Col. Gen. Vladimir Popovkin, commander of the Russian Military Space Forces, told a news conference Friday that the national satellite network lacked a spacecraft capable of preventing an asteroid strike.

He also said chances of such a collision were infinitely small, and it was inexpedient to spend huge sums on neutralizing this unlikely threat. Still, the general might be underestimating the scale of the asteroid threat.

Over the last few decades there has been a great deal of debate about the level of danger posed by impacts from asteroids and comets. It appears the world needs to take the threat of asteroid strikes a lot more seriously.

Astronomers have already spotted about 800 asteroids, solid rocky celestial bodies, with a diameter of over 1,000 meters (3,250 feet) moving along circumsolar elliptical orbits. However, there may be as a number of as 2,000 large asteroids, and some 135,000 rocks with a diameter of 100 meters (325 feet) and more.

It should be noted that asteroid orbits are unstable and tend to change under the influence of gravitational fields of the terrestrial planets - Mercury, Venus, Earth and Mars.

An asteroid, which flashed past our planet at a distance of 5 million kilometers (3.1 million miles) in November 1996, returned in September 2004 and flew by just 1.5 million kilometers (930,000 miles) from Earth's surface. In March 1989, a 300 meter (975 foot) asteroid crossed the terrestrial orbit and missed the Earth by just six hours. Astronomers spotted the rock only when it was receding into space.

An asteroid measuring over 1,000 meters in diameter is potentially capable of destroying human civilization. Chances of a major asteroid impact in the 21st century are a mere 0.0002 percent, eventhough there is a 2 percent probability of Earth colliding with a 100 meter asteroid before the year 2100.

The blast would equal to 100 Megatons in trinitrotoluol equivalent, and it would kill millions of people if it hit a populous industrial region harboring a number of hazardous enterprises.



Posted by: Edwin    Source