[meteorite-list] Astronomers Survey Sky For Big Asteroids

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:55:46 2004
Message-ID: <200201141647.IAA06676_at_zagami.jpl.nasa.gov>

http://www.floridatoday.com/!NEWSROOM/localstoryA8730A.htm

Astronomers survey sky for big asteroids

Researchers try to increase alert time for such objects

By Steven Siceloff
FLORIDA TODAY
January 13, 2002

CAPE CANAVERAL -- The odds of dying from an asteroid impact are better than
winning the lottery, researchers said, but the nation puts little effort
into preparing for the possibility.

The search for asteroids is critical if humans are to get a chance to rescue
themselves, officials said. That's why Congress ordered NASA to identify
almost all the objects two-thirds of a mile or larger by 2008. So far, more
than 300 have been identified as possible threats to Earth.

"We're running as fast as we can with the technology we have," said
astronomer Stephen Pravdo, project manager for the Near Earth Asteroid
Tracking project.

But by allocating only a few million dollars a year to an effort that must
identify 90 percent of the objects over six years, Congress is playing the
odds, betting scientists will win.

They face a daunting task. The hazard was highlighted Jan. 7, when a
300-yard-long rock missed Earth by 520,000 miles. The asteroid, named YB5,
would have destroyed an area the size of France had it hit this planet.

Researchers had almost no warning, and spotted it only two weeks before its
closest approach.

Increasing the alert time for such objects is the sole goal for the fewer
than 100 astronomers who have turned their attention to so-called near-Earth
objects. They hope to give earthlings enough time to divert an asteroid in
case one is found headed this way, even though the chances are slim there
will be a major impact during their lifetimes.

"I don't think there is a right answer for how seriously to take it," said
Clark Chapman, an asteroid impact specialist at the Southwest Research
Institute in Boulder, Colo. "A big asteroid hasn't hit in recorded human
history, but it could happen next year. The chances are the same as dying in
an airplane crash, with or without terrorists."

Congress authorized as much as $7 million a year for a survey of the solar
system near Earth that hopes to find 90 percent of all the objects larger
than two-thirds of a mile, but only half of that is ever allocated, David
Morrison said. He heads NASA's asteroid and comet impact research effort at
Ames Research Center in California.

The money has provided technological leaps for asteroid astronomers.

Working each year with slightly more than 1/10th the cost of the Odyssey
robotic mission to Mars, astronomers have developed computers that turn
telescopes into celestial sentries.

"Up to the early 1990s, it was a couple (asteroids found) per year," Pravdo
said. "Now it's hundreds per year, sometimes 30 a month."

So far this month, the team has found four new objects, one of which passes
close enough to Earth to be considered dangerous, though it is not expected
to hit the planet. Researchers have spotted 1,739 near-Earth objects, the
majority since 1997. More than 500 of them are larger than two-thirds of a
mile, with 367 classified as potential threats.

Don Yeomans, manager of NASA's Near Earth Objects program, estimated there
are about 1,000 asteroids in the solar system larger than two-thirds of a
mile. There could be 100,000 rocks big enough to chew up a state if they hit
Earth.

When Pravdo and astronomers around the world find a new object, other
astronomers use special devices and radar telescopes to determine what it is
made of and calculate the exact path it will take.

The objects of most concern are the relatively large rocks that could
explode over a city and asteroids almost a mile wide that could spell a new
extinction. Earth's atmosphere absorbs the impact of countless small objects
daily.

There are few signs of past meetings with asteroids. One of the most famous
is a mile-wide crater in Arizona. A 100-foot meteor traveling 40,000 mph is
thought to have excavated the desert 50,000 years ago.

Mexico's Yucatan Peninsula is thought to be part of the crater left by a
massive boulder from space that eliminated the dinosaurs 65 million years
ago.

"We're dealing with this hazard that is very unlikely to happen, but if it
does happen, it will be the biggest event to happen to humanity since we
emerged from the caves," Chapman said.

Morrison puts the odds of dying from an asteroid impact at 1 in 20,000
during a typical lifetime -- the same as dying in a plane crash.

The only way to know with relative certainty is to look for the objects and
figure out where they are going.

"The issue is not statistics, but when the next hit will take place,"
Morrison said. "That is why Spaceguard is finding and tracking real objects,
not trying to improve the statistics."

Many in the space community argue for more funding to quicken the pace of
discovery, and then work on finding smaller but lethal objects.

"If we could get the budget up to $10 million a year, we could accomplish
what we need to accomplish," said Marc Schlather, director of the
Washington, D.C.-based ProSpace grass-roots organization.

Morrison said the Earth needs 10 to 20 years warning to deal with an
incoming object. That is possible with a thorough survey of the heavens. The
country needs the time to develop rockets, spacecraft and plans to divert
the asteroid.

Bob Farquhar, who led the NEAR mission that landed on the asteroid Eros last
year, said the space program should develop a small shuttle craft that can
travel from space station Alpha to deep space on short order. With that
capacity, a crew could intercept a killer asteroid years before it has a
chance to threaten the planet.

Shuttle astronauts could attach a small rocket motor that gradually would
push the object's orbit away from Earth. The Hollywood solution -- nuclear
warheads shot at or detonated inside an asteroid -- would not likely solve
the problem, most agree

"That might break it up into smaller pieces, and I'm not sure if that's good
or bad," Farqua said.

For now, Farqua said it is important the country understand there is a
danger that can be averted, but the risk is small during this lifetime.

"The rate they're going, the politicians are still not taking this threat
very seriously," he said. "I don't know what it's going to take, maybe a
small one hitting us first."
Received on Mon 14 Jan 2002 11:47:40 AM PST