Asteroid That Might Hit Earth Next Century to Be Visited by U of A Spacecraft in 2018

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Near-Earth Objects, or NEOs, have orbits around the sun and are most hazardous to humans. A comet from a distant corner of the solar system could fly in and hit Earth, but that's considered less likely than a strike by an NEO.

Back in the earliest days of the solar system, about half a billion years after the sun began shining and the planets cooled, asteroids pummeled the planet in what's known as the Late Heavy Bombardment.

Renu Malhotra, a U of A professor of planetary sciences, wrote a groundbreaking paper in 1993 suggesting that the bombardment was caused by the "migration" of the outer planets to orbits farther from the sun. A sizable portion of the asteroid belt between Jupiter and Mars fell inward, hitting Earth (among other things) with extra water and organic molecules that are the so-called building blocks of life.

"Asteroids are a double-edge sword," says Malhotra, who's working on how to refine the calculations of their orbits. "They can bring organic material and kick-start life. Then, later on, you can have a big asteroid come and wipe out life."

But not if we can do something about it.

The bright fireball that raced across the Tucson sky on the evening of December 10 won't soon be forgotten by the hundreds of people who saw — and heard — it.

"We felt this absolutely tremendous explosion . . . It shook the windows. It shook everything in the house," Tucson resident Tony Kubrak told a local TV station; his comments were broadcast nationwide by CNN. After hearing the noise, Kubrak said, he went outside: "I see this tremendous white bright light in the western sky."

(It's unclear why Kubrak would hear the noise before seeing the flash, since sound moves much slower than light. He didn't return a call from New Times.)

Some witnesses reported that the meteor looked green; one said it was orange and red.

The size of the object that caused all the fuss, experts say, probably was no bigger than a basketball. No fragments of it were found, though numerous meteorite aficionados combed the desert looking for them.

A fireball, also known as a bolide event if it occurs with a noticeable explosion, is nature's fireworks show. Fireballs stretch far across the night sky and may leave long smoke trails, commanding the attention of those below in their brief life.

The light streaks of meteors and explosions caused by bigger space objects has to do with their great speed. Bennu, for example, is tumbling through space at more than 60,000 miles per hour. In comparison, a bullet from an AK-47 flies at a relative snail's pace, about 1,600 miles per hour. Fortunately, most objects that hit Earth aren't Bennu-size or even as large as the one that hit Chelyabinsk. But a rain of rock always is falling.

The Catalina Sky Survey, a U of A project that began in 1998, finds an average of more than one per night. From one of the project's telescopes in the Catalina Mountains, astronomer Rich Kowalski discovered the first asteroid in 2014 in the first few minutes of New Year's Day, hours before the rock exploded over the Atlantic Ocean.

Not long after reporting its position to the International Astronomical Union Minor Planet Center, other scientists calculated that "2014 AA" would hit the planet. The size of a small car, the object is believed to have gone down between Central America and East Africa. No doubt, it created a huge fireball — but no cruise-ship passenger, airline pilot, or anyone else reported seeing it.

It was only the second discovery ever made of an impacting asteroid. Kowalski, who's also a flight instructor and photographer, made the first one, too. He found a 13-footer in 2008 that exploded over Sudan. It was the first asteroid ever to hit the ground that first had been tracked by telescope.

Funding for asteroid-hunting programs in the United States stood at $4.5 million a year until 2010, says Stephen Larson, the project's co-chief. After 2010, it went up to $10 million annually, and astronomers began looking more intently for asteroids as small as 100 meters across.

"These could be a problem for cities," Larson says.

After Chelyabinsk, NASA upped the funding for asteroid sky surveys to $20 million a year. The average yearly budget for the CSS has been about $1 million a year for the past six years.

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Ray Stern has worked as a newspaper reporter in Arizona for more than two decades. He's won numerous awards for his reporting, including the Arizona Press Club's Don Bolles Award for Investigative Journalism.