[meteorite-list] Dust Found in Earth Sediment Traced to Breakup ofAsteroid 8.2 Million Years Ago

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu Feb 2 01:52:59 2006
Message-ID: <00ba01c627c5$4bba29d0$aee58c46_at_ATARIENGINE>

Hi, All,

    Not wanting to be too skeptical, jaded, or cynical here,
but when this story first came out, I Googled for papers
on the timing of the Veritas breakup and found there was
a number of papers on the subject of computer modeling
the time scale, all done before this discovery.

    None of them were able to do more than describe
the breakup as "recent," although one swallowed hard
and allowed as how it might be within the last 50,000,000

    Now we have a geological detection of an iridium
spike in sediments at 8,200,000 years and a co-lateral
computer model shows the breakup occured, no, when?
8.2 million years ago, exactly!! That's amazing...

    Exactly how did we refine the results of computer
models from maybe 50,000,000 years to 8.2 million
years in a single bound? Especially since that amounts
to an increase of precision of roughly 1000-fold?

    Gee, just lucky, I guess... Wonder what was wrong
with all those other computer models?

    Also, interesting is that the same team that did these
computer models published in 2002 dating the breakup
of the Karin asteroidal family at 5.8 million years, but
there doesn't seem to be a spike in iridium in sediments
at 5.8 million years. Wonder why not?

    Unless, of course, the 8.2 million year old spike is
not from the Veritas breakup, but the Karin breakup
which was mis-dated by 40% or so, a result to be
expected in long-term regression software.

    It's floating-point error, you know, amazing how it
builds up! The best orbital computer had a mountain
of specially build LSI boards able to handle 80 to 100
digit accuracy in hardware not software, but even it got
wobbly in "only" a few hundred million years and
Venus started wandering around the Solar System!

    Just seems like a huge co-incidence...

Sterling K. Webb

----- Original Message -----
From: "Ron Baalke" <baalke_at_zagami.jpl.nasa.gov>
To: "Meteorite Mailing List" <meteorite-list_at_meteoritecentral.com>
Sent: Wednesday, February 01, 2006 2:54 PM
Subject: [meteorite-list] Dust Found in Earth Sediment Traced to Breakup
ofAsteroid 8.2 Million Years Ago

> http://pr.caltech.edu/media/Press_Releases/PR12787.html
> Dust Found in Earth Sediment Traced to Breakup of the Asteroid
> Veritas 8.2 Million Years Ago
> Caltech News Release
> Contact: Robert Tindol (626) 395-3631 tindol_at_caltech.edu
> January 18, 2006
> PASADENA, Calif.--In a new study that provides a novel way of looking at
> our solar system's past, a group of planetary scientists and geochemists
> announce that they have found evidence on Earth of an asteroid breakup
> or collision that occurred 8.2 million years ago.
> Reporting in the January 19 issue of the journal Nature, scientists from
> the California Institute of Technology, the Southwest Research Institute
> (SwRI), and Charles University in the Czech Republic show that core
> samples from oceanic sediment are consistent with computer simulations
> of the breakup of a 100-mile-wide body in the asteroid belt between Mars
> and Jