Asteroid detected in a close call with Earth

Thu Jun 20, 4:22 PM ET

By THOMAS WAGNER, Associated Press Writer

LONDON - An asteroid the size of a soccer field narrowly missed the Earth by 75,000 miles (120,000 kms) last week, in the closest known approach by objects of this size in decades, scientists said Thursday.

"In the unlikely event the asteroid had struck Earth in a populated area, it would have caused considerable loss of life," said Grant Stokes, the principal investigator for the Lincoln Laboratory Near Earth Asteroid Research Project, whose New Mexico observatory spotted the object. "The energy release would be of the magnitude of a large nuclear weapon."

Another scientist, Brian Marsden of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, said: "It was a close shave."

Marsden, whose organization gathers information on all such encounters, called it "the only object of this size known to have come closer to the Earth than the moon in decades."

The asteroid, provisionally named 2002 MN, was traveling at more than 23,000 mph (38,000 kph) when it was spotted, Stokes said in a telephone interview. It was not detected until three days after it came close to the Earth on June 14. When such asteroids are detected, they are usually spotted when they are approaching or departing Earth.

With a diameter of between 50 and 120 meters (yards), the asteroid was about the size of a soccer field, which tend to be about 105 meters (yards) by 75 meters (yards), Stokes said. The size of asteroids is estimated by measuring their brightness, without knowing their composition.

Although lightweight compared with some asteroids, 2002 MN was big enough to have caused local devastation similar to the impact of one in Siberia in 1908. On that occasion, an asteroid that exploded above Tunguska flattened 2,000 square kilometers (1,240 miles) of forest. The asteroid's air blast was believed to have done the damage, since no crater was found.

In general, damage on the ground depends on what an asteroid is made of, varying from solid metal to a loosely bound aggregate.

"Looking statistically at the asteroid population, maybe 50 times a year a 100-meter-class asteroid passes within a lunar distance of Earth," Stokes said. "But only a handful of such asteroids that have penetrated the Moon's orbit have been spotted by asteroid search programs."

Dr. Benny Peiser, an expert on near earth objects, or NEOs, at Liverpool John Moore's University in England, said: "Whilst the vast majority of NEOs discovered do not come this close, such near misses do highlight the importance of detecting these objects. This reminder comes in a week when the U.K. telescopes on (the Spanish island of) La Palma are being tested to search for NEOs."

Currently, there is no dedicated program searching for NEOs of 2002 MN's size, and the American space agency NASA ( news - web sites) concentrates its efforts on bodies bigger than one kilometer (.62 of a mile) across.

"NASA has a goal of discovering and obtaining good orbits for all the near earth objects with diameters larger than 1 kilometer," said Thomas Morgan, a scientist at NASA headquarters in Washington. "Asteroids of this size could potentially destroy civilization as we know it."

Asked about the discovery of the smaller 2000 MN asteroid, Stokes said: "We're delighted to have found this object. ... We know objects in this class are not generally detected."

He also said, "It's something the public should know about, but shouldn't get nervous about."

Asteroids of that size are estimated to hit the Earth every 100 to several hundred years, causing local damage, but no disaster to civilization or the planet's ecosystem, Stokes said.

"Civilization has to get used to them on some level," he said, adding that larger ones that NASA is trying to detect and monitor could theoretically hit Earth every million years, or at longer intervals.

-- (doom@getting.closer), June 20, 2002

Answers

A meter and a yard are not equivalent. This article is obscene.

-- David L (bumpkin@dnet.net), June 21, 2002.

If that thing landed on your town I don't think you'd notice the difference.

-- (close enough for horseshoes and elephants @ is close enough. for deadly asteroids), June 21, 2002.

LOL! I can't dispute that.

-- David L (bumpkin@dnet.net), June 21, 2002.

75,000 miles is less than one-third of the distance between us and the moon. In astronomical terms this is way closer than a near miss, it's equivalent to having a bullet miss you while being close enough to singe your hair as it passes.

-- (wheeeew@close.one!), June 21, 2002.

I wonder if there is a weapon under investigation/development that could be used to deflect or destroy such asteroids if they are heading directly for earth.

Oh well, it's probably not a bad way to die.

-- (lars@indy.net), June 21, 2002.

Lars, here's the problem...

"It was not detected until three days after it came close to the Earth on June 14."

Finding objects this small is like the needle in the haystack, but they're still big enough to wipe us out.

I read several years ago that the defense department had been working on a 4ft wide laser beam that could zap objects and satellites in space. Something like that might work, but the point is moot unless they can find the asteroids first.

-- Bill Nye (the@science.guy), June 21, 2002.

Oooops, I misread the story. I thought it said three days before.

We must accelerate research on force fields!

-- (lars@indy.net), June 21, 2002.