A mysterious basin off the coast of India could be the largest, multi-ringed impact crater the world has ever seen. And if a new study is right, it may have been responsible for killing the dinosaurs off 65 million years ago.
Sankar Chatterjee of Texas Tech University and a team of researchers took a close look at the massive Shiva basin, a submerged depression west of India that is intensely mined for its oil and gas resources. Some complex craters are among the most productive hydrocarbon sites on the planet.
“If we are right, this is the largest crater known on our planet,” Chatterjee said. “A bolide of this size, perhaps 40 kilometers (25 miles) in diameter creates its own tectonics.”
By contrast, the object that struck the Yucatan Peninsula, and is commonly thought to have killed the dinosaurs was between 8 and 10 kilometers (5 and 6.2 miles) wide.
It's hard to imagine such a cataclysm. But if the team is right, the Shiva impact vaporized Earth's crust at the point of collision, leaving nothing but ultra-hot mantle material to well up in its place. It is likely that the impact enhanced the nearby Deccan Traps volcanic eruptions that covered much of western India. What's more, the impact broke the Seychelles islands off of the Indian tectonic plate, and sent them drifting toward Africa.
The geological evidence is dramatic. Shiva's outer rim forms a rough, faulted ring some 500 kilometers in diameter, encircling the central peak, known as the Bombay High, which would be 3 miles tall from the ocean floor (about the height of Mount McKinley). Most of the crater lies submerged on India's continental shelf, but where it does come ashore it is marked by tall cliffs, active faults and hot springs. The impact appears to have sheared or destroyed much of the 30-mile-thick granite layer in the western coast of India.
The team hopes to go India later this year to examine rocks drill from the center of the putative crater for clues that would prove the strange basin was formed by a gigantic impact.
“Rocks from the bottom of the crater will tell us the telltale sign of the impact event from shattered and melted target rocks. And we want to see if there are breccias, shocked quartz, and an iridium anomaly,” Chatterjee said. Asteroids are rich in iridium, and such anomalies are thought of as the fingerprint of an impact.
Monday, October 26, 2009
A mysterious basin off the coast of India could be the largest, multi-ringed impact crater the world has ever seen. And if a new study is right, it may have been responsible for killing the dinosaurs off 65 million years ago.
Members of the West Semitic Research Project at the University of Southern California are helping the University’s Oriental Institute make very high-quality electronic images of nearly 700 Aramaic administrative documents. The Aramaic texts were incised in the surfaces of clay tablets with styluses or inked on the tablets with brushes or pens. Some tablets have both incised and inked texts.
Discovered in Iran, these tablets form one of the largest groups of ancient Aramaic records ever found. They are part of the Persepolis Fortification Archive, an immense group of administrative documents written and compiled about 500 B.C. at Persepolis, one of the capitals of the Achaemenid Persian Empire. Archaeologists from the Oriental Institute discovered the archive in 1933, and the Iranian government has loaned it to the Oriental Institute since 1936 for preservation, study, analysis and publication.
The Persepolis texts have started to provide scholars with new knowledge about Imperial Aramaic, the dialect used for international communication and record-keeping in many parts of the Assyrian, Babylonian and Persian empires, including parts of the administration at the imperial court of Persepolis. These texts have even greater value because they are so closely connected with documents written in other ancient languages by the same administration at Persepolis.
“We don’t have many archives of this size. A lot of what’s in these texts is entirely fresh, but this also changes what we already knew,” said Annalisa Azzoni, an assistant professor at the Divinity School of Vanderbilt University. Azzoni is a specialist on ancient Aramaic and is now working with the Persepolis Fortification Archive Project at the Oriental Institute. “There are words I know were used in later dialects, for example, but I didn’t know they were used at this time or this place, Persia in 500 B.C. For an Aramaicist, this is quite an important discovery.”
