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Posted on 04/02/2006 2:13:59 PM PDT by SunkenCiv
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Supernova 'smoking gun' linked to mass extinctionsLuckily for us, the astronomers say, there is very little danger of it happening again anytime soon... The cluster, called the Scorpius-Centaurus OB association, is now positioned a safe 350 light-years from Earth. But the group says it passed within 130 light-years of Earth about two million years ago. This puts it in the right place at the right time to explain evidence uncovered on Earth by German researchers in 1999. They found atoms of a very rare isotope of iron, 60Fe, in cores taken from the ocean floor. 60Fe is rare in the solar system because it has a half-life of 1.5 million years.
by Eugenie Samuel
Star Material Discovered In South PacificInterstellar matter formed in a supernova has been discovered on Earth now for the first time. Light coming to Earth from distant supernovas is recorded all the time. Likewise, a dozen or so neutrinos from nearby Supernova 1987A have been detected. But atoms from supernovas are a different matter. In a sense, all the heavy atoms on Earth have been processed through or created in supernovas long ago and far away. But now comes evidence of atoms from a supernova that may have been deposited here only a few million years ago. An interdisciplinary team of German scientists from the Technical University of Munich (Gunther Korschinek, 011-49-89-289-14257, firstname.lastname@example.org), the Max-Planck Institute (Garching), and the University of Kiel have identified radioactive iron-60 atoms in an ocean sediment layer from a seafloor site in the South Pacific. First, several sediment layers were dated, and only then were samples scrutinized with accelerator mass spectroscopy, needed to spot the faintly-present iron. The half-life of 60Fe (only 1.5 million years), the levels detected in the sample, and the lack of terrestrial sources point to a relatively nearby and recent supernova as the origin. How recent? Several million years. How close? An estimated 90-180 light years. If the supernova had been any closer than this, it might have had an impact on Earth's climate. The researchers believe traces of the 60Fe layer (like the iridium layer that signaled the coming of a dinosaur-killing meteor 65 million years ago) should be found worldwide but have not yet been able to search for it. (K. Knie et al., Physical Review Letters, 5 July 1999.)
by Phillip F. Schewe and Ben Stein
Physics News Update
July 2, 1999
The drowning waveAny day now, a gargantuan wave could sweep westwards across the Atlantic towards the coast of North America. A mighty wall of water 50 metres high would hit the Caribbean islands, Florida and the rest of the eastern seaboard, surging up to 20 kilometres inland and engulfing everything in its path. If you thought the tsunamis that periodically terrorise the Pacific Ocean were big, consider this: the Atlantic wave will be five times bigger. It will start its journey 6000 kilometres away, when half an island crashes into the sea.
by Tristan MarshallThe Hilina Slump a.k.a. "The Big Crack"A 4,760 cubic mile chunk of the Big Island (Hawaii) is breaking away at the rate of 4 inches per year. This is the Hilina Slump, and it is said to be "the most rapidly moving tract of ground on Earth for its size." The Hilina Slump can move much faster. At 4:48 AM, November 29, 1975, a 37-mile-wide section suddenly dropped 11* feet and slid seaward 26 feet. The result was a magnitude-7.2 quake and a 48-foot-high tsunami. This was a minor of the slump. If the entire 4,760-cubic-mile block decided to break off, it would probably create a magnitude-9 quake and a tsunami 1,000-feet high. All the coast-hugging cities of the Hawaiian Islands would be swept away. And LOOK OUT Australia, Japan, and California.
by Wiliam CorlissLandslideEveryone realised that dropping something the size of New York City into the ocean would kick up a big wave, but it was only when Moore returned to Hawaii to explore the island of Lanai that he realised just how big. On the south side of the island, limestone boulders were scattered, some as much as 100 metres above sea level. Since the island itself is made of volcanic rock, the limestone could only have come from coral reefs beneath the sea surface. Moore also found fields of coral and seashells as high as 120 metres. The piece of mountain that is shifting is much larger than the slide that soaked Lanai. It's more on the scale of the "Nuuanu" collapse that spun the New York-sized chunk of rock off Oahu more than 1 million years ago, says Julia Morgan, a geologist at the University of Hawaii's Manoa campus on Oahu, who has been watching the mountain closely.
