co-authors at The University of Texas at Austin are Frederick Taylor, Charles Jackson and Christopher Maupin at the Institute for Geophysics and Jay Banner at the Department of Geological Sciences. Other co-authors are Chuan-Chou “River” Shen and Ke Lin at National Taiwan University; Julien Emile-Geay at the University of Southern California, Los Angeles; Daniel Sinclair at Rutgers University; and Chih-An Huh at Academia Sinica, Taiwan.
Funding for this research was provided by the National Science Foundation (award AGS-1003700) to Jud Partin, the Taiwan (Republic of China) National Science Council and National Taiwan University.
Note : The above story is based on materials provided by University of Texas at Austin.
This is a map view of seismic shear-wave speed in the earth’s upper mantle, highlighting the slow wave-speed channels (warm colors) imaged in this study. Where present, the channels align with the direction of tectonic-plate motion (dashed lines).Credit: Berkeley Seismological Laboratory, UC Berkeley
Berkeley — Scientists at the University of California, Berkeley, have detected previously unknown channels of slow-moving seismic waves in Earth’s upper mantle, a discovery that helps explain “hotspot volcanoes” that give birth to island chains such as Hawaii and Tahiti.
Unlike volcanoes that emerge from collision zones between tectonic plates, hotspot volcanoes form in the middle of the plates. The prevalent theory for how a mid-plate volcano forms is that a single upwelling of hot, buoyant rock rises vertically as a plume from deep within Earth’s mantle the layer found between the planet’s crust and core and supplies the heat to feed volcanic eruptions.
However, some hotspot volcano chains are not easily explained by this simple model, suggesting that a more complex interaction between plumes and the upper mantle is at play, said the study authors.
The newfound channels of slow-moving seismic waves, described in a paper to be published Thursday, Sept. 5, in Science Express, provide an important piece of the puzzle in the formation of these hotspot volcanoes and other observations of unusually high heat flow from the ocean floor.
The formation of volcanoes at the edges of plates is closely tied to the movement of tectonic plates, which are created as hot magma pushes up through fissures in mid-ocean ridges and solidifies. As the plates move away from the ridges, they cool, harden and get heavier, eventually sinking back down into the mantle at subduction zones.
But scientists have noticed large swaths of the seafloor that are significantly warmer than expected from this tectonic plate-cooling model. It had been suggested that the plumes responsible for hotspot volcanism could also play a role in explaining these observations, but it was not entirely clear how.
“We needed a clearer picture of where the extra heat is coming from and how it behaves in the upper mantle,” said the study’s senior author, Barbara Romanowicz, UC Berkeley professor of earth and planetary sciences and a researcher at the Berkeley Seismological Laboratory. “Our new finding helps bridge the gap between processes deep in the mantle and phenomenon observed on the earth’s surface, such as hotspots.”
The researchers utilized a new technique that takes waveform data from earthquakes around the world, and then analyzed the individual “wiggles” in the seismograms to create a computer model of Earth’s interior. The technology is comparable to a CT scan.
The model revealed channels dubbed “low-velocity fingers” by the researchers where seismic waves traveled unusually slowly. The fingers stretched out in bands measuring about 600 miles wide and 1,200 miles apart, and moved at depths of 120-220 miles below the seafloor.
Seismic waves typically travel at speeds of 2.5 to 3 miles per second at these depths, but the channels exhibited a 4 percent slowdown in average seismic velocity.
“We know that seismic velocity is influenced by temperature, and we estimate that the slowdown we’re seeing could represent a temperature increase of up to 200 degrees Celsius,” said study lead author Scott French, UC Berkeley graduate student in earth and planetary sciences.
The formation of channels, similar to those revealed in the computer model, has been theoretically suggested to affect plumes in Earth’s mantle, but it has never before been imaged on a global scale. The fingers are also observed to align with the motion of the overlying tectonic plate, further evidence of “channeling” of plume material, the researchers said.
“We believe that plumes contribute to the generation of hotspots and high heat flow, accompanied by complex interactions with the shallow upper mantle,” said French. “The exact nature of those interactions will need further study, but we now have a clearer picture that can help us understand the ‘plumbing’ of Earth’s mantle responsible for hotspot volcano islands like Tahiti, Reunion and Samoa.”
Note : The above story is based on materials provided by University of California – Berkeley
