[FPSPACE] FW: NEO News (07/24/07) The Economist on NEOs

[LARRY KLAES]

>From: David Morrison <dmorrison at arc.nasa.gov>
>To: David Morrison <dmorrison at arc.nasa.gov>
>Subject: NEO News (07/24/07) The Economist on NEOs
>Date: Tue, 24 Jul 2007 10:08:05 -0700
>
>NEO News (07/24/07) The Economist on NEOs
>
>THE THREAT FROM OUTER SPACE:
>THE ULTIMATE ENVIRONMENTAL CATASTROPHE
>
>Jul 23rd 2007
>From Economist.com
>
>ONE of the main weaknesses of the environmental movement has been its 
>unfortunate predilection for using doom-laden language and catastrophic 
>superlatives to describe problems that are serious but not immediately 
>disastrous. But one calamity that truly deserves such a description is 
>almost never talked about. There are tens of millions of asteroids in the 
>solar system, and several thousand move in orbits that take them close to 
>Earth. Sooner or later, one of them is going to hit it.
>
>Several have done so in the past. Earth's active surface and enthusiastic 
>weather conspire to scrub the tell-tale impact craters from the planet's 
>surface relatively quickly, but the pockmarked surface of the moon-where 
>such scars endure for much longer-testifies to the amount of rubble 
>floating in the solar system. Earth's thick atmosphere makes it better 
>protected than the moon: asteroids smaller than about 35 metres (115 feet) 
>across will burn up before hitting its surface. Nevertheless, plenty of 
>craters exist. The Earth Impact Database in Canada lists more than 170.
>
>Fortunately, such impacts are relatively rare, at least on human 
>timescales. Statisticians calculate that the risk to lives and property 
>posed by meteorite strikes are roughly comparable with those posed by 
>earthquakes.
>
>Although the chance of an impact may be small in any given year, the 
>consequences could be enormous. The effect of an impact depends on an 
>object's size and speed. A meteorite a few metres wide could level a city. 
>The largest (a kilometre or more in diameter) could wreak ecological havoc 
>across the entire globe. David Morrison, a NASA scientist, argued at a 
>recent conference that a large meteorite strike is the only known disaster 
>(except perhaps global nuclear war) that could put civilisation at risk.
>
>Examples give a more visceral illustration than statistics. The Chicxulub 
>crater, buried beneath modern Mexico, is 65m years old and 180km (112 
>miles) across. Some think that the ten-kilometre meteorite that created it 
>threw so much dust into the atmosphere that it blotted out the sun and led 
>to the extinction of the dinosaurs. In 1908 a comparatively tiny piece of 
>space-borne rock, 30-50 metres across, exploded above Tunguska, a remote 
>part of Siberia. The blast-hundreds of times more powerful than the atom 
>bomb dropped on Hiroshima 37 years later-felled 80m trees over 2,150 square 
>kilometres. Only blind luck ensured that it took place in a relatively 
>unpopulated part of the world. Astronomers are currently trying to work out 
>whether a 270-metre asteroid named 99942 Apophis will hit Earth in 2036 
>(probably not, but it would be nice to be sure).
>
>Happily for humanity, technology has advanced to the point where it is 
>possible, in principle, to avoid such a collision. In 1998 NASA agreed to 
>try to find and catalogue, by 2008, 90% of those asteroids bigger than 1km 
>in diameter that might pose a threat to Earth. Any deemed dangerous would 
>have to be pushed into a safer orbit. One obvious way to do this is with 
>nuclear weapons, a method that has the pleasing symmetry of using one 
>potential catastrophe to avert another. But scientists counsel caution. A 
>nuclear blast could simply split one large asteroid into several smaller 
>ones, some of which could still be on a collision course.
>
>Other plans have been suggested. One is to use a high-speed spaceship 
>simply to ram the asteroid out of the way; another is to land a craft on 
>the rock's surface and use its engines to manoeuvre the asteroid to safety. 
>A subtler method is to park a spaceship nearby and use its tiny gravity to 
>pull the asteroid gradually off course. For now, all such suggestions are 
>theoretical, although the European Space Agency is planning a mission, 
>named Don Quijote, to test the ramming tactic in 2011.
>
>These schemes offer consolation, but any effort to deflect an asteroid 
>requires plenty of advance warning, and that may not always be available. 
>NASA has so far catalogued only the very largest, "civilisation-killing" 
>asteroids. Plenty of smaller ones remain undiscovered, and they could 
>inflict considerable damage. In 2002 a mid-sized asteroid (50-120 metres 
>across) missed Earth by 121,000km-one-third of the distance to the moon. 
>Astronomers discovered it three days after the event. Comets, which 
>originate from the outer reaches of the solar system, are faster moving and 
>harder to track than asteroids, but carry just as much potential for 
>catastrophe.
>
>But perhaps the biggest problem is humanity's indifference. Currently only 
>America is spending any money on detection, and even there, politicians 
>have other priorities. Much of the work is done by Cornell University's 
>Arecibo radar in Puerto Rico, which is facing federal funding cuts. The 
>telescope costs roughly $1m a year to operate. As an insurance policy for 
>civilisation, the price looks cheap.
>
>--
>+++++++++++++++++++++++++++++++++++++++++++
>
>NEO News (now in its thirteenth year of distribution) is an informal 
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