[meteorite-list] Kuiper-belt Object 2003 EL61 Was Broken up by Massive Impact 4.5 Billion Years Ago

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 14 Mar 2007 10:03:42 -0700 (PDT)
Message-ID: <200703141703.l2EH3g203768_at_zagami.jpl.nasa.gov>

Caltech News Release
Embargoed until 10:00 AM PDT, Wednesday, March 14, 2007

Kuiper-belt Object Was Broken up by Massive Impact 4.5 Billion Years
Ago, Study Shows

For more information go to www.gps.caltech.edu/~mbrown/2003EL61

PASADENA, Calif.--In the outer reaches of the solar system, there is
an object known as 2003 EL61 that looks like and spins like a
football being drop-kicked over the proverbial goalpost of life.

Still awaiting a more poetic name, 2003 EL61 largely escaped the
media hubbub during last year's demotion of Pluto, but new findings
could make it one of the most important of the Kuiper-belt objects
for understanding the workings of the solar system. In this week's
Nature, the original discoverer of the body, Mike Brown, announces
with his colleagues that an entire family of bodies seems to have
originated from a catastrophic collision involving 2003 EL61 about
the time Earth was forming.

Brown and his team base their assumptions on similar surface
properties and orbital dynamics of smaller chunks still in the
general vicinity. They conclude that 2003 EL61 was spherical and
nearly the size of Pluto until it was rammed by a slightly smaller
body about 4.5 billion years ago, leaving behind the football-shaped
body we see today and a couple of moons, as well as many more
fragments that flew away entirely.

"Some of these chunks are still in orbit around the sun and very near
the orbit of 2003 EL61 itself," says Brown, a professor of planetary
astronomy at the California Institute of Technology. "The impact made
a tremendous fireball, and large icy chunks of the big object split
off and went flying into space, leaving behind a huge ice-covered
rock spinning end over end every four hours.

"It spins so fast that it has pulled itself into the shape of an
American football, but one that's a bit deflated and stepped on,"
Brown adds.

A significant part of the finding is that the collision occurred in a
region of space where orbits are not very stable. "In most places,
things go around the sun minding their own business for 4.5 billion
years and nothing happens," says Brown. "But in a few places, though,
orbits go crazy and change and eventually objects can find themselves
on a trajectory into the inner solar system, where they would be what
we would then call comets."

As a consequence, many of the shards probably made their way to the
inner solar system, and a few have undoubtedly hit Earth in the past.
The study thus provides new ideas about how the solar system evolves,
and how comets fit into the big picture.

Brown adds that 2003 EL61 will put on quite a show in about a billion
years, if anyone is still around to enjoy it.

"It's a long time to wait, but 2003 EL61 could become by far the
largest comet in eons," Brown says. "It will be something like 6,000
times brighter than Hale-Bopp a few years ago."

The other authors of the paper are Kristin Barkume, Darin Ragozzine,
and Emily Schaller, all graduate students in planetary science at
Caltech.

Contact:
Robert Tindol
tindol at caltech.edu
(626) 395-3631
Received on Wed 14 Mar 2007 01:03:42 PM PDT