Asteroid Collisions: Estimating the Danger By Robert Roy Britt Senior Science Writer posted: 01:41 pm ET 03 November 1999 An asteroid capable of global disaster would have to be more than a quarter-mile wide. It would rock the planet with earthquakes and volcanoes and raise a cloud of dust that would darken the skies for months, destroying agriculture and, possibly, many species of plants and animals. Asteroids that large strike Earth only once every 1,000 centuries on average, NASA officials say. Smaller asteroids that are believed to strike Earth every 1,000 to 10,000 years could destroy a city or cause devastating tsunamis. http://www.space.com/scienceastronomy/astronomy/asteroid_danger_991103.html ----------------------------------------------- [note: Oh well, nothing to worry about then? Check below] ----------------------------------------------- http://www.space.com/scienceastronomy/solarsystem/tj_extinction_010511-1.html?Enews=y Fifth Worst Mass Extinction Linked to Asteroid Impact By Robert Roy Britt Senior Science Writer posted: 07:00 am ET 11 May 2001 They call them the Big Five -- a handful of unfathomable mass extinctions over the past 500 million years, each estimated to have obliterated somewhere between 50 and 96 percent of all species on the planet. That much we know, because Earth recorded the mass deaths in layers of ancient soil, where crowds of miniscule corpses and other evidence show wholesale destruction of the smallest critters, on which larger animals depend. What we don't know, except in one case, is what caused these five mass extinctions. Nor is there solid evidence showing how rapidly the catastrophes occurred. Such knowledge would be a window not only to the past, but to the future: How likely is it that future Earth dwellers will meet with an inescapable catastrophic fate, much like the dinosaurs did? And how much time will there be to adjust or perish? While there are no firm answers, a three-page study in the May 11 issue of the journal Science adds modestly to a mounting stack of reports suggesting that asteroids and comets are the leading cause of terrestrial death, delivering immensely fatal blows every 100 million years or so that wipe the slate of life frighteningly close to clean in remarkably rapid fashion. ----------------------------------------------- Researchers review the possible causes of catastrophe and warn that the planet will inevitably be struck by a giant asteroid Special report: natural disasters Tim Radford, science editor Friday September 7, 2001 The Guardian The end of the world really could be at hand, scientists warned yesterday, and there are a number of ways it could happen, the British Association science festival in Glasgow heard yesterday. A 1km wide asteroid could sweep in from the southern skies, hit Australia at 20kms a second and gouge out a crater 10km across, throwing huge lumps of rock into orbit. Forty-five minutes later, blazing fragments of Australia would begin to reduce Britain to ashes. The catastrophe was quite probable in any one year and inevitable in the long run, warned Duncan Steel, an asteroid expert at the University of Salford. Dr Steel was the only non-American in a Nasa committee which reported to US Congress on asteroid impact hazard. His research was used by Hollywood in the films Armageddon and Deep Impact. But asteroid strike was not Hollywood fiction, he said. The demise of the dinosaurs was linked to the impact of a 10km asteroid in Mexico 65m years ago. In 1908, an asteroid about 100m across exploded 6km above the Earth, releasing energy of a thousand Hiroshimas over Tunguska in Siberia. "An object coming in at 20km per second hitting the atmosphere goes kerblam. It needs to be bigger than 100 metres in size to reach the ground intact but that does not mean we are safe. Because if the next Tunguska were to occur above Marble Arch in London, let us say, the whole of London out to the M25 would be flattened," he said. The British government had taken no action on a report from one of its own committees on asteroid hazard. But it paid to watch the skies for asteroids: if spotted years, or better, decades early, they could be averted. It would be delicate work. "Asteroids are piles of rubble held together by their own gravity. You have to deal with them very gently," he said. A nuclear explosion detonated