[meteorite-list] Will Mercury Hit Earth Someday?

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 24 Apr 2008 11:13:38 -0700 (PDT)
Message-ID: <200804241813.LAA02256_at_zagami.jpl.nasa.gov>

http://www.skyandtelescope.com/news/18103199.html

Will Mercury Hit Earth Someday?
by Ken Croswell
Sky & Telescope
April 24, 2008

First, the bad news: the inner solar system is unstable. Given enough
time, Jupiter's gravity could yank Mercury out of its present orbit.

Two new computer simulations of long-term planetary motion - one by
Jacques Laskar (Paris Observatory), the other by Konstantin Batygin and
Gregory Laughlin (University of California, Santa Cruz) - have both
reached the same disturbing conclusion.

Says Laughlin, "The solar system isn't as stable as we'd thought." Both
teams have found that Jupiter's gravity can increase Mercury's orbital
eccentricity over time. Mercury's path around the Sun is already nearly
as elliptical as Pluto's. But Jupiter can make Mercury's orbit so out of
round that it overlaps the path of Venus. A close encounter between them
could send the innermost planet careening off wildly.

"Once Mercury crosses Venus's orbit," Laughlin says, "Mercury is in
serious trouble."

So is Earth.

At that point, the simulations predict Mercury will suffer generally one
of four fates: it crashes into the Sun, gets ejected from the solar
system, it crashes into Venus, or - worst of all - crashes into Earth.

To call this catastrophic is a gross understatement. Such an impact
would kill all life on our planet. Nothing would survive. By contrast,
the asteroid that doomed the dinosaurs 65 million years ago was likely
just 6 miles in diameter; Mercury is 3,032 miles across. The last time
an object about that size hit the Earth, the resulting debris formed our
Moon.

Think we'll escape the chaos by fleeing to Mars? Think again. Even Mars
might not be safe. In one of the computer simulations, the Red Planet
was tossed into the cold of interstellar space.

Now, the good news: there's only about a 1% chance that Mercury will go
crazy before the Sun bloats into a red giant billions of years from now.
"If you're an optimist," says Laughlin, "then you say the glass is 99
percent full."

Laskar, who discovered that Mercury could go wild back in 1994, will
publish his paper <http://arxiv.org/abs/0802.3371> in Icarus; Batygin
(who's still an undergraduate) and Laughlin will publish theirs
<http://www.oklo.org/?p=275> in The Astrophysical Journal.
Received on Thu 24 Apr 2008 02:13:38 PM PDT