http://en.rian.ru/science/20080701/112730689.html
Russian expert says nuclear devices can defend against asteroids
Tunguska Event still a mystery 100 years on (Image gallery)
MOSCOW, July 1 (RIA Novosti) - Nuclear explosive devices are the most effective
means of protecting Earth from possible collisions with space bodies, including
comets and asteroids, a Russian nuclear physicist told RIA Novosti on Tuesday.
Scientists around the world have long been seeking means of protecting the
Earth from the threat of dangerous Near Earth Objects (NEOs). Scientists say
such collisions pose a threat on average once every 200-1,000 years.
Vadim Simonenko, deputy head of research at the Russian Federal Nuclear Center
in the Urals town of Snezhinsk, believes that nuclear explosive devices are
more energy efficient, compact and less heavy than lasers or the so-called
"gravitational tractors" in terms of their practical application as "weapons
against NEOs."
"We in Russia have a wealth of experience in the controlled use of nuclear
explosions for peaceful purposes," Simonenko said. "A nuclear device in
skillful hands is like a scalpel in the hands of a surgeon."
The scientist said special nuclear devices must be created for effective use
against NEOs. In order to disperse an asteroid with diameter of up to 100
meters, these devices must have a yield of about one megaton of TNT equivalent,
and weigh several hundred kilograms.
"It is a difficult technical task but it can be accomplished. Besides, there is
no need for actual testing [of these devices] because it may be done through
computer modeling," he said.
Existing nuclear devices, both military and civilian, were created for specific
purposes and do not meet the requirements for "precision strikes" against NEOs,
especially comets, which are less predictable than asteroids, Simonenko said.
An earlier report at a Moscow scientific conference said 99942 Apophis, or
Asteroid 2004 MN4, with a diameter of 350 meters, currently poses biggest space
threat to Earth.
In 2029, this NEO will be at a distance of only 36,000 km (22,400 miles) -
closer than satellites in geostationary orbit. Earth's gravity could alter the
path of Apophis in such a way that it would collide with Earth on its next
approach in 2036.
The explosion could surpass the famous Tunguska explosion of June 30, 1908,
which affected a 2,150 square kilometer (830 sq miles) area of Russia felling
over 80 million trees in the Krasnoyarsk Territory in Siberia.
Some researchers believe, however, that blowing up NEOs in space poses could
result in large fragments surviving the fiery passage through the atmosphere
and still hitting the planet.
They propose a more cautionary approach toward dealing with NEOs, by deflecting
them from their collision path toward the Earth.
"Deflection is the most favorable strategy, but it requires a considerable
early warning period - up to a few years," Simonenko said. "We may not have
such a luxury because small asteroids [100-150 m in diameter] are hard to
detect."
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