at the distance of a radius - 500 metres in the case of a 1km asteroid - could slow or deflect the monster even if it was due to collide in 20 years. There would be no blast wave in space, but one side of the asteroid would be heated, and start to vaporise. This would have a jetting effect, and could slow the monster by half an inch a second. "It might not sound much, but half an inch over 20 years adds up to greater than the radius of the Earth. It would miss us." Mass which fell to Earth • There are more than 1 million known asteroids, mostly in the asteroid belt between Jupiter and Mars. • More than 1,000 asteroids with Earth-crossing orbits have been spotted. • More that 100 tonnes of cosmic rubble hits the Earth every day. • A 50 metre asteroid hits the Earth's atmosphere about once a century, releasing the equivalent of 10 megatons of TNT in the explosion • A 1km asteroid - 500 are known - hits the Earth every 100,000 years. About 500 may remain undiscovered. • The largest asteroid ever identified on an Earth-crossing orbit was spotted in July. It is 15-20km in size. It will pass the Earth safely next April • Four teams in the US and one in Japan are watching for new asteroids. Most tracking of known asteroids is done by amateur astronomers. • There are no asteroid searchers in the southern hemisphere. There is no funded Spaceguard programme in the UK. Guardian Unlimited © Guardian Newspapers Limited 2001 ----------------------------------------------- http://www.space.com/spacewatch/august_asteroid_020723.html Newfound Asteroid to Pass Near Earth in mid-August By Robert Roy Britt Senior Science Writer posted: 02:00 pm ET 23 July 2002 EXTRACT Asteroid 2002 NY40 was first spotted July 14 with the 1-meter (3 feet) LINEAR telescope in Socorro, New Mexico. Its discovery contrasts with that of another asteroid, 2002 MN, which had an even closer brush with Earth in June but was not detected until three days later, by the same facility. Every few months, typically, an asteroid passing within the Moon's orbit is noticed before or shortly after it makes its closest approach to Earth. ----------------------------------------------- http://news.bbc.co.uk/1/hi/sci/tech/2246449.stm This summer, as India and Pakistan faced-off over the disputed Kashmir region, US early warning satellites detected an explosion in the Earth's atmosphere with an energy of 12 kilotonnes of explosive. The detonation, equivalent to the blast that destroyed Hiroshima, fortunately occurred over the Mediterranean Sea. But according to US Brig Gen Simon Worden, if it had occurred at the same latitude a few hours earlier, the result could have been much worse. "An object probably less than 100 metres in diameter struck Tunguska in Siberia in 1908, releasing the energy equivalent to a 10-megaton nuclear blast," says Worden. "In 1996, our satellite sensors detected a burst over Greenland equal to a 100-kiloton yield. Had any of these struck over a populated area, perhaps hundreds of thousands might have perished" ----------------------------------------------- Perceptions note:- Even over the short time-span of these reports, more realism was developing. Earlier media write-ups were jokes, twenty or thirty years ago the media treated all such calculations with derision - easy to do when ignorant of facts Check those 'statistics': in only two / three years the calculated threat has approximately doubled! We see - more facts reveal more danger ----------------------------------------------- Early extinction http://www.perceptions.couk.com/thumlate.txt Meteor Impact Database http://www.unb.ca/passc/ImpactDatabase/ Terrestrial Impact Craters http://www.solarviews.com/eng/tercrate.htm Reclassification http://www.perceptions.couk.com/uef/thump2.txt Reclassification http://www.perceptions.couk.com/uef/thump3.txt A plea http://www.perceptions.couk.com/uef/complasens.txt Calculate the mega-tonnage odds per year http://www.perceptions.couk.com/chance.txt ----------------------------------------------- Our crowded Solar System http://cfa-www.harvard.edu/iau/lists/OuterPlot.html http://cfa-www.harvard.edu/iau/lists/InnerPlot.html http://cfa-www.harvard.edu/iau/lists/InnerPlot2.html ----------------------------------------------- FURTHER REFERENCES GO - "search perceptions" - in SEARCH-ENGINE file-ID www.perceptions.couk.com/uef/thump.txt