Chimps Belong on Human Branch of Family Tree, Study Says
Posted: Friday, May 14, 2004
Source: University Of Rochester
Impact At Bedout: 'Smoking Gun' Of Giant Collision That Nearly Ended Life On Earth Is Identified
Evidence is mounting that 251 million years ago, long before the dinosaurs dominated the Earth, a meteor the size of Mount Everest smashed into what is now northern Australia, heaving rock halfway around the globe, triggering mass volcanic eruptions, and wiping out all but about ten percent of the species on the planet. The "Great Dying," as it's called, was by far the most cataclysmic extinction event in Earth's history, yet scientists have been unable to finger a culprit as they have with the dinosaur extinction. A new paper published in Science, however, claims to identify the crater made by that meteor, and it builds upon an ongoing body of evidence by researchers at the University of Rochester and the University of California at Santa Barbara (UCSB), that points the finger for the Great Dying squarely at the heavens.
"This is very likely the impact site we've been looking for," says Robert Poreda, professor of earth and environmental sciences at the University of Rochester. "For years we've been observing evidence that a meteor or comet hit the southern hemisphere 251 million years ago, and this structure matches everything we've been expecting."
In 2001, Poreda and Luann Becker, research scientist in geological sciences at UCSB, announced that they had detected in 251-million-year-old strata, specific isotopes of helium and argon trapped inside buckyballs--a cage-like formation of carbon atoms--that could only have come from space. Since they were laid down in this same strata around much of the globe, the implication was that a giant meteor had struck the Earth, vaporized, and settled around the southern hemisphere. This past November, the same three authors--Poreda, Becker, and Asish Basu, professor of earth and environmental sciences at the University of Rochester--published another article in Science that found actual pieces of the meteorite that struck the Earth in the same global strata.
Many experts scoffed at the idea of a giant meteor causing the mass extinction between the Permian and Triassic periods, but Poreda points out that many also scoffed at the idea that a meteor was responsible for a later and lesser extinction at the Cretaceous/Tertiary boundary that marks the end of the dinosaurs. Now, the impact theory is largely accepted.
The team knew that the chances of finding the crater, even one from an impact large enough to nearly wipe out life on Earth, would be difficult because the majority of the Earth is covered by ocean. Had the meteor struck there, its telltale crater would have long ago disappeared. As luck would have it, an oil-drilling exploration team in 1970 found a "dome" in the area of Bedout, just off the northwestern coast of Australia. Now covered by 2 miles of sediment, this area was most likely dry land 251 million years ago. Frequently, such domes herald large oil deposits, but in this case the drilling team found only what it labeled as "volcanic rock." The core samples were shelved and forgotten for 25 years, until in 1995 a report in a journal aimed at the oil industry mentioned that the rock might have been formed from a meteor impact.
It wasn't until Becker caught wind of the "volcanic" find in 251 million year old rock that the team members began to think they'd found their smoking gun. Poreda and Becker investigated the core samples first hand. "They were unlike any volcanic rocks I've ever seen," says Poreda. "In a volcanic explosion you may find angular pieces of rock that are broken apart mixed with the volcanic melt. In these samples, though, the rocks were shock melted from an impact.. We left convinced Bedout was our crater."
The clincher was the presence of a feldspar glass in the shape of a feldspar crystal. Such features do not form in volcanic eruptions. Many of the plagioclase samples showed evidence of sustaining an intense shock, meaning the meteor likely hit a bed that contained feldspar crystals, shock-melted their interiors, melting their insides the way a microwave oven might bake a potato's inside while leaving the outer areas cool.
"Once we looked at Bedout with the understanding that it was likely a crater, the geophysics just fell into place," says Poreda.
Geophysical analysis shows the rock strata underlying the dome at Bedout is fractured exactly the way the team expected--showing rock strata older than 251 million years old broken apart, with younger rock above laid down without the fractures. Simulations of a six-mile wide rock striking the area suggest a crater rim should be visible about 60 miles from the central dome, and despite the extreme age of the impact site and the rearrangement of continental plates since then, there is evidence of a rim at that distance. The team has plans to explore the geophysical outlay of the region with more scrutiny.
