[meteorite-list] A Miss Is As Good As A Mile

From: JoshuaTreeMuseum <joshuatreemuseum_at_meteoritecentral.com>
Date: Fri, 13 Nov 2009 15:36:48 -0500
Message-ID: <C3388F6F44FC442A804DCB8C75638991_at_ET>

Or 9,000 miles as the case may be.

http://cosmiclog.msnbc.msn.com/archive/2009/11/11/2124702.aspx

Space Rock Buzzes Past Earth
Posted: Wednesday, November 11, 2009 1:55 PM by Alan Boyle

Asteroid-watchers say a space rock about as big as a garage came within
9,000 miles (14,000 kilometers) of Earth last Friday, just 15 hours after it
was detected.

Experts quickly determined that the asteroid 2009 VA would miss us - and
even if it came directly at us, it wouldn't have caused a catastrophe.
Nevertheless, the close encounter serves as a reminder that someday a much
bigger rock may well hit us and that it's best to be prepared.

In this week's recap of the event, NASA's Near-Earth Object Program Office
reported that 2009 VA came well within the moon's orbit - so close, in fact,
that the asteroid's orbital path was bent by Earth's gravitational pull.

NASA and other space agencies around the world have been keeping
increasingly close track of near-Earth asteroids and comets, with a strong
assist from amateur astronomers. In this case, the object was first detected
by the Catalina Sky Survey at the University of Arizona. It was quickly
identified by the Minor Planet Center in Cambridge, Mass., as a
close-approaching asteroid. Then NASA experts worked out its orbit and gave
the all-clear.

Why wasn't the rock found sooner? Well, smaller objects are more difficult
to detect in advance, and this one was estimated to be only 7 meters (23
feet) wide. That's nowhere near as big as the 10-kilometer-wide
(6-mile-wide) object that apparently did in the dinosaurs 65 million years
ago - or even the 30-meter-wide (100-foot-wide) Tunguska object that was
thought to have wreaked destruction in a Siberian forest in 1908.

For what it's worth, the Defense Department's Joint Space Operations Center
tracks about 19,000 orbital objects down to the size of 10 centimeters (4
inches), and NASA tracks bits of space junk that are even smaller. But
incoming near-Earth objects are trickier to track until they're almost upon
us.

In the close-but-no-collision category, this one was No. 3 on NASA's list
for cataloged asteroids: A meter-wide (yard-wide) asteroid came within 6,150
kilometers (3,821 miles) in October 2008, while another space rock about the
size of 2009 VA passed within 6,535 kilometers (4,060 miles) in March 2004.

If 2009 VA had entered the atmosphere, it almost certainly would have blown
itself up before hitting the ground - just as a larger asteroid did a month
ago, without warning, in the skies over Indonesia. A somewhat smaller
asteroid met a similar fate in the skies over Africa about 13 months ago.
(Months later, students in Sudan found 4 kilograms (8.7 pounds) of
meteorites that fell to Earth after last year's blast.)

Such atmospheric blow-ups release energy equivalent to about a kiloton of
TNT. In comparison, the Hiroshima atomic bomb set off a roughly 15-kiloton
blast.

So, for several reasons, we shouldn't hit the alarm button over 2009 VA. But
that doesn't mean we should hit the snooze button, either: The Indonesia
blast and the surprise pummeling that Jupiter took back in July are just
foretastes of nasty surprises that could be waiting for us. The more we know
about asteroids and how to fend them off, the better. Here are some reports
that lay out the asteroid threat and what NASA has been doing about it:

  a.. How to track the 'wolves of the solar system'
  b.. NASA downgrades asteroid threat in 2036
  c.. Experts urge more action on asteroids
  d.. Interactive: Close encounters of the asteroid kind
  e.. Newsvine poll: What do you think of the asteroid threat?
Update for 3:35 p.m. ET: I've upped the estimate for the dino-killing
asteroid to a whopping 10 kilometers (6 miles) across. Anything bigger than
1 kilometer wide would be considered capable of causing a global
catastrophe.
Received on Fri 13 Nov 2009 03:36:48 PM PST