Scholars from the West Semitic Research Project at the University of Southern California helped the Persepolis Fortification Archive Project build and install an advanced electronic imaging laboratory at the Oriental Institute. Together, the two projects are making high-quality images of the Aramaic texts and the seal impressions associated with those texts. They are distributing the new images to the international research community through the Internet.
Inked and incised texts pose different problems that call for different imaging solutions. Making high-resolution scans under polarized and filtered light reveals the ink without interference from stains and glare, and sometimes shows faded characters that cannot be seen in ordinary daylight. Using another advanced imaging technique, called Polynomial Texture Mapping, researchers are able to see surface variations under variable lighting, revealing the marks of styluses and even the traces of pens in places where the ink itself has disappeared.
Distributing the results online will give worldwide communities of philologists and epigraphers images that are almost as good as the original objects―and in some cases actually clearer than the originals―to study everything from vocabulary and grammar to the handwriting habits of individual ancient scribes.
Researcher Marilyn Lundberg and her colleagues from the West Semitic Research Project built two Polynomial Texture Mapping devices from scratch at the Oriental Institute. They trained Persepolis Fortification Archive Project workers in using them, and also in using filtered light with a camera equipped with a high-resolution scanning device. Now a stream of raw images is uploaded every day to a dedicated server maintained by Humanities Research Computing at Chicago, then uploaded for post-processing at the University of Southern California. Fully processed imagery is available on InscriptiFact, the online application of the West Semitic Research Project, and in the Online Cultural Heritage Research Environment, the online application of the Persepolis Fortification Archive Project.
The Polynomial Texture Mapping apparatus looks a bit like a small astronomical observatory, with a cylindrical based topped by a hemispherical dome. The camera takes a set of 32 pictures of each side of the tablet, with each shot lit with a different combination of 32 lights set in the dome. After post-processing, the PTM software application knits these images to allow a viewer sitting at a computer to manipulate the apparent direction, angle and intensity of the light on the object, and to introduce various effects to help with visualization of the surface.
“This means that the scholar isn’t completely dependent on the photographer for what he sees anymore,” said Bruce Zuckerman, Director of the West Semitic Research Project and its online presence, InscriptiFact. “The scholar can pull up an image on the screen and relight an object exactly as he wants to see it. He can look at different parts of the image with different lighting, to cast light and shadow across even the faintest, shallowest marks of a stylus or pen on the surface, and across every detail of a seal impression.”
“This is a wonderful way to look at seal impressions,” said Elspeth Dusinberre, another Persepolis Fortification Project collaborator. Dusinberre, an associate professor of classics at the University of Colorado, is studying the imagery and the use of seals impressed on the Aramaic tablets. “Some of the impressions are faint, or incomplete, on curved surfaces or damaged surfaces. Sometimes Aramaic text is written across them. You need to be able to move the light around to highlight every detail, to see the whole picture.”
The Persepolis Fortification Archive also includes about 10,000 to 12,000 other tablets and fragments with cuneiform texts in Elamite―a few hundred of them with short secondary texts in Aramaic. There are also about 4,000 to 5,000 others with impressions of seals, but no texts, and there are a few unique documents in other languages and scripts, including Greek, Old Persian and Phrygian.
“That’s what makes this group of Aramaic texts so extraordinary,” Stolper said. “From one segment of the Persepolis Fortification Archive, the Elamite texts, we know a lot about conditions around Persepolis at about 500 B.C. When we can add a second stream of information, the Aramaic texts, we’ll be able to see things in a whole new light. They add a new dimension of the ancient reality.”
The collaboration between the Oriental Institute at Chicago and the West Semitic Research Project at Southern California began with support from a substantial grant from the Andrew W. Mellon Foundation in 2007. To date, the teams have made high-quality images of almost all the monolingual Aramaic Fortification tablets. The next phase of the work, supported by a second Mellon grant that runs through 2010, will make images of the short Aramaic notes written on cuneiform tablets, seal impressions on uninscribed tablets and previously unrecorded Elamite cuneiform texts.
The tablets have been studied since they came to Chicago in 1936, and many of them have been sent back to Iran. Oriental Institute scholar Richard T. Hallock published about 2,100 of the Elamite texts in 1969, and Margaret Cool Root and Persepolis Fortification Archive Project collaborator Mark Garrison are completing a three-volume publication of the impressions made on those documents by about 1,500 distinct seals.
These publications have had far-reaching results. “They have transformed every aspect of modern study of the languages, history, society, institutions, art and religion of the Achaemenid Persian Empire,” Stolper said. “No serious treatment of the empire that Cyrus and Darius built and that Alexander destroyed can ignore the perspectives of the Fortification Archive.”
“If that is the effect of a sample of one component of the archive,” added Garrison, “imagine what will happen when we can have larger samples and other components, and not just the written record, but the imagery, the impressions made by thousands of different seals that administrators and travelers―the men and women who figure in the texts―employed.”
By 2010, the collaborating teams expect to have high-quality images of 5,000 to 6,000 Persepolis tablets and fragments, and to supplement these with conventional digital images of another 7,000 to 8,000 tablets and fragments. The images will be distributed online as they are processed, along with cataloging and editorial information.
“Thanks to electronic media, we don’t have to cut the parts of the archive up and distribute the pieces among academic specialties,” said Stolper. “We can combine the work of specialists in a way that lets us see the archive as it really was, in its original complexity, as one big thing with many distinct parts.”
(Photo: Oriental Institute, University of Chicago)
University of Chicago
The research, published in the Journal of Infectious Diseases, showed that the elevated body temperature of mammals – the familiar 98.6º F or 37º C in people – is too high for the vast majority of potential fungal invaders to survive.
"Fungal strains undergo a major loss of ability to grow as we move to mammalian temperatures," said Arturo Casadevall, M.D., Ph.D., chair and professor of microbiology & immunology at Einstein. Dr. Casadevall conducted the study in conjunction with Vincent A. Robert of the Utrecht, Netherlands-based Fungal Biodiversity Center, also known as Centraalbureau voor Schimmelcultures.
"Our study makes the argument that our warm temperatures may have evolved to protect us against fungal diseases," said Dr. Casadevall. "And being warm-blooded and therefore largely resistant to fungal infections may help explain the dominance of mammals after the age of dinosaurs."
There are roughly 1.5 million fungal species. Of these, only a few hundred are pathogenic to mammals. Fungal infections in people are often the result of an impaired immune function. By contrast, an estimated 270,000 fungal species are pathogenic to plants and 50,000 species infect insects. Frogs and other amphibians are prone to fungal pathogens, one of which, chytridiomycosis, is currently raging through frogs worldwide. Fungi are also important in the decomposition of plants.
In their study, the researchers investigated how 4,082 different fungal strains from the Utrecht collection grew in temperatures ranging from chilly – 4º C or 39º F – to desert hot – 45º C or 113º F. They found that nearly all of them grew well in temperatures up to 30º C. Beyond that, though, the number of successful species declined by 6 percent for every one degree centigrade increase. Most could not grow at mammalian temperatures. Those that did well in hotter conditions were often from warm-blooded sources.
Dr. Casadevall noted that the current study covered thousands of fungal strains and made use of a computerized database of the Utrecht collection. In the past, this type of research would have required retrieving this information manually, which Dr. Casadevall noted would have been a very time-consuming task.
"This was possible only because we could use bioinformatic tools to analyze the records in the culture collection," he said. "There is no way to do a study like this without such technology given the enormous numbers of samples and the labor involved."
The results of the study, he added, could help explain why mammals maintain a seemingly energy-wasteful lifestyle requiring a great deal of food. By contrast, reptiles need only eat once a day or even less often.
"The payoff, however, may be that mammals are much more resistant to soil and plant-borne fungal pathogens than are reptiles and other cold-blooded vertebrates," said Dr. Casadevall.
This stronger immunity to fungi could explain why mammals rose to dominance after the dinosaur extinction event 65 million years ago. Indeed, the fungal bloom that occurred then may be one reason for the extinction of dinosaurs, a possibility outlined in a 2004 Fungal Genetics and Biology paper from Dr. Casadevall.
The arctic could potentially alter the Earth’s climate by becoming a possible source of global atmospheric carbon dioxide. The arctic now traps or absorbs up to 25 percent of this gas but climate change could alter that amount, according to a study published in the November issue of Ecological Monographs.
In their review paper, David McGuire of the U.S. Geological Survey and the University of Alaska at Fairbanks and his colleagues show that the Arctic has been a carbon sink since the end of the last Ice Age, which has recently accounted for between zero and 25 percent, or up to about 800 million metric tons, of the global carbon sink. On average, says McGuire, the Arctic accounts for 10-15 percent of the Earth’s carbon sink. But the rapid rate of climate change in the Arctic – about twice that of lower latitudes – could eliminate the sink and instead, possibly make the Arctic a source of carbon dioxide.
“This study is another example of the important role played by USGS and its partners in providing the scientific research that must be the backbone of any actions related to climate change,” said Secretary of the Interior Ken Salazar.
Carbon generally enters the oceans and land masses of the Arctic from the atmosphere and largely accumulates in permafrost, the frozen layer of soil underneath the land’s surface. Unlike active soils, permafrost does not decompose its carbon; thus, the carbon becomes trapped in the frozen soil. Cold conditions at the surface have also slowed the rate of organic matter decomposition, McGuire says, allowing Arctic carbon accumulation to exceed its release.
But recent warming trends could change this balance. Warmer temperatures can accelerate the rate of surface organic matter decomposition, releasing more carbon dioxide into the atmosphere. Of greater concern, says McGuire, is that the permafrost has begun to thaw, exposing previously frozen soil to decomposition and erosion. These changes could reverse the historical role of the Arctic as a sink for carbon dioxide.
“In the short term, warming temperatures could release more Arctic carbon to the atmosphere,” says McGuire. “And with permafrost thawing, there will be more available carbon to release.”
On the scale of a few decades, the thawing permafrost could also result in a more waterlogged Arctic, says McGuire, a situation that could encourage the activity of methane-producing organisms. Currently, the Arctic is a substantial source of methane to the atmosphere: as much as 50 million metric tons of methane are released per year, in comparison to the 400 million metric tons of carbon dioxide the Arctic stores yearly. But methane is a very potent greenhouse gas – about 23 times more effective at trapping heat than carbon dioxide on a 100-year time scale. If the release of Arctic methane accelerates, global warming could increase at much faster rates.
“We don’t understand methane very well, and its releases to the atmosphere are more episodic than the exchanges of carbon dioxide with the atmosphere,” says McGuire. “It’s important to pay attention to methane dynamics because of methane’s substantial potential to accelerate global warming.”
But uncertainties still abound about the response of the Arctic system to climate change. For example, the authors write, global warming may produce longer growing seasons that promote plant photosynthesis, which removes carbon dioxide from the atmosphere. Also, the expansion of shrubs in tundra and the movement of treeline northward could sequester more carbon in vegetation. However, increasingly dry conditions may counteract and overcome these effects. Similarly, dry conditions can lead to increased fire prevalence, releasing even more carbon.
McGuire contends that only specific regional studies can determine which areas are likely to experience changes in response to climate change.
“If the response of the arctic carbon cycle to climate change results in substantial net releases of greenhouse gases, this could compromise proposed mitigation efforts for controlling the carbon cycle,” he says.
(Photo: A. David McGuire, USGS)
U.S. Geological Survey
An innovative diagnostic technique invented by a Monash University researcher could dramatically fast-track the detection of mental and neurological illnesses.
Monash biomedical engineer Brian Lithgow has developed electrovestibulography which is something akin to an 'ECG for the mind'. Patterns of electrical activity in the brain's vestibular (or balance) system are measured against distinct response patterns found in depression, schizophrenia and other Central Nervous System (CNS) disorders.
