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

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Caltech

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Robert Tindol, (626) 395-3631

March 14, 2007

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

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.

Related Link

* More about 2003 EL61
http://www.gps.caltech.edu/~mbrown/2003EL61