back to top
27.8 C
New York
Friday, November 15, 2024
Home Blog Page 312

New fossils push the origin of flowering plants back by 100 million years to the early Triassic

This image shows flower-like pollen from the Triassic. Credit: UZH

Flowering plants evolved from extinct plants related to conifers, ginkgos, cycads, and seed ferns. The oldest known fossils from flowering plants are pollen grains. These are small, robust and numerous and therefore fossilize more easily than leaves and flowers.
An uninterrupted sequence of fossilized pollen from flowers begins in the Early Cretaceous, approximately 140 million years ago, and it is generally assumed that flowering plants first evolved around that time. But the present study documents flowering plant-like pollen that is 100 million years older, implying that flowering plants may have originated in the Early Triassic (between 252 to 247 million years ago) or even earlier.

Many studies have tried to estimate the age of flowering plants from molecular data, but so far no consensus has been reached. Depending on dataset and method, these estimates range from the Triassic to the Cretaceous. Molecular estimates typically need to be “anchored” in fossil evidence, but extremely old fossils were not available for flowering plants. “That is why the present finding of flower-like pollen from the Triassic is significant”, says Prof. Peter Hochuli, University of Zurich.

Peter Hochuli and Susanne Feist-Burkhardt from Paleontological Institute and Museum, University of Zürich, studied two drilling cores from Weiach and Leuggern, northern Switzerland, and found pollen grains that resemble fossil pollen from the earliest known flowering plants. With Confocal Laser Scanning Microscopy, they obtained high-resolution images across three dimensions of six different types of pollen.

In a previous study from 2004, Hochuli and Feist-Burkhardt documented different, but clearly related flowering-plant-like pollen from the Middle Triassic in cores from the Barents Sea, south of Spitsbergen. The samples from the present study were found 3000 km south of the previous site. “We believe that even highly cautious scientists will now be convinced that flowering plants evolved long before the Cretaceous”, say Hochuli.

What might these primitive flowering plants have looked like? In the Middle Triassic, both the Barents Sea and Switzerland lay in the subtropics, but the area of Switzerland was much drier than the region of the Barents Sea. This implies that these plants occurred a broad ecological range. The pollen’s structure suggests that the plants were pollinated by insects: most likely beetles, as bees would not evolve for another 100 million years.

Note : The above story is based on materials provided by Prof Peter A. Hochuli For University of Zürich

Geological exploration reveals Australian super volcano

The Palgrave region in the Musgrave Ranges. Credit: M Werner, Geological Survey of WA

A geological survey team says an ancient super volcano exuded more than 450 cubic kilometres of molten magma in a single eruption, over what are now Ngaanyatjarra tribal lands.

Geochemist Dr Hugh Smithies says it is the largest super volcano he is aware of on the planet.

“It was active for likely in excess of 30 million years,” he says.

“The typical lifespan of volcanic systems is usually measured in the many hundreds of thousands of years, up to a couple of million, but certainly 30 million is just extraordinary.”

Dr Smithies says the eruption occurred at the point where three tectonic plates converged.

He says the earth’s crust had been unusually hot in this location for some 200 million years beforehand, partly due to the North Australian, Western Australian and South Australian Cratons attempting to pull apart.

“I refer to it as a chronically frustrated rift,” he says.

“This region has contained some of the hottest crust that the world’s ever known.

“The magmas … produced in that prior 200 million years [were] very thorium rich … producing a lot of radiogenic heat keeping the area hot as well.

Dr Smithies and his team found the super volcano while exploring the Musgrave Ranges in the Western Desert for the Geological Survey of Western Australia.

“It involves systematic mapping and systematic geochemical sampling to try and gauge what the geochemical variations in the magmas were,” he says.

“This was a particularly interesting part of the geology of the region that we spent a bit more time on than we normally do.

“The mapping allowed us to estimate the volumes of erupted material and that’s where the super eruption concept comes from.

“They’re defined as single eruptions that have volumes in excess of 450 cubic kilometres.

“The mapping allows us to establish the unit we’re looking at, mapping as a single depositional unit, and to estimate the actual volumes.

He says super volcanoes are relatively rare phenomena, and this one may be unique for Australia.