by Jonathan Knight
Global Warming Preserved "Mass Kill" Fossils, Study SaysGreg Retallack, geologist at the University of Oregon... says huge releases of carbon dioxide and methane starved the Earth of oxygen, causing mass extinctions over the last 500 million years. He adds that the resulting buildup of billions of dead prehistoric creatures may have acted as a carbon sink, reducing CO2 in the atmosphere and preventing the Earth from becoming as hot and lifeless as Venus... He bases his theory on a compilation of unusually well preserved fossils found around the world, including fish, crustaceans, insects, and other ancient life forms. The fossil record indicates about 40 episodes of exceptional preservation, he says -- episodes that coincide with periods of global warming, when the Earth was low in oxygen... In some mass extinctions, the scientist says, greenhouse gases "ramped up to intolerable levels of more than ten times the modern level of atmospheric carbon dioxide." Volcanic activity and outbursts of undersea gases are the prime suspects for these periods of lethal pollution.
by James Owen
National Geographic News
October 18, 2005
Night Comes to the Cretaceous[W]ith no generally accepted explanation for the dinosaurs' sudden demise, there was no broad, unified defense of an alternative to the Alvarez proposal. Nevertheless, as Powell documents, it was no easy road to acceptance of the idea, especially among paleontologists. One prominent astronomer even argued against the impact hypothesis... Powell finally realizes that the burden of proof has shifted to the anti-impactors... This is a well-written, intelligent book, accessible to the interested layperson but also fully footnoted for geoscientists who want more technical details. It is a thorough account of that portion of the K-T battle, now won, that was fought on a geological turf.
by James Lawrence Powell
reviewed Nov. 24, 1998
by Clark R. Chapman
Night Comes to the Cretaceous
by James Lawrence Powell
Disraeli / Twain: "there are three kinds of lies: lies, damned lies, and statistics."
Table. Chances of dying from selected causes (USA) Cause of death Chances Motor vehicle accident 1 in 100 Homicide 1 in 300 Fire 1 in 800 Firearms accident 1 in 2,500 Electrocution 1 in 5,000 Asteroid/comet impact 1 in 20,000 Passenger aircraft crash 1 in 20,000 Flood 1 in 30,000 Tornado 1 in 60,000 Venomous bite or sting 1 in 100,000 Fireworks accident 1 in 1 million Food poisoning by botulism 1 in 3 million Drinking water with EPA limit of tricholoethylene 1 in 10 million (From C.R. Chapman & D. Morrison, 1994, Nature 367, 33-40.)
Rosetta Stone Decodes Gamma-ray Burst MysteryThis telling March 29 burst in the constellation Leo, one of the brightest and closest on record, reveals for the first time that a gamma-ray burst and a supernova -- the two most energetic explosions known in the Universe -- occur simultaneously, a quick and powerful one-two punch... The team said that the "Rosetta stone" burst also provides a lower limit on how energetic gamma-ray bursts truly are and rules out most theories concerning the origin of "long bursts," lasting longer than two seconds. Gamma-ray bursts temporarily outshine the entire Universe in gamma-ray light, packing the energy of over a million billion suns. Yet these explosions are fleeting -- lasting only seconds to minutes -- and occur randomly from all directions on the sky, making them difficult to study... GRB 030329, named after its detection date, occurred relatively close, approximately 2 billion light years away (at redshift 0.1685). The burst lasted over 30 seconds. ("Short bursts" are less than 2 seconds long.) GRB 030329 is among the 0.2% brightest bursts ever recorded. Its afterglow lingered for weeks in lower-energy X-ray and visible light.
by Bill Steigerwald
NASA Goddard Space Flight Center
Ancient Impact Turned Part of Earth Inside-OutA space rock the size of a large mountain hit 1.8 billion years ago and dredged up part of Earth's lower crust... The evidence comes from a crater in Sudbury, Ontario. Most of the crater was long ago folded into the planet or eroded away. But a section is exposed, revealing minerals and other features that can be compared to more recent craters that are more intact. From all this, scientists gleaned clues to the catastrophic impact. It appears an asteroid about 6 miles (10 kilometers) wide hit the planet at more than 89,000 mph (40 kilometers per second)... Mungall explained that in the top layers of the Sudbury structure, his team found relatively high concentrations of iron, nickel and platinum, stuff that is more common in the lower crust of the planet than in the upper crust (the elements exist in just trace amounts in both regions)... The top layers were also relatively depleted of zirconium, uranium and other elements that tend to show up in other impact sites that only involved melting of the upper crust... Mungall's team also found an enrichment of iridium in the overlying layer at the Sudbury complex, which was already thought to be part of an impact crater.
by Robert Roy Britt
4 June 2004
More asteroids caught in Trojan force trapsThe asteroid belt between Mars and Jupiter may not be alone in harbouring debris left over from the formation of the planets. New calculations hint there could be similar asteroid hoards associated with planets nearer the Sun. This lends added urgency to scientists' eager scrutiny of the belt once regarded as the trash heap of the solar system, now deemed a potential source of rare minerals or of bodies on a collision course with Earth.
by Philip Ball
'Shocking' Experiment Reveals How Asteroids ExplodeWhen watery asteroids are shocked at the surface by an impact -- something that happens to all space rocks several times during their histories -- dust explodes into space. When a dry asteroid is hit by a another rock, not much happens, dustwise. "As a result of these differences in shock response, watery material would become the predominant kind of dust particles produced by mutual collisions of asteroids, Tomeoka said, adding that larger watery fragments would not be abundant.
