Outside View: Defending Earth -- Part 1

MOSCOW, Oct. 30 (UPI) -- Anatoly Perminov, the Russian Space Agency chief, announced at a recent news conference that there were plans to develop a space system that could protect the Earth from a potential asteroid impact by 2040.

Members of the scientific community are unanimous in that the asteroid danger is real and that some measures should be taken to prevent it. The discovery of Apophis three years ago made them and the general public even more aware of that threat.

Apophis will pass exceptionally close to the Earth in 2029, only 24,000 miles away, which is where we have most of our communications satellites. Terrestrial gravity might cause this asteroid to leave its trajectory and collide with the Earth in 2036.

The consequences of such an impact would be much more dramatic than the fallout of the Tunguska event, the meteoroid-caused explosion near the Tunguska River in Siberia less than a hundred years ago. Yet the scale of the potential damage would be local rather than global, with Apophis measuring only 1,100 feet in diameter. A global disaster can only be caused by an asteroid as large as 3,300 feet across or more.

As far as collisions with space rocks are concerned, the Earth has, in fact, been more fortunate than other planets. Its close neighbors Mars and Mercury have their surfaces riddled with craters.

The Earth's atmosphere and Jupiter bearing the brunt of some of the heaviest impacts, along with other factors, contribute to our planet's being the solar system's only planet capable of sustaining life. But it has been hit by large celestial bodies many times before, so there are no guarantees it will remain habitable forever.

The diameter of a relatively new crater formed just 50,000 years ago in what is now Arizona is about 0.9 miles.

The Canadian province of Quebec has two craters presumably left by a meteoroid that split apart in midair: one is 19.2 miles across and the other is 13.2 miles.

The 102-mile crater on the Yucatan Peninsula, which became the Gulf of Mexico, is the result of an impact believed to have been produced by an asteroid some 65 million years ago. A similar strike today would kill the entire human race, destroying almost all biological links.

The Earth has narrowly escaped being struck by asteroids countless times. The chance of a large asteroid impact is a realistic one. Astronomers say this is a question of "when" rather than "if."

It used to be believed that impacts like the Tunguska event happen every 700 to 900 years. Today scientists contend that such events could occur much more frequently, as often as once every century. This is because the Earth is now followed by a tail of large celestial bodies. More asteroids have been sighted in the past decade than in the two preceding centuries.

Scientists suggest monitoring all space objects that fly in dangerous proximity to the Earth. This will require 200-inch telescopes, with three or four mounted in each hemisphere. The telescopes will target some particular segment of outer space, and data collected with their help could then form the foundation of a catalog of asteroids measuring more than 3,300 feet across.

Installed on board a spacecraft, telescopes with a mirror 8-12 inches in diameter could monitor asteroids measuring 150 to 300 feet across at a distance of several million miles from the Earth. The main objective of such monitoring will be to follow the trajectory of objects that may have a potential impact on the Earth.

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(Next: How to stop asteroid impacts)

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(Yury Zaitsev is an expert with the Russian Institute for Space Research. This article is reprinted by permission of RIA Novosti. The opinions expressed in this article are the author's and do not necessarily represent those of RIA Novosti.)

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(United Press International's "Outside View" commentaries are written by outside contributors who specialize in a variety of important issues. The views expressed do not necessarily reflect those of United Press International. In the interests of creating an open forum, original submissions are invited.)