The up-close imaging and direct sampling of the small rocks, gravel, and dust (the regolith) on the asteroid's surface will be compared with information already gleaned from Bennu by telescopes. This telescope data will be "ground-truthed" by what minerals are found in the sample, meaning "we've improved our ability to interpret the spectra of asteroids across the solar system," Lauretta says.

Thanks to a 1978 made-for-TV movie called A Fire in the Sky, we more easily can imagine what a comet strike on Phoenix would be like.

A promo clip on YouTube includes a scene of the comet hitting what looks to be lower west side of the city, followed by the destruction of the Hyatt Regency building.

"Phoenix lay gutted and dead under the immense desert sky, all its splendors ruined, all its towers of glass and steel crushed and devastated," reads a passage near the end of the movie's novelization, released the same year.

The likelihood of any particular city getting destroyed by an impact from space is slim. Water covers more than two-thirds of Earth's surface, making an ocean strike a better bet. Yet because a large impact would be so destructive, some experts believe the odds of any one of us dying in a comet strike can be compared to other causes of death.

Estimates vary hugely: One estimate on a Tulane University website gives lower odds of 1 in 3,000 for each person on Earth (making death by drowning less likely) to 1 in 250,000, still far less than death by botulism or shark attack. Last year, the article stated that impact death is a long shot, with 75 million-to-1 odds, though that still beats the chances of winning a Powerball jackpot.

"An impact by an object a kilometer or two in diameter could kill about a billion people and happen once in a million years on average," writes Donald Yeomans in the 2013 book Near-Earth Objects: Finding Them Before They Find Us.

Yeomans, manager of NASA's Near-Earth Object Program Office, believes that a large impact would "have the capacity to reduce large regions of the Earth's surface to ashes and create another extinction event. We cannot afford to play the odds when civilization is at stake."

About 50,000 years ago, the mile-wide Meteor Crater near Winslow was carved out in 10 seconds by a nickel-iron asteroid about 150 feet long, evidence shows. It's impossible for anyone who's seen movies like A Fire in the Sky to stand on its windy rim and not think about how the crater would look in the middle of a city.

Not that long ago, scientists thought strikes like the one that shook Chelyabinsk occur once a century, but new research moves that up to once every 50 years, or less, says Jay Melosh, a former geophysicist and asteroid researcher at the U of A who now works at Purdue (where, among his many tasks, he helped build the aforementioned impact-calculating website).

Though the biggest space rocks present the worst threats, the "most likely" impact scenario may be from these lesser bodies, he believes.

"Expect a very strong airburst, something that breaks windows, maybe kills people on the ground," Melosh says. "The civil-defense thing to do is tell people to get away from the windows."

Melosh doesn't expect a relatively small mass to hit the ocean and cause a tsunami that wreaks havoc on coastal cities, something seen in the 1998 movie Deep Impact. Research by Melosh and others, based on previous underwater-detonation tests by the United States, seems to prove that asteroid-caused tsunami waves would break early and lose their energy.

The scariest impact scenario resembles what caused a 110-mile-wide crater 65 million years ago near what is now Chicxulub, a small Mexican town on the Yucatán Peninsula.

The impact rock was thought to have been about six miles wide. The problem for animals and plants worldwide wasn't merely the gigantic blast site, which had to have knocked over trees for thousands of miles in every direction. It was the mind-boggling mass of fiery "ejecta" that rose from the site in a plume, then descended all over the Earth at speeds exceeding 17,000 miles an hour, pummeling and burning everything it touched.

"The [heat] radiation would have been comparable to a pizza oven," he says. "Every animal with a body mass of 15 kilograms or more became extinct."

And not just the dinosaurs were cooked. Ocean animals fared poorly in the boiling water near the surface. "Nearly every species" died off following the event, Melosh says.

Burrowing animals, like small mammals, were among the survivors — and some of them evolved into humans.

Melosh is against the idea of using nuclear weapons to deflect Earth-bound asteroids, and he's wary of a deal inked in September between the United States and Russia that expands research along those lines: "I think some of this is being used as an excuse" to conduct nuclear tests in space."

Still, he's not willing to say NASA has exaggerated the threat of impacts. He just thinks deflection can be done by other means, such as ramming an asteroid with an unmanned kamikaze spacecraft.

NASA has given at least $700,000 in grants to a program led by Professor Bong Wie at Iowa State University's Asteroid Deflection Research Center. Wie and his study team, including scientists with the Goddard center, are developing a system that would punch a hole in an asteroid and then follow up by battering a second spacecraft loaded with nuclear weapons into the mass.

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My Voice Nation Help

OH wow, 2018 is not that far wawy at all man.

Ian Calder Drummond
Ian Calder Drummond

I just moved away from Arizona after 14 years And I am being an asshole.

Lisa Kaiser
Lisa Kaiser

Ian, UA has been involved with the NASA Mars missions, its mirror labs creates mirrors of all the major telescopes around the world, its astronomy program is world-renowned.

Toby San
Toby San

The 'redness' of Maricopa county vs. the 'blueness' of Tucson will be apparent.

Brandon Doyle
Brandon Doyle

If that hits us the grid is gonna go down. Then my dad better watch his back. #souppunch

Jason Stafford
Jason Stafford

Good thing its Arizona and not ASU. Though they could launch a bunch of piss drunk frat boys into the meteor and try an explode it that way.

Geary Morris
Geary Morris

They will intentionally direct it to hit ASU Stadium ;-)

Kit Hunn
Kit Hunn

Can't wait for the slew of comments from Phoenicians attempting to bash Tucson without realising that UofA is involved, if not leading, every major NASA mission.

Ian Calder Drummond
Ian Calder Drummond

Great. We are counting on a college in Arizona to save us ? The professors will probably get drunk in the middle of the project.

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