The vestibular system is closely connected to the primitive regions of the brain that relate to emotions and behaviour, so Lithgow saw the diagnostic potential of measuring and comparing different patterns of electrovestibular activity.
Working with psychiatry researchers at Monash University's Alfred Psychiatry Research Centre (MAPrc) in Melbourne, Australia, he tested volunteers and found distinct response patterns, or "biomarkers", that distinguished different CNS diseases from each other and from regular electrovestibular activity.
Monash has teamed up with corporate partner Neural Diagnostics to develop and patent electrovestibulography, or EVestG™. It is hoped the simple, quick and inexpensive screening process for CNS diseases will eventually become standard practice in hospitals around the world.
"The patient sits in a specially designed tilt chair that triggers electrical responses in their balance system. A gel-tipped electrode placed in the individual's ear canal silences interfering noise so that these meaningful electrical responses are captured and recorded," the Monash researcher said. "The responses are then compared to the distinct biomarkers indicative of particular CNS disorders, allowing diagnosis to be made in under an hour."
Neural Diagnostics CEO Dr Roger Edwards said the implications of the new technique were huge.
"This could be one of the most significant inventions ever to come out of Monash. CNS disorders cost upwards of $US2 trillion globally and affect one in four people sometime in their lifetime. At present, diagnosing these conditions is done almost exclusively by qualitative measures, through questions and interviews, and it can take many years for sufferers to be correctly diagnosed," Dr Edwards said.
The technique is already attracting international interest and, if further testing goes to plan, it could be adopted in Australian and overseas hospitals within a few years.
"We are doing the necessary research and development and getting independent expert reports done, but results so far are cause for great optimism," Dr Edwards said.
MAPrc Director Professor Jayashri Kulkarni said, "Engineering and psychiatry are two disciplines that do not usually work together, but here at MAPrc, through our collaboration, we are at the forefront of translating biotechnology into clinical tools for psychiatric practice. While there is more work to be done, electrovestibulography could provide a major breakthrough in the diagnosis of mental illnesses".
(Photo: Monash U.)
"Flies have the ability to learn, but the circuits that instruct memory formation were unknown," said Gero Miesenböck of the University of Oxford. "We were able to pin the essential component down to 12 cells. It's really remarkable resolution." Those dozen cells are sufficient to manage what is a difficult cognitive problem: learning to associate a particular odor with something bad, like an electric shock. In essence, these cells create memories that the fly then uses to avoid that odor.
To pinpoint the exact neurons responsible for this memory among thousands in the fly brain, the researchers used a clever technique they developed, called optogenetics, in which a simple flash of light is used to release caged-molecules present in selective neurons that then stimulate the activity of those neurons. An analogous situation, says Miesenböck, is if you wanted to send a message only to certain inhabitants of a city, you would give those you wanted to reach a radio tuned to the right frequency and send the message publicly, over the airwaves.
Miesenböck said his team made some educated guesses about the parts of the brain that would be important for the flies' learning task. From there, they were able to narrow it down through experimentation to the 12-neuron brain circuit. Remarkably, stimulating just these neurons gives the flies a memory of an unpleasant event that never occurred.
"We like to take seemingly lofty psychological phenomena and reduce them to mechanics, to see for example how the intelligence needed to adapt to a changing environment can be reduced to physical interactions between cells and molecules," he said. "The question is: how do you get intelligence from parts that are unintelligent?"
Using their approach to "write directly to memory," scientists can now obtain a level of evidence about brain function that was impossible before, Miesenböck emphasized. He notes that neuroscience for a long time depended primarily on recording neural activity and attempting to correlate it to perceptions, actions, and cognition. "It's more powerful to seize control of the relevant brain circuits and produce these states directly," he says.
Miesenböck adds that the simple brain of a fly likely can tell us much about how more complex brains work. "As a general rule, biology tends to be conservative," he said. "It's rare that evolution 'invents' the same process several times." And, he says, even simple organisms may turn out to have a "surprisingly rich mental life."