The area is part of a fully-determined native title claim, and he was keen to acknowledge the traditional owners’ participation.

“This whole project has been a joint project with the Indigenous people of that region,” Dr Smithies says.

“In terms of economic potential there’s obviously a lot of hyperthermal alteration associated with big volcanic systems and so it possibly heralds a hitherto unrecognised gold area that’s potentially conducive to gold mineralisation.”

Note : The above story is based on materials provided by Science Network WA

NASA Mars Rover Curiosity Finds Water in First Sample of Planet Surface

On Sol 84 (Oct. 31, 2012), NASA’s Curiosity rover used the Mars Hand Lens Imager (MAHLI) to capture this set of 55 high-resolution images, which were stitched together to create this full-color self-portrait of the rover at “Rocknest.” (Credit: NASA/JPL-Caltech/Malin Space Science Systems)

The first scoop of soil analyzed by the analytical suite in the belly of NASA’s Curiosity rover reveals that fine materials on the surface of the planet contain several percent water by weight. The results were published today in Science as one article in a five-paper special section on the Curiosity mission. Rensselaer Polytechnic Institute Dean of Science Laurie Leshin is the study’s lead author.

“One of the most exciting results from this very first solid sample ingested by Curiosity is the high percentage of water in the soil,” said Leshin. “About 2 percent of the soil on the surface of Mars is made up of water, which is a great resource, and interesting scientifically.” The sample also released significant carbon dioxide, oxygen, and sulfur compounds when heated.

Curiosity landed in Gale Crater on the surface of Mars on August 6, 2012, charged with answering the question “Could Mars have once harbored life?” To do that, Curiosity is the first rover on Mars to carry equipment for gathering and processing samples of rock and soil. One of those instruments was employed in the current research: Sample Analysis at Mars (SAM) includes a gas chromotograph, a mass spectrometer, and a tunable laser spectrometer enabling it to identify a wide range of chemical compounds and determine the ratios of different isotopes of key elements.

“This work not only demonstrates that SAM is working beautifully on Mars, but also shows how SAM fits into Curiosity’s powerful and comprehensive suite of scientific instruments,” said Paul Mahaffy, principal investigator for SAM at NASA’s Goddard Space Flight Center in Maryland. “By combining analyses of water and other volatiles from SAM with mineralogical, chemical, and geological data from Curiosity’s other instruments, we have the most comprehensive information ever obtained on martian surface fines. These data greatly advance our understanding of surface processes and the action of water on Mars.”

“This is the first solid sample that we’ve analyzed with the instruments on Curiosity. It’s the very first scoop of stuff that’s been fed into the analytical suite. Although this is only the beginning of the story, what we’ve learned is substantial,” said Leshin, who co-wrote the article, titled “Volatile, Isotope and Organic Analysis of Martian Fines with the Mars Curiosity Rover.” Thirty-four researchers, all members of the Mars Science Laboratory Science Team, contributed to the paper.

In this study, scientists used the rover’s scoop to collect dust, dirt, and finely grained soil from a sandy patch known as “Rocknest.” Researchers fed portions of the fifth scoop into SAM. Inside SAM, the “fines” — as the dust, dirt, and fine soil is known — were heated to 835 degrees Celsius.

Baking the sample also revealed a compound containing chlorine and oxygen, likely chlorate or perchlorate, previously known only from high-latitude locations on Mars. This finding at Curiosity’s equatorial site suggests more global distribution. The analysis also suggests the presence of carbonate materials, which form in the presence of water.

In addition to determining the amount of the major gases released, SAM also analyzed ratios of isotopes of hydrogen and carbon in the released water and carbon dioxide. Isotopes are variants of the same chemical element with different numbers of neutrons, and therefore different atomic weights. SAM found that the ratio of isotopes in the soil is similar to that found in the atmosphere analyzed earlier by Curiosity, indicating that the surface soil has interacted heavily with the atmosphere.

“The isotopic ratios, including hydrogen-to-deuterium ratios and carbon isotopes, tend to support the idea that as the dust is moving around the planet, it’s reacting with some of the gases from the atmosphere,” Leshin said.

SAM can also search for trace levels of organic compounds. Although several simple organic compounds were detected in the experiments at Rocknest, they aren’t clearly martian in origin. Instead, it is likely that they formed during the heating experiments, as the non-organic compounds in Rocknest samples reacted with terrestrial organics already present in the SAM instrument background.

“We find that organics are not likely preserved in surface soils, which are exposed to harsh radiation and oxidants,” said Leshin. “We didn’t necessarily expect to find organic molecules in the surface fines, and this supports Curiosity’s strategy of drilling into rocks to continue the search for organic compounds. Finding samples with a better chance of organic preservation is key.”

The results shed light on the composition of the planet’s surface, while offering direction for future research, said Leshin.

“Mars has kind of a global layer, a layer of surface soil that has been mixed and distributed by frequent dust storms. So a scoop of this stuff is basically a microscopic Mars rock collection,” said Leshin. “If you mix many grains of it together, you probably have an accurate picture of typical martian crust. By learning about it in any one place, you’re learning about the entire planet.”

These results have implications for future Mars explorers. “We now know there should be abundant, easily accessible water on Mars,” said Leshin. “When we send people, they could scoop up the soil anywhere on the surface, heat it just a bit, and obtain water.”

In addition to her work research as part of the Mars Science Laboratory Team, Leshin is Dean of the School of Science at Rensselaer Polytechnic Institute, where she leads the scientific academic and research enterprise at the nation’s first technological university.

Note : The above story is based on materials provided by Rensselaer Polytechnic Institute. 

Study finds tungsten in aquifer groundwater controlled by pH, oxygen

Chad Hobson, master’s student in geology, Lavonia, Ga., collects sediment samples from Cheyenne Bottoms in Hoisington, Kan.

MANHATTAN — Two Kansas geologists are helping shed new light on how tungsten metal is leached from the sediment surrounding aquifers into the groundwater. The findings may have implications for human health.

Tungsten is a naturally occurring metal that is primarily used for incandescent light bulb filaments, drill bits and an alternative to lead in bullets. Though it is thought to be nonhazardous to the environment and nontoxic to humans, it can be poisonous if ingested in large amounts. In recent years, tungsten has been tentatively linked to cases of childhood leukemia in the Western U.S.

“Very little is known about the biogeochemistry of tungsten in the environment,” said Saugata Datta, professor of geology at Kansas State University. “We need to understand how this metal is leached from the soils into groundwater because humans can be exposed to tungsten through multiple pathways.”

Datta, along with Chad Hobson, master’s student in geology, Lavonia, Ga., and colleagues at Tulane University and the University of Texas, Arlington, found that the likelihood that tungsten will seep into an aquifer’s groundwater depends on the groundwater’s pH level, the amount of oxygen in the aquifer and the number of oxidized particles in the water and sediment. Analysis also showed that tungsten-VI is the most common form of tungsten in natural sediments.

These latest findings appear in the study “Controls on tungsten concentrations in groundwater flow systems: The role of adsorption, aquifer sediment Fe(III) oxide/oxyhydroxide content, and thiotungstate formation,” published in the journal Chemical Geology.

In addition to the publication, Datta and Hobson presented the findings at the International Conference on Biogeochemistry of Trace Elements.

For the study, researchers looked at Fallon, Nev.; Sierra Vista, Ariz.; and at the Cheyenne Bottoms Refuge near Hoisington, Kan. The sites were chosen based on previous studies analyzing plants and dust collected on trees in the locations. Additionally, these areas have natural tungsten mineral deposits, nearby military bases, and mining and smelting operations in the area, Datta said.

In 2002, the Centers for Disease Control investigated several clusters of acute lymphatic leukemia in both Nevada and Arizona. The investigation found that residents’ urine had tungsten levels above the 95th percentile.

“This was important for us to know because the goal is to clarify valuable information about tungsten’s geochemistry,” Datta said. “So, we needed sites that had tungsten — and enough tungsten to measure easily. The benefit of this study is that tungsten’s geochemistry has been overlooked and until recently, largely unknown. This work will help fill the gaps in the knowledge of tungsten, which is possibly carcinogenic, and help determine its future use.”