Thu May 1, 9:49 AM ET
by Robert Roy Britt
The Earth may have been smooth as a cue ball though:
He and his colleagues point to evidence showing that, 3.5 billion years ago, Earth was mostly covered with water.This very early impact wasn't the last:
In addition to the 3.47-billion-year-old impact, Lowe and Byerly have found evidence of meteorite collisions in three younger rock layers in the South African formation. According to Lowe, the force of those collisions may have been powerful enough to cause the cracks -- or tectonic plates -- that riddle the Earth's crust today.The cracks (not plates) have extraterrestrial causes, and are not due to continental drift.
He also pointed to uncertainty among scientists about what the climate of the Archean Earth was really like. In a forthcoming study, Lowe will present evidence that the average temperature of the planet back then was very hot -- perhaps 185 F (85 C).
Physics News Update Number 16 (Story #2)The far side of the Moon, impossible to see from the Earth, was recently photographed by the Galileo spacecraft on its way toward Jupiter. New information about the mineralogical composition of the far side's crust was recorded and pictures revealed the largest impact basin yet seen on the moon, more than 2000 km in diameter and so deep that is may have penetrated through the crust to the moon's mantle. (Eos, January 1, 1991.)
by Phillip F. Schewe and Ben Stein
January 10, 1991
Zoom in on Mars:A new image from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) reveal the ridges to be part of a larger circular structure that's about 53 miles (86 kilometers) across. "It is possible that this pattern reflects an origin related to an ancient, eroded meteor impact crater that was filled-in, buried, then partially exhumed," according to scientists at Malin Space Science Systems, which operates the camera for NASA. "In this case, the ridges might be the remains of filled-in fractures in the bedrock into which the crater formed, or filled-in cracks within the material that filled the crater. Or both explanations could be wrong."
New Highly Detailed Images
by Robert Roy Britt
15 October 2002Ghosts of Impacts Past:Images obtained by SPACE.com reveal hints of circular outlines and subtle depressions that appear to be craters created during tremendous asteroid or comet impacts that pummeled the Red Planets original crust 4 billion years ago or more. The features have since been mostly buried or eroded away... If the entombed craters exist as suspected, then the current visible surface of Mars does not represent the original crust, as some scientists have thought... Mars, Earth and the other planets are thought to have formed about 4.5 or 4.6 billion years ago. A period of heavy bombardment likely ensued, as countless rocks were cleared from the fledgling solar system. A record of the bombardment remains on the Moon, where little erosion or geologic activity takes place... "Erin's results show that the assumption many people have made that the oldest visible surface units go back to 4.6 billion years ago is wrong," the father told SPACE.com. "That means the absolute time scales people have tried to use are probably wrong. It also means there is a recoverable history on Mars that we cannot easily see, except in terms of the crater record. The surface we see is not the original crust of Mars, but something younger."
Ancient Hidden Craters on Mars Revealed
by Robert Roy Britt
05 November 2002
Hydrogen In The Core:Once a magma ocean was formed due to the blanketing effect of an impact-induced steam atmosphere of hundreds of bars, it absorbs most of H2O in the accreting planetesimals. Then the hydrogen is partitioned between the silicate melt and the molten iron that is sinking through the magma ocean to form the core. Thus, hydrogen is partitioned between the atmosphere, magma ocean and core... Two types of the protoatmospheres were proposed to produce the magma ocean: the primary atmosphere consists of the solar nebula gas, and the secondary atmosphere consists of the impact-degassed volatile... atmospheric hydrogen was oxidized by FeO in the magma ocean at its surface, transported through the magma ocean as H2O, and reduced by metallic iron in the deeper part of the magma ocean to form the iron-hydrogen alloy... On the other hand, if the magma ocean was formed through the blanketing effect of the impact-induced steam atmosphere, the hydrogen incorporation into molten iron may have decreased the mass and optical thickness of the atmosphere, and weakened the blanketing effect, because there was no nebula gas that supplies hydrogen to the atmosphere.
