News Column

Close, but No Asteroid to Hit Us

Feb 8, 2013

Tom Beal

An asteroid about the size of the one that created Arizona's Meteor Crater will whiz by Earth on Feb. 15, getting closer to us than some of our orbiting communications satellites.

Not to worry.

That's still more than 17,000 miles away, but asteroid 2012 DA14 will set a record for a close approach by an object of its size, estimated at 150 feet in diameter, according to NASA's Near-Earth Object Program.

NASA is treating the near-miss as an educational moment, scheduling a news conference Thursday to discuss how it watches for near-Earth objects, how it might deflect one on a bull's-eye course and what scientific missions it is planning to gather more information about them.

Folks in Indonesia will be able to see the asteroid with a good pair of binoculars, but it won't be visible here.

"Its closest approach is about 12:20 p.m. Tucson time," said Steve Larson, principal investigator of the Catalina Sky Survey, a NASA program based at the University of Arizona's Lunar and Planetary Lab that searches for potentially dangerous objects from observatories on Mount Lemmon and in Australia.

The asteroid will pass from south to north and will be much too far away and faint by the time North America revolves into viewing range, Larson said.

Asteroid 2012 DA14 was first spotted last year by the La Sagra Sky Survey in southern Spain. It is estimated to be about 150 feet across -- hard to spot and beneath the one-kilometer (3,281 feet) threshold set by NASA for civilization-altering impacts.

It's about the same size as the iron asteroid that slammed into Northern Arizona about 50,000 years ago, creating Meteor Crater near present-day Winslow.

The hole that one left is 2.4 miles in circumference and more than 550 feet deep.

Astronomers haven't spectrally analyzed 2012 DA14 and don't know its makeup. Chances are it isn't as heavy as the Meteor Crater rock. Only 3 to 4 percent of asteroids are made of iron, said Ed Beshore, deputy principal investigator on OSIRIS-REx, the UA-led NASA mission to another potentially dangerous asteroid.

"The chances are very good this is stony," said Beshore, who will represent OSIRIS-REx at Thursday's news conference.

A stony asteroid this size would break apart in Earth's atmosphere, creating a fireball and a seismic burst that would cause "regional destruction," Beshore said.

A similar-sized asteroid exploded over a sparsely populated area of Siberia in 1908, Beshore said. Later scientific expeditions estimated it destroyed 80 million trees.

But, to repeat, that's not going to happen with 2012 DA14. Beshore said scientists have "determined its orbit to a very high degree of precision."

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