Datta and Hobson analyzed sediment samples lining the aquifers while researchers at Tulane University and the University of Texas, Arlington analyzed the groundwater samples. The National Synchrotron Light Source was used for spectroscopic analysis of the individual particles. This helped researchers understand the speciation of tungsten in natural sediments in the environment and helped them detect why tungsten forms organosulphur complexes that can be soluble in groundwater, Datta said. Analysis also showed that tungsten-VI is the most common form of tungsten in natural sediments.

Analysis of the sediment and groundwater showed that iron oxide and oxyhydroxide particles in both substances play a key role in regulating how much tungsten is in the groundwater. The fewer iron oxides or oxyhydroxide particles, the higher the amount of tungsten, Datta said.

Similarly, the team found that the number of tungsten-regulating iron oxide particles is controlled by the pH in the groundwater. A higher pH results in more tungsten entering the water.

“Tungsten is specifically bound to these iron oxides and oxyhydroxides,” Datta said. “One of the major factors controlling tungsten’s mobility and bioavailability is pH. Ranging values of pH can affect how tungsten behaves or transforms between different tungsten species, which have different properties and factors controlling mobility.”

When tungsten is in the water it is surrounded by oxygen atoms and forms an anion, Datta said. When in the presence of phosphates, this anion tends to bind with other transition metals, commonly iron, to form poloyoxometalates. In this form, tungsten can become more soluble in water.

Researchers also found that aquifers with less dissolved oxygen had greater traces of tungsten in the groundwater than aquifers with high dissolved oxygen levels.

The process of tungsten being leached from the surrounding sediment into the groundwater can be reduced if the ironoxides are in the water and the water has a neutral pH level, according to Datta.

The study is part of a three-year, $515,000 National Science Foundation-funded project between Kansas State University and Karen Johannesson at Tulane University that is titled “Collaborative Research: Chemical Hydrogeologic Investigations of Tungsten: Field, Laboratory, and Modeling Studies of an Emerging Environmental Contaminant.” It focuses on biogeochemistry of tungsten’s reaction to the environment and how it is transported from sediments into groundwaters once it becomes geochemically mobilized.

Note : The above story is based on materials provided by Kansas State University

Research duo suggest early Earth had heat-pipe channels similar to Jupiter’s moon

Credit: Nature

Two planetary researches, one from Hampton University and the National Institute of Aerospace, the other from Louisiana State University, have published a paper in the journal Nature suggesting that for a period of time, the Earth was very similar to Jupiter’s moon Io—with heat from within being released through what are known as heat-pipes. The new theory by William Moore and Alexander Webb goes against the common consensus that the Earth transitioned directly from a planet with a hot molten liquid layer to one covered by tectonic plates.

Planetary scientists have been stumped in trying to figure out how a planet with a molten hot liquid surface could transition directly to one with tectonic plates—the only way that could happen would be if the planet cooled almost instantly. But all available evidence indicates it didn’t, so how did the tectonic plates come about? Moore and Webb suggest there was an intermediate stage—one where heat was allowed to escape from the interior of the planet through heat-pipes.

In practical terms, heat pipes are soft material “holes” in a planet’s surface. Hot magma from below is pushed upwards through channels towards the surface where it flows out as lava allowing heat to escape into space. While very similar to volcanoes, they don’t necessarily erupt, they simply ooze. Jupiter’s moon Io is an excellent example of a body that oozes lava, with so many heat-pipes that its entire surface is covered by material constantly pushed up from below. The result is a constant turnover of surface material, mixing with that from below. Moore and Webb theorize that a very similar situation existed on Earth between the time the surface was hot molten liquid and the development of tectonic plates. They suggest the constant movement of material up though the heat-pipes led to a build-up on the surface. As the planet cooled over time, the material that was pushed up slowly hardened and became the tectonic plates. And because there was still a lot of heat in the core of the planet, fissures developed which caused the plates to break apart and to travel as they continue to do today.

Moore and Webb point to ancient zircon and diamonds found on Earth to strengthen their theory—the rocks have been dated to the time period in question (roughly 3 to 4 billion years ago) and show the weathering that would have occurred had they been constantly churned by heat-pipe transport.