Coincidentally, the Bedout crater, at 120 miles across, is almost exactly the same size as the Chicxulub crater in the Caribbean that has been identified as the impact site of the meteorite that dealt the dinosaurs their death blow. It's likely that the bodies that struck at each site were of the same size and traveling at similar speeds.
Along with both impacts correlating strongly with two of the greatest extinctions in Earth's history, the team has found that massive lava flows in two different parts of the world have similar corrolations. Basu showed that massive lava flows in India date back precisely to the Chicxalub impact, and recently he also reported that similar giant lava flows in Siberia coincide exactly with the Bedout impact.
"There have been five mass extinctions throughout the Earth's history," says Poreda. "Now we have very strong evidence that massive meteor impacts happened precisely at two of those extinctions."
The research was funded by NASA and the National Science Foundation.
The research is published on Science's pre-print express web site, http://www.sciencexpress.org/
The original news release can be found here
Send page by E-Mail The Universe Seems To Be Older Than Expected
Posted: Friday, May 14, 2004
Source: Istituto Nazionale Di Fisica Nucleare
The Universe, Seen Under The Gran Sasso Mountain, Seems To Be Older Than Expected
Some nuclear fusion reactions inside stars occur more slowly than we thought and, as a consequence, stars themselves, as well as galaxies and the entire universe are a bit older than expected. This is what comes out from the last results of Luna experiment (Laboratory for Underground Nuclear astrophysics), settled by National Laboratories of Gran Sasso and realized in cooperation by Infn and Ruhr University in Bochum (Germany). The study, that will be published on the review Physics Letters B next June 17, has been published today on the website of the review. A second article has been accepted by the review Astronomy and Astrophysics.
Luna's aim is the production of some reactions that occur inside stars, in particular in the Sun, and the measure of their velocity. In Luna, protons (which means hydrogen nuclei) are made collide against nitrogen nuclei: a reaction that leads to the formation of an oxygen nucleus with the contemporary emission of energy. "The great part of the energy emitted by our star derives from fusion reactions of four hydrogen nuclei that lead directly to the formation of a helium nucleus. But there is another process in consequence of that helium nuclei are produced and this process passes through the so-called carbon-nitrogen-oxygen cycle. Cycle velocity is determined by the slowest of the reactions that form it, the one that leads to an oxygen nucleus as a result of the fusion between an azote nucleus and a proton. That is to say the reaction studied by Luna", explains Carlo Broggini, Luna coordinator.
Producing fusion between the nitrogen nucleus and a proton is not difficult itself, but a difficulty lies in obtaining it at the same energy it occurs in stars: a relatively low energy, thanks to which the phenomena is quite slow, corresponding to a very few reactions a day (a lucky case for our planet, because if these phenomena occurred rapidly, the Sun would have burned up its 'fuel' in a few time and this would have made life –as we know it -impossible). "In an ordinary laboratory settled on surface, the effects of the reaction studied by Luna would be totally hidden by similar, but much more abundant effects due to reactions caused by the cosmic rays rain that crashes into our planet without interruption. The Gran Sasso Laboratories are on the contrary located under 1.400 meters of rocks, which constitute an impenetrable barrier for almost all the particles coming from Space. Thanks to these particular conditions we could carry out our experiment", says Carlo Broggini.
The result has been surprising: the carbon–nitrogen –oxygen cycle occurs two times more slowly than expected. "The most fascinating aspect of this study is that another estimate of Universe age flows from it. Actually, the age of the most ancient stars, those that form the so-called globular star clusters, is calculated on the base of the light spectra they emit, supposing we know the carbon–nitrogen–oxygen cycle's velocity As this last one seems to be slower than previewed, the age of the globular star clusters' has also been newly calculated and grown-up of about one billion years. As a consequence, in the light of Luna's new data, the age of our Universe passes from the previous estimate of about 13 billions years to that of about 14 billions years" explains Eugenio Coccia, director of Gran Sasso National Laboratories.
Luna's results offer also another information: neutrinos provided with high energy produced by carbon – nitrogen – oxygen cycle are the half part of what expected, because this last one is responsible of only the 0,8% of the energy emitted by the Sun (and not the 1,6%, as believed). This data is of great interest for astroparticles physicists engaged in experiments that are specifically focused on neutrinos of relatively high energy, as it is for example the experiment Borexino, which is in preparation at Gran Sasso National Laboratories, or the Japanese Kamland.
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