Asteroid size of 'city block' created crater near Moab; another could strike

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CANYONLANDS — World scientists are meeting in Flagstaff this week to figure out how to defend our planet. The concern is asteroids that might someday collide with Earth.

Many Utahns don't realize it, but our state was evidently right in the bullseye for such a catastrophe a long time ago. The spectacular fireball that exploded over Siberia in February was a reminder — giant rocks can come out of space and threaten us all. Many scientists believe an incomparably bigger catastrophe once hit Utah, and it could happen again anytime, anywhere on the planet.

In this region of soaring cliffs, plunging canyons and windswept mesas, one more giant hole in the ground might not seem especially noteworthy.

But a deep gash in Canyonlands National Park was likely created by something incredible.

"Roughly 100 million years ago, an asteroid about the size of a city block smacked into this part of what is now Utah," said Seth Jarvis, director of Clark Planitarium.

That's the prevailing theory about the 3-mile-wide crater known as Upheaval Dome.

"It would have been the equivalent of detonating some several thousand large hydrogen bombs simultaneously," said Jarvis.

Tourists come now every day. To the eye, the crater is probably less obvious than in used to be.

"Given that it happened so many millions of years ago, you would have expected some erosion and fill in," said Bob Pierce, a tourist from Denver.

But if you can get up very high and look down, it jumps out at you. It's almost a perfect circle, or concentric circles. To put it another way, seen from space, it's an asteroid bullseye just 20 miles from Moab.

"It would have been the equivalent of detonating some several thousand large hydrogen bombs simultaneously." said -Seth Jarvis, Clark Planetarium director

"There's lots and lots of asteroids all over the solar system," said Jarvis. "It's a little bit like a shooting gallery."

The impact theory is not rock solid. Geologist Marjorie Chan said scientists originally thought Upheaval Dome resulted from an uplift of salt deep underground.

"One idea is that the salt has been pushed upwards, almost sort of like a bubble, or like taking a tube of toothpaste and squeezing it and having a bulb come out at the top," said Chan.

In recent years, though, scientists have found more and more evidence of asteroid strikes around the world. It's now the leading theory of Upheaval Dome. Stronger evidence was announced in 2007; when geologists found "shocked quartz" indicating stress from a tremendous impact.

Chan would like to see more evidence — a smoking gun — such as magnetic meteorite fragments found at other impact sites. But she said she thinks there's already a strong case for an asteroid impact at Upheaval Dome.

"Probably a lot of people do feel that it's an impact site, and in my personal opinion, I think that's the best idea so far," Chan said.

When the meteor exploded over Russia in February, it was the biggest in 100 years and the first big one well-documented by video.

"It was pretty cool but scary at the same time," said Brandon George, a Centerville tourist.

By complete coincidence, the Russian fireball hit the same day another big asteroid sailed past Earth just a few thousand miles away.

"That was Mother Nature sort of giving you a dope slap on the backside of the head saying, 'hey, pay attention to these things,'" said Jarvis.

If the Upheaval Dome asteroid hit today, Jarvis said everything in Moab would be set afire — the town bombarded with fiery debris and 400 mile-an-hour winds.

If it smashed into Salt Lake City, it's goodbye Wasatch Front.

"The blast area, the region that would be completely gone and uninhabitable would extend from Ogden to Provo, from Tooele to Heber Valley," Jarvis said.

Jarvis said we need to be getting ready now. That's why scientists are meeting this week in Flagstaff. Many would like a stronger effort to scan the skies.

If they find an asteroid with Earth's name on it, they'll work towards developing technology that can get to it in time and nudge it into a new orbit.


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John Hollenhorst


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