More information: Heat-pipe Earth, Nature 501, 501–505 (26 September 2013)
DOI: 10.1038/nature12473

Note : The above story is based on materials provided by Nature

Scientists push closer to understanding mystery of deep earthquakes

LEMONT, Ill. – Scientists broke new ground in the study of deep earthquakes, a poorly understood phenomenon that occurs where the oceanic lithosphere, driven by tectonics, plunges under continental plates – examples are off the coasts of the western United States, Russia and Japan.

This research is a large step toward replicating the full power of these earthquakes to learn what sets them off and how they unleash their violence. It was made possible only by the construction of a one-of-a-kind X-ray facility that can replicate high-pressure and high-temperature while allowing scientists to peer deep into material to trace the propagation of cracks and shock waves.

“We are capturing the physics of deep earthquakes,” said Yanbin Wang, a senior scientist at the University of Chicago who helps run the X-ray facility where the research occurred. “Our experiments show that, for the first time, laboratory-triggered brittle failures during the olivine-spinel (mineral) phase transformation has many similar features to deep earthquakes.”

Wang and a team of scientists from Illinois, California and France simulated deep earthquakes at the U.S. Department of Energy’s Argonne National Laboratory by using pressure of 5 gigapascals, more than double the previous studies of 2 GPa. For comparison, pressure of 5 GPa is 4.9 million times the pressure at sea level.

At this pressure, rock should be squeezed too tight to rapture and erupt into violent earthquakes. But it does. And that has puzzled scientists since the phenomenon of deep earthquakes was discovered nearly 100 years ago. Interest spiked with the May 24 eruption in the waters near Russia of the world’s strongest deep earthquake – roughly five times the power of the great San Francisco quake of 1906.

These deep earthquakes occur in older and colder areas of the oceanic plate that gets pushed into the earth’s mantle. It has been speculated that the earthquakes are triggered when a mineral common in the upper mantle,  olivine, undergoes a phase transformation that weakens the whole rock temporarily, causing it to fail.

“Our current goal is to understand why and how deep earthquakes happen. We are not at a stage to predict them yet; it is still a long way to go,” Wang said.

The work was conducted at the GeoSoilEnviroCARS beamline operated by the University of Chicago at Argonne’s Advanced Photon Source.

“GSECARS is the only beamline in the world that has the combined capabilities of in-situ X-ray diffraction and imaging, controlled deformation, in terms of stress, strain and strain rate, at high pressure and temperature, and acoustic emission detection,” Wang said. “ It took us several years to reach this technical capability.”

This new technology is a dream come true for the paper’s coauthor, geologist Harry Green, a distinguished professor of the graduate division at the University of California, Riverside.

More than 20 years ago, he 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 the 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 explained how to simulate these earthquakes in a paper titled “Deep-Focus Earthquake Analogs Recorded at High Pressure and Temperature 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 experiment — 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 the 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.”

“Our next goal is to study the ‘real’ material, the silicate olivine (Mg,Fe)2SiO4, which requires much higher pressures,” Wang said.

The research was funded by grants from the Institut National des Sciences de l’Univers and L’Agence Nationale de la Recherche and the National Science Foundation. Use of the Advanced Photon Source was funded by U.S. Department of Energy Office of Science.

The authors of the study were Alexandre Schubnel at the Ecole Normale Supérieure, France; Fabrice Brunet at the Université de Grenoble, France; Julian Gasc and Wang at the University of Chicago; Nadège Hilairet at the University of Chicago and UMET, CNRS – Université Lille 1;  and Green of UC Riverside.

Researchers describe unusual Mars rock

Raw image of Jake_M taken by the left mast camera (mastcam) (0046ML0212000000E1) with overlain images from MAHLI at 26.9-, 6.9-, and 4.4-cm offsets from the front of the lens. The MAHLI projection on the left was taken at 4.4 cm (0047MH0011002000E1). Shadowing by the turret reduced the contrast in the inset MAHLI images, causing color differences with the mastcam image. The solid red circles labeled JM1 and JM2 indicate the locations of the two APXS spots (1.7-cm diameter). ChemCam raster spots are represented by yellow open circles; actual spot sizes are ~0.45 mm. This image relates to the paper by Dr. Stolper et al. Credit: NASA/Jet Propulsion Laboratory–Caltech/Malin Space Science Systems. Credit: Science/AAAS

CORVALLIS, Ore. – The first rock that scientists analyzed on Mars with a pair of chemical instruments aboard the Curiosity rover turned out to be a doozy – a pyramid-shaped volcanic rock called a “mugearite” that is unlike any other Martian igneous rock ever found.