An Evidence For The State Of Lost Protoatmosphere
T. Okuchi, Y. Abe and H. Iwamori
Earth in the BalanceGregory Jenkins, a meteorologist at Pennsylvania State University [writes that] 3.8 million to 2.5 billion years ago, its surface was warm enough for life even though the young sun was much fainter than it is today. Jenkins found he could explain the balmy temperatures if Earth had been rotating sideways at the time. Recently, geologists have found evidence of glaciers at Earth's equator between 800 million and 540 million years ago. When Jenkins modeled what the climate would have been like during that time if Earth's axis were tilted at a steep, 70-degree angle, ice appeared at the equator.
by Jessica Gorman
DISCOVER Vol. 21 No. 4 (April 2000)
According to the theory, Earth remained off kilter until around the beginning of the Cambrian Period, 540 million years ago, when a buildup of continents near the south pole flipped our planet to its present 23-degree tilt. The switch to a less extreme climate could explain the remarkable diversification of life at that time. "This is radically different than what most of us think about Earth," Jenkins says.Earth's Core Spins Independently Of The Rest Of The PlanetColumbia scientists Xiadong Song and Paul Richards have combined computer simulations with measurements of seismic waves traveling through the Earth to deduce the rotational behavior of the planet's deep interior. What they find is that the solid inner core---which might consist of a single immense crystal of iron 2400 km across---rotates slightly faster than the rest of the world. The tiny differential spin amounts to about one degree a year. This means that the equator of the inner core swivels past the inside of the outer core at a rate of tens of km per year, 100,000 times faster than the fastest tectonic plates move past each other up near the Earth's surface. A better understanding of how the core gimbals about would in turn provide insights into the nature of Earth's magnetic field, which has reversed itself many times over geological time. (Nature, 18 July 1996.)
by Phillip F. Schewe and Ben Stein
Physics News Update
Number 280 (Story #1), July 22, 1996
Geesh Louise! By the time I got through reading all this data the earth will have wobbled and it won't make any difference anymore.
Not easy to spot, doesn't understand why it happens, but this help explains irregular intervals. Uh-huh, yeah, right.Earth's Changing Orbit Explains Ice Ages[V]ariations in the Earth's orbit around the Sun could explain why ice ages, which occur about every 100,000 years, have not been more regular... Jose Rial, a professor of geophysics at the University of North Carolina at Chapel Hill... looked at isotopes, or variants, of oxygen found by drilling into the sea floor. Such "heavy" oxygen is found more commonly when it is cold. Rial found evidence of both the 100,000 and 413,000 year cycles, but said they were not so easy to spot because the two "interfered" with each other in much the same way that interfering with radio waves -- a process known as modulation -- allows broadcasters to send information in the form of sound. He said the pattern looked like an FM (frequency modulated) radio wave. He does not know the physical mechanism behind this but says it helps explain why the ice ages seemed to occur at irregular intervals.
7.49 a.m. ET (1149 GMT) July 23, 1999
Earth throws a wobblyThe Chandler Wobble, a mysterious wobble that shakes the Earth as it spins on its axis, was first detected in 1891 by an American astronomer called Seth Carlo Chandler. The force of the wobble is such that it is capable of moving the North Pole about six metres (20 feet) from where it should be and lasts around 433 days, or just 1.2 years. Scientists originally calculated that this phenomenon should naturally run out of steam after 68 years unless some force keeps activating it. And this is precisely what appears to happen. NASA's Richard Gross says the principle causes of the wobble are fluctuating pressures on the bottom of the oceans, the result of changes in temperature, salinity and wind patterns. Dr Michael Tsimplis, from the Southampton Oceanography Centre, UK, says that the Gross theory is plausible. "Any stress you apply to the surface of the Earth can affect its axis," he said.
Tuesday, 18 July, 2000
web archive version
Ancient Earth Had Magnetic FieldJohn Tarduno decided to see if he could use the University's Superconducting Quantum Interference Device (nicknamed "SQUID"), a device normally used in computing chip design, which is extremely sensitive to the tiniest magnetic fields. Tarduno's team took samples from a 1955 lava flow in Hawaii and tried to determine if the paleointensity reading would match the actual Earth's magnetic field strength in 1955. It did. With the method tested, it was time for Tarduno to see what it revealed about the magnetic field back in the days of the dinos. His team took dozens of samples from lava flows in India that were nearly 100 million years old-an unusual time in Earth's history when the field was not reversing-and found that the intensity of the field was three times stronger than the old method suggested.
3x Stronger Than Once Thought
by Jonathan Sherwood
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