http://www.washingtonpost.com/national/health-science/as-asteroid-flies-by-scientists-will-stare/2011/11/02/gIQA8FTngM_story.html
As asteroid flies by, scientists will stare
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By Brian Vastag, Thursday, November 3, 2:35 PM
An asteroid the size of an aircraft carrier will zoom past Earth on Tuesday
just inside the orbit of the moon.
The space rock poses no danger, as its nearest approach will be a
comfortable 202,000 miles distant. But the event marks the closest flyby of
an asteroid this large since 1976, according to NASA.
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Asteroid 2005 YU55 has a name only a scientist could love. They're also
loving the chance to stare at the nearly round, slowly spinning chunk of
space debris as it flies by at some 30,000 mph.
"It will be scanned and probed and scanned some more," said Marina Brozovic,
an asteroid researcher at NASA's Jet Propulsion Laboratory.
Starting Friday, Brozovic will ping the approaching asteroid with radar from
giant dishes at Goldstone, Calif. She wants to map every crater and boulder
while refining estimates of the asteroid's path, which swings inside the
orbit of Venus and then out near Mars, crossing Earth's orbit.
Meanwhile, telescopes in Arizona and Hawaii will analyze light reflected
from the asteroid to determine more precisely what it's made of. Already
scientists know it's darker than charcoal, because it's a "C-type" asteroid,
heavy with carbon and silicate minerals. Astronomers will also look for
signs of water.
Similar asteroids that have plunged to Earth - called carbonaceous
chondrites - hold within them amino acids and other building blocks of life.
"These are the objects that probably seeded the early Earth with
carbon-based materials and water that allowed life to form," said Don
Yeomans, manager of NASA's Near Earth Object Program, which tracks space
objects that veer close to our planet.
Since a humble start at a single telescope in the 1980s, NASA's $5
million-per-year asteroid-tracking program has matured to the point where
the agency said in September that it has detected more than 90 percent of
"planet killer" asteroids, those bigger than one kilometer in diameter. None
will hit Earth in the foreseeable future, the agency has said.
The tracking program detects hundreds of smaller space rocks each year,
closely watching their orbits. So far, none of those pose a threat either.
In the past, giant asteroids have crashed into Earth and devastated life.
The most famous, at least seven miles wide, blasted a crater in the Yucatan
Peninsulasome 65 million years ago, triggering a cataclysm that probably
wiped out the dinosaurs.
If a space rock the size of 2005 YU55 ever hit Earth, it would explode like
500 nuclear bombs, trigger a 7.0 magnitude earthquake and, if it splashed
down in the ocean, generate a 70-foot tsunami, said Purdue University's Jay
Melosh.
Already, scientists have determined this asteroid poses no threat for the
next century or so.
Still, they're treating the flyby as a drill, a chance to refine their
tracking skills. Said asteroid hunter Richard Binzel of MIT: "If one were
ever found on an incoming trajectory, we'll want to apply all the techniques
we are learning now."
Phil Whitmer
Joshua Tree Earth & Space Museum
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