Russian Fireball Won't Be Last Surprise Asteroid Attack
by Mike Wall, SPACE.com Senior Writer
Date: 16 February 2013 Time: 08:00 AM ET
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What appears to be a meteor trail over eastern Russia is
seen in this image released Feb. 15, 2013, by the Russian Emergency
Ministry. The meteor fall included a massive blast, according to Russian
reports.
CREDIT: Russian Emergency Ministry
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The world will have to live with surprise asteroid attacks on the scale of Friday's Russian fireball, at least for a while.
The meteor that
exploded over the Russian city of Chelyabinsk
without warning Friday (Feb. 15), damaging hundreds of buildings and
wounding more than 1,000 people, was caused by a space rock about 50
feet (15 meters) wide, researchers said.
Asteroids
of this size are both difficult to detect and incredibly numerous, so
it will take a long time for astronomers to find and map out the orbits
of all the potentially dangerous ones. Besides, researchers have bigger
fish to fry.
"Defending the Earth against tiny asteroids such as the one that passed
over Siberia and impacted there is a challenging issue that is
something that is not currently our goal," Paul Chodas, a scientist with
the Near Earth Object Program Office at NASA's Jet Propulsion
Laboratory in Pasadena, Calif., told reporters Friday (Feb. 15). [
Meteor Blast Over Russia Feb. 15: Complete Coverage]
"We are focusing on the larger asteroids first," Chodas added. "They are the ones that are the most hazardous."
Millions of asteroids
In 1998, Congress directed NASA to find all of the
near-Earth asteroids
at least 0.6 miles (1 kilometer) wide that could pose an impact risk to
Earth. Such large space rocks have the potential to end human
civilization if they hit us.
NASA met that challenge several years ago, and its scientists have now
identified 95 percent of the 980 such mountain-size asteroids thought to
be cruising through Earth's neighborhood. Happily, none of the known
behemoths pose any threat to our planet for the foreseeable future.
But the outlook isn't so rosy for smaller asteroids.
Observations by NASA's WISE space telescope, for example, suggest that
about 4,700 asteroids at least 330 feet (100 m) wide come uncomfortably
close to our planet at some point in their orbits. To date, astronomers
have detected less than 30 percent of these objects, which could destroy
an area the size of a state if they slammed into Earth.
And researchers have spotted less than 1 percent of asteroids at least
130 feet (40 m) wide, according to officials with the B612 Foundation, a
nonprofit organization dedicated to predicting and preventing
catastrophic asteroid strikes.
Space rocks of this size can cause severe damage on a local scale, as
the 1908 "Tunguska Event" shows. That year, a 130-foot-wide object
exploded over Siberia's Podkamennaya Tunguska River, flattening roughly
825 square miles (2,137 square km) of forest.
A space rock in this size
class
gave Earth a close shave Friday. The 150-foot-wide (45 m)
asteroid 2012 DA14
— which was just discovered in February 2012 — cruised within 17,200
miles (27,000 km) of our planet, marking the closest approach of such a
big space rock that was ever predicted in advance.
Overall, scientists think 1 million or more near-Earth asteroids are
lurking out there, and just 9,600 have been identified to date.
Improving the search
Searching near-Earth space in infrared wavelengths is a good way to
find potentially hazardous asteroids, Chodas said, and many other
scientists agree.
The B612 Foundation, in fact, plans to launch an infrared
space telescope called Sentinel
to a Venus-like orbit in 2018. From there, the instrument would peer
out toward Earth's neighborhood without having to contend with the sun's
overwhelming glare.
In less than six years of operation, Sentinel should spot 500,000
near-Earth asteroids, including the few remaining undetected
mountain-size space rocks and more than 50 percent of the 130-footers,
B612 officials have said. The goal is to find big, dangerous objects
several decades before they may hit us, giving humanity enough lead time
to mount a deflection mission.
But even if Sentinel lives up to its billing, many thousands of
130-foot asteroids would remain undetected, as would even more objects
the size of the Russian fireball's parent body. So we're likely to be
caught off guard again, as the people of Chelyabinsk were Friday.
"NASA has recognized that asteroids and meteoroids and orbital debris
pose a bigger problem than anybody anticipated decades ago," said Bill
Cooke, head of NASA's Meteoroid Environment Office at Marshall Space
Flight Center in Huntsville, Ala.
RT
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