Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown@nasa.gov
WASHINGTON -- Researchers anticipate
that asteroid 2011 AG5, discovered in January 2011, will fly safely past and
not impact Earth in 2040.
Current findings and analysis data were
reported at a May 29 workshop at NASA's Goddard Space Flight Center in
Greenbelt, Md., attended by scientists and engineers from around the world.
Discussions focused on observations of potentially hazardous asteroids (PHAs).
Observations to date indicate there is a
slight chance that AG5 could impact Earth in 2040. Attendees expressed
confidence that in the next four years, analysis of space and ground-based
observations will show the likelihood of 2011 AG5 missing Earth to be greater
than 99 percent.
Measuring approximately 460 feet (140
meters) in size, the space rock was discovered by the NASA-supported Catalina
Sky Survey operated by the University of Arizona in Tucson. Several
observatories monitored 2011 AG5 for nine months before it moved too far away
and grew too faint to see.
"While there is general consensus
there is only a very small chance that we could be dealing with a real impact
scenario for this object, we will still be watchful and ready to take further
action if additional observations indicate it is warranted," said Lindley
Johnson, program executive for the Near-Earth Object (NEO) Observation Program
at NASA Headquarters in Washington.
Several years ago another asteroid,
named Apophis, was thought to pose a similar impact threat in 2036. Additional
observations taken from 2005 through 2008 enabled NASA scientists to refine
their understanding of the asteroid's path, which showed a significantly
reduced likelihood of a hazardous encounter.
"Any time we're able to observe an
asteroid and obtain new location data, we're able to refine our calculations of
the asteroid's future path," said Don Yeomans, manager of NASA's NEO
Program Office at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "When
few observations exist, our initial orbit calculation will include a wider
swath to account for uncertainties. With more data points, the knowledge of the
potential positions of the asteroid improves and the swath becomes smaller --
typically eliminating the risk of an impact."
Observations of 2011 AG5 have been
limited to date because of its present location beyond the orbit of Mars and in
the daytime sky on the other side of the sun. In fall 2013, conditions will
improve to allow space- and ground-based telescopes to better track the
asteroid's path. At that time, 2011 AG5 will be 91 million miles (147 million
kilometers) from Earth but favorably located for observations in the late
evening sky.
The level of hazard will gain even more
clarity in 2023, when the asteroid is approximately 1.1 million miles (1.8
million kilometers) from Earth. If 2011 AG5 passes through a 227-mile-wide
(365-kilometer) region in space called a keyhole in early February 2023,
Earth's gravitational pull could influence the object's orbital path just
enough to bring it back for an impact on February 5, 2040. If the asteroid
misses the keyhole, an impact in 2040 will not occur.
"Given our current understanding of
this asteroid's orbit, there is only a very remote chance of this keyhole
passage even occurring," said Johnson.
Although scientists widely expect it to
be a safe flyby, they acknowledge the slight chance that computed odds could
rise as a result of observations to be taken from 2013 to 2016. According to
the experts at the workshop, even if the odds do increase, there is still ample
time to plan and carry out at least one of several viable missions to change
the asteroid's course.
PHAs are a subset of the larger group of
near-Earth asteroids. They have the closest orbits to Earth's, coming within 5
million miles (about 8 million kilometers). They are large enough to enter
Earth's atmosphere intact and cause damage on at least a local scale. Damage
from an asteroid the size of 2011 AG5 could cover a region at least a hundred
miles wide.
NASA established the NEO Program in 1998
to coordinate the agency's efforts to detect, track and characterize
Earth-approaching NEOs and comets larger than 1 kilometer in size. The program
now also searches for NEOs as small as object 2011 AG5. NASA supports NEO
observation, tracking and analysis activities worldwide. Activities are
coordinated through the NEO Program Office at JPL.
To read the workshop report and
findings, visit http://neo.jpl.nasa.gov/.
For information about NASA asteroid
missions and activities, visit http://www.nasa.gov/asteroids.
EDITOR'S NOTE: Lindley Johnson and Don
Yeomans are available for media interviews. To coordinate a time and date,
email Dwayne Brown at dwayne.c.brown@nasa.gov.
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