It's such a simple idea that it's surprising no one seems to have thought of it before. Did a massive asteroid or comet impact kick-start plate tectonics on Earth?
For much of our planet's history, rocky plates have been sliding over a viscous, molten mantle, colliding to build mountain ranges or spreading apart to make way for oceans. In a neat piece of recycling, an oceanic plate dives, or "subducts", underneath a less dense continental plate, and eventually melts into the hot mantle.
Geologists estimate that plate tectonics began during the Archean period, between 2.5 and 3.8 billion years ago - but they don't know what triggered it. Ancient Earth was too hot for the crust to solidify completely, and the lightest minerals would have floated to the surface over the entire planet, making the subduction of denser plate material unlikely.
Malcolm Moore
TelegraphSat, 08 Dec 2007 16:56 UTC
An ancient Middle-Eastern empire had already mastered the art of biological warfare almost 3,500 years ago, according to an Italian scientist.
Sprites are likely generated by major lightning strikes.Giant red blobs, picket fences, upward branching carrots, and tentacled octopi - these are just a few of the phrases used to describe sprites - spectacular, eerie flashes of colored light high above the tops of powerful thunderstorms that can travel up to 50 miles high in the atmosphere.
Sprites, so-named by a University of Alaska scientist inspired by the creatures in Shakespeare's "The Tempest," have been observed since the 1800s, though rarely visible from the ground. Aircraft pilots began reporting sightings of sprites in the 1950s and '60s, but they were not formally identified until 1989 when the Space Shuttle (STS-34) recorded the flashes as it passed over a thunderstorm in northern Australia. While many theories have been offered on the cause of this rare phenomenon, new NASA-funded research is settling the mystery and helping to determine the driving force behind these marvel displays of light.
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| This dramatic, garishly colored image was captured with a low-light level camera on June 7, 2001. It shows what appears to be a "burning tree", or red sprite, above the National Cheng Kung University campus in Tainan City, Taiwan.
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To truly understand some of the movement we see at the Earth's surface, scientists have to probe deep into the interior. A region near the planet's core, about 1,800 miles down called the core-mantle boundary, is particularly intriguing.
Through novel experiments mimicking high-pressures and temperatures there, scientists at Los Alamos National Laboratory (LANL) and the Carnegie Institution's Geophysical Laboratory* may have solved a longstanding mystery about why certain seismic waves called shear waves move so sluggishly through clumpy patches (ultralow velocity zones) at these incredible depths. The team found that when lots of iron is added to the most prevalent mineral in that region, (post-perovskite) shear waves put on the breaks and move in slow motion. Their discovery offers an alternative to the prevailing idea that these regions are partially melted, and it has important implications for understanding how volcanoes, located in places such as Hawaii and Iceland, may originate. The research is published in the April 28, 2006, Science,
Seismologists learn about the deep Earth, in part, by observing different seismic waves from earthquakes as they travel through the planet. Shear waves wiggle at right angles to the direction of their movement, but they don't move through liquid at all and are thus useful for understanding aspects of the Earth's composition. The team, including the daughter/father duo Wendy Mao (LANL) and Carnegie's Ho-kwang (Dave) Mao, used a novel technique to measure the velocity of shear waves in the lab, through the most abundant mineral in that region called post-perosvkite.
Unlike the circuitry of the visual system, that of the olfactory system was thought to be hardwired: Once the neurons had formed, no amount of sensory input could change their arrangement. Now researchers at Rockefeller University and their collaborators have upturned this scientific dogma by showing that there is a sensitive period during which the external environment can alter a circuit in the fly brain that detects carbon dioxide, a gas that alerts flies to food and mates. This research, to be published in the December 6 issue of
Neuron, may suggest that this brain plasticity isn't limited to the carbon dioxide detection circuit. Rather, it may be a general feature of the olfactory system itself.
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| The plasticity of smell. During the first few days of life, chronic exposure to carbon dioxide (right) rather than air (left) alters the activity of projection neurons and interneurons in the fly brain - research that is first to show that the olfactory system is plastic.
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More than 200 Fish and Wildlife researchers cite cases where conclusions were reversed to weaken protections and favor business, a survey finds.
More than 200 scientists employed by the U.S. Fish and Wildlife Service say they have been directed to alter official findings to lessen protections for plants and animals, a survey released Wednesday says.
The survey of the agency's scientific staff of 1,400 had a 30% response rate and was conducted jointly by the Union of Concerned Scientists and Public Employees for Environmental Responsibility.
A division of the Department of the Interior, the Fish and Wildlife Service is charged with determining which animals and plants should be placed on the endangered species list and designating areas where such species need to be protected.
More than half of the biologists and other researchers who responded to the survey said they knew of cases in which commercial interests, including timber, grazing, development and energy companies, had applied political pressure to reverse scientific conclusions deemed harmful to their business.
Following ground-breaking research showing that neurons in the human brain respond in an abstract manner to particular individuals or objects, University of Leicester researchers have now discovered that, from the firing of this type of neuron, they can tell what a person is actually seeing.
The discoveries of large Earth-like planets outside our Solar System, so-called "super-Earths," has prompted much speculation about just how Earth-like they may be. Recently, scientists from Harvard University suggested that these planets will, like Earth, have plate tectonics.
The government of South Korea is drawing up a code of ethics to prevent human abuse of robots - and vice versa.
The so-called Robot Ethics Charter will cover standards for robotics users and manufacturers, as well as guidelines on ethical standards to be programmed into robots, South Korea's Ministry of Commerce, Industry and Energy announced last week.
