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Dec.
21, 2007: Astronomers funded by NASA are monitoring
the trajectory of an asteroid named 2007
WD5 that is expected to cross the orbital path of Mars
early next year. Calculations by NASA's Near-Earth Object
Office at the Jet Propulsion Laboratory indicate that the
164-ft wide asteroid may pass within 30,000 miles of Mars
at about 6 a.m. EST on Jan. 30, 2008.
"Right
now asteroid 2007 WD5 is about half-way between the Earth
and Mars and closing the distance [to Mars] at a speed of
about 27,900 miles per hour," said Don Yeomans, manager
of the Near Earth Object Office at JPL.
Above:
This artist rendering uses an arrow to show the predicted
path of the asteroid on Jan. 30, 2008. The orange swath indicates
the area it is expected to pass through. Mars may or may not
be in the asteroid's path. Image credit: NASA/JPL. [animation]
There is a 1-in-75 chance of 2007 WD5 hitting Mars; researchers
can't be more confident than that because of uncertainties
in the asteroid's orbit. If this unlikely event were to occur,
however, the strike would happen somewhere within a broad
swath across the planet north of where the Opportunity rover
is.
"We
estimate such impacts occur on Mars every thousand years or
so," said Steve Chesley, a scientist at JPL. "If
2007 WD5 were to thump Mars on Jan. 30, we calculate it would
hit at about 30,000 miles per hour and might create a crater
more than half-a-mile wide." The Mars Rover Opportunity
is currently exploring a crater approximately this size.
Such a collision could release about three megatons of energy.
Scientists believe an event of comparable magnitude occurred
here on Earth in 1908 in Tunguska, Siberia, but no crater was
created. The object was disintegrated by Earth's atmosphere
before it hit the ground, although the air blast devastated
a large area of unpopulated forest. The Martian atmosphere is
much thinner than Earth's so a similar sized impactor would
be more likely to reach the ground.
Asteroid
2007 WD5 was first discovered on Nov. 20, 2007, by the NASA-funded
Catalina Sky Survey and put on a "watch list" because
its orbit passes near the Earth. Further observations from
both the NASA-funded Spacewatch at Kitt Peak, Ariz., and the
Magdalena Ridge Observatory in New Mexico gave scientists
enough data to determine that the asteroid was not a danger
to Earth, but could potentially impact Mars.
Because
the asteroid has been tracked for little more than a month,
there is still some uncertainly about the path it will take.
"Over the next five weeks, we hope to gather more information
from observatories so we can further refine the asteroid's
trajectory," says Yeomans. More data could eliminate
or confirm the possibility of an impact.
Stay
tuned for updates from Science@NASA.
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Production Editor:
Dr. Tony Phillips | Credit: Science@NASA
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