Dubbed “Jake_M” – after Jet Propulsion Laboratory engineer Jake Matijevic – the rock is similar to mugearites found on Earth, typically on ocean islands and in continental rifts. The process through which these rocks form often suggests the presence of water deep below the surface, according to Martin Fisk, an Oregon State University marine geologist and member of the Mars Science Laboratory team.

Results of the analysis were published this week in the journal Science, along with two other papers on Mars’ soils.

“On Earth, we have a pretty good idea how mugearites and rocks like them are formed,” said Fisk, who is a co-author on all three Science articles. “It starts with magma deep within the Earth that crystallizes in the presence of 1-2 percent water. The crystals settle out of the magma and what doesn’t crystallize is the mugearite magma, which can eventually make its way to the surface as a volcanic eruption.”

Fisk, who is a professor in OSU’s College of Earth, Ocean, and Atmospheric Sciences, said the most common volcanic rocks typically crystallize in a specific order as they cool, beginning with olivine and feldspar. In the presence of water, however, feldspar crystallizes later and the magma will have a composition such as mugearite.

Although this potential evidence for water deep beneath the surface of Mars isn’t ironclad, the scientists say, it adds to the growing body of studies pointing to the presence of water on the Red Planet – an ingredient necessary for life.

“The rock is significant in another way,” Fisk pointed out. “It implies that the interior of Mars is composed of areas with different compositions; it is not well mixed. Perhaps Mars never got homogenized the way Earth has through its plate tectonics and convection processes.”

In another study, scientists examined the soil diversity and hydration of Gale Crater using a ChemCam laser instrument. They found hydrogen in all of the sites sampled, suggesting water, as well as the likely presence of sulphates. Mars was thought to have three stages – an early phase with lots of water, an evaporation phase when the water disappeared leaving behind sulphate salts, and a third phase when the surface soils dried out and oxidized – creating the planet’s red hue.

“ChemCam found hydrogen in almost every place we found iron,” Fisk said.

The third study compared grains of rock on the surface with a darker soil beneath at a site called the Rocknest Sand Shadow. Some of the sand grains are almost perfectly round and may have come from space, Fisk said.

Note : The above story is based on materials provided by Oregon State University

Breathing Underwater: Evidence of Microscopic Life in Oceanic Crust

Dr. Beth Orcutt (front, second from left) of Bigelow Laboratory for Ocean Sciences examines oceanic crust samples with Dr. Wolfgang Bach of the University of Bremen, Germany, during IODP Expedition 336 to the Mid-Atlantic Ridge flank. (Credit: Photo courtesy of Jennifer T. Magnusson.)

Although long thought to be devoid of life, the bottom of the deep ocean is now known to harbor entire ecosystems teeming with microbes. Scientists have recently documented that oxygen is disappearing from seawater circulating through deep oceanic crust, a significant first step in understanding the way life in the “deep biosphere” beneath the sea floor is able to survive and thrive. The new research findings were published in the journal Nature Communications on September 27, 2013, and are helping to redefine our concepts of the limits of life on our planet.

A team of researchers led by Dr. Beth Orcutt of the Bigelow Laboratory for Ocean Sciences used the JOIDES Resolution, a sophisticated 470-foot scientific drilling vessel operated by the international Integrated Ocean Drilling Program (IODP), to sample the muddy and sandy sediments that blanket the rocks on the seafloor, as well as drill into the hard crustal rocks themselves — considered by many to be the largest reservoir of life on Earth — in order to understand how microbes can “breathe” and get the energy necessary to live in this remote environment.

The team measured oxygen concentrations in sediment cores collected above the rocky oceanic crust, almost three miles below the sea surface, on the western edge of the remote Mid-Atlantic Ridge. These measurements then allowed the researchers to determine oxygen concentration in seawater circulating in the rocks of the oceanic crust itself.

“Our computer models showed that the crustal oxygen concentrations in the region were most likely the result of microbial life forms scavenging oxygen in the crust as seawater moves through fractures and cracks deep in the rocks,” said Orcutt. “Under the cold conditions of the crust in this area, purely chemical oxygen consumption is minimal, which suggests that microbes in the oceanic crust are responsible for using the oxygen that’s down there.”

“We know there’s a vast reservoir of life in the ocean crust, but unless we take steps to quantify its metabolism, we’ll never know how vast it is,” said co-author Dr. Sam Hulme, from Moss Landing Marine Laboratories.

Another co-author of the paper, Dr. Geoff Wheat of the University of Alaska Fairbanks, pointed out that chemical composition of seawater within pore spaces between sediment grains provides important information about what reactions occur there and how fast they happen. “This result sets the stage for more directed experiments to understand how microbes use the oxygen for growth in a place with little food,” Wheat said.

“One of the biggest goals of the international scientific ocean drilling research community is to understand how life functions in the vast ‘deep biosphere’ buried alive below the seafloor, but it’s very challenging to access and explore the hard rocks that make up the base of the seafloor,” Orcutt added. “Our results are the first to document the removal of oxygen in the rocky crustal environment — something that had been expected but not shown until now. With this information, we can start to unravel the complex mystery of life below the seafloor.”

“Detecting life by measuring oxygen in subseafloor environments with vigorous seawater flow is not an easy task,” agreed Dr. Wolfgang Bach, a scientist at the University of Bremen in Germany, and another coauthor of the paper. “Imagine an extraterrestrial life-detection task force landing on Earth with oxygen probes as the only life-detection tool. If they ended up in a well-ventilated meeting room stuffed with delegates, they’d conclude from the measurements they’d be making that respiration was minimal, hence life is slow, if not absent. Doing these measurements in an environment where we think we know the direction of flow of seawater and detecting a gradient in oxygen makes all the difference in making inferences about subseafloor life.”

“Tiny microbial life on Earth is responsible for big tasks like global chemical cycling. In order to understand how important elements like oxygen — which we all need to breathe — move around Earth, we need to understand how quickly it is consumed in the largest aquifer on Earth, oceanic crust,” said Orcutt.

Note : The above story is based on materials provided by Bigelow Laboratory for Ocean Sciences. 

Late Cretaceous Period Was Likely Ice-Free

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.

Ancient Soils Reveal Clues to Early Life On Earth

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. 

Formation of Unusual Ring of Radiation Around Earth Explained

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.

Study shows volcanic eruptions beneath bodies of water can cause widespread dispersal of diatoms

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

Dinosaur Wind Tunnel Test Provides New Insight Into the Evolution of Bird Flight

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. 

Geologists Simulate Deep Earthquakes in Lab

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.

Seismologists Puzzle Over Largest Deep Earthquake Ever Recorded

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.

Earth Expected to Be Habitable for Another 1.75 Billion Years

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.”

Note : The above story is based on materials provided by University of East Anglia. 

‘Cascade of Events’ Caused Sudden Explosion of Animal Life

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. 

What Direction Does Earth’s Center Spin? New Insights Solve 300-Year-Old Problem

Scientists 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. (Credit: © KristijanZontar / Fotolia)

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. 

Computer simulation sheds light on how Earth’s continents were born

University of Calgary Geoscience professor David Eaton has published a paper that provides new insights into the birth of continents.
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.

Note : The above story is based on materials provided by University of Calgary. 

Columnar Basalt , Mendisha Mountain , Egypt

Columnar Basalt , Mendisha Mountain , Egypt © www.geologypage.com

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).

Table of Contents

Photos :

Columnar Basalt , Mendisha Mountain , Egypt © www.geologypage.com
Columnar Basalt , Mendisha Mountain , Egypt © www.geologypage.com
Basaltic Blisters , Mendisha Mountain , Egypt © www.geologypage.com
Basaltic Blisters , Mendisha Mountain , Egypt © www.geologypage.com
Basaltic Blisters , Mendisha Mountain , Egypt © www.geologypage.com

Video :

Note :  The above story is based on materials provided by “Hussein and Sharkawi, 1990”
Photo & Video : © www.geologypage.com

1...311312313...333Page 312 of 333

Related Articles

All
Facebook Instagram Linkedin TikTok Twitter Youtube
© © 2011-2024. All Rights Reserved.