[meteorite-list] Whew! Stealth Asteroid Nearly Blindsides Earth (Asteroid 2002 EM7)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:02:30 2004
Message-ID: <200203191657.IAA05120_at_zagami.jpl.nasa.gov>

http://www.cnn.com/2002/TECH/space/03/19/asteroid.blindside/index.html

Whew! Stealth asteroid nearly blindsides Earth
By Richard Stenger
CNN
March 19, 2002

(CNN) -- A sizable asteroid zipped near our planet this month without anyone
noticing because it traveled through an astronomical blind spot, scientists
said.

The space boulder passed Earth within 288,000 miles (461,000 kilometers) --
or 1.2 times the distance to the moon -- on March 8, but since it came from
the direction of the sun, scientists did not observe it until four days
later.

The object, slightly larger than one that flattened a vast expanse of
Siberia in 1908, was one of the 10 closest known asteroids to approach
Earth, astronomers said.

"Asteroid 2002 EM7 took us by surprise. It is yet another reminder of the
general impact hazard we face," said Benny Peiser, a European scientist who
monitors the threat of Earth-asteroid collisions.

If it pierced the atmosphere, the approximately 70-meter-long rock could
have disintegrated and unleashed the energy equivalent of a 4-megaton
nuclear bomb, researchers said.

"If it were over a populated area, like Atlanta, it would have basically
flattened it," said Gareth Williams, associate director of the International
Astronomical Union Minor Planet Center in Boston, Massachusetts.

The rock is considerably smaller than dozens of potential planet killers
1-kilometer in size or larger that lurk in the inner solar system.

Like its larger siblings, asteroid 2002 EM7 follows an elliptical orbit with
an extremely low risk of Earth collision in the coming decades or centuries.

Nonetheless, astronomers maintain that constant surveillance is necessary to
identify more killer rocks in our neighborhood and ensure that none take our
planet by surprise, in particular those traveling near the blinding light of
the sun.

"If one comes from the direction of the sun, we're not going to see it,"
Williams said.

"Often these objects are outside of the Earth's orbit for a significant
amount of time. The key is to detect them when they are outside the Earth's
orbit and predict whether they might hit us in the future from the sun
side."

Even lesser rocks such as 2002 EM7 could do serious damage by plunging into
the ocean and unleashing monster tsunamis on coastal cities, he said.

According to NASA's Jet Propulsion Laboratory, 2002 EM7 could smack into
Earth in 2093.

But don't tell the grandchildren to head to the hills just yet. The odds of
a collision are currently 1 in 10 million and could become even more remote
with more refined calculations.
Received on Tue 19 Mar 2002 11:57:33 AM PST