[meteorite-list] When I'm 64 ... - Part 2 of 2

From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Mon Mar 28 06:06:39 2005
Message-ID: <DIIE.00000032000035EF_at_paulinet.de>

Hello again, -- Here is part 2:

Alan MacRobert (2005) Asteroid 2004 MN4: A Really
Near Miss (Sky & Telescope, May 2005, pp. 16-17):

When they realized how close the asteroid would pass, astronomers at first thought that
Earth's tidal force might pull it apart into a string of rubble before our very eyes.
(This is what happened to Comet Shoemaker-Levy 9 when it arced close to Jupiter, one
orbit before the resulting string of comet chunks impacted the giant planet in 1994.)
However, calculations by Derek Richardson and Kevin Walsh (University of Maryland) make
this seem very unlikely. Even if 2004 MN4 is a loose "rubble pile" with no internal
strength, it should hold together after all.

But just barely. "My best estimate," says Daniel D. Durda (Southwest Research Institute)
"is that it might have its rotation spun up a bit, and if it's a rubble pile it might have
some internal readjustments. If you were standing on it you might notice rumblings: asteroid-
quakes. This will be an outstanding opportunity for a spacecraft mission to sit on its sur-
face and hear it creak and groan as it goes by. We won't have to ping it to sound its interior
- Mother Nature will do it for us."

And afterward? The close flyby through Earth's gravitational field adds a lot of uncertainty
to the asteroid's future path. However, Chodas and his group say the chance of an impact
later in the 21st century is still insignificant.

It's a good thing, too. The impact energy in 2029 would be about 850 megatons, 15 times
more powerful than the largest hydrogen bomb ever tested and about 60 times more powerful
than the Tunguska explosion over Siberia in 1908. According to Chodas and his colleagues,
"One would expect a similarly close Earth approach by an asteroid of this size only every
1,300 years or so."

Mark your celestial calendar, and if you're on the wrong
side of the world, plan on a vacation to join the party.


Best regards,

Bernd
Received on Mon 28 Mar 2005 06:06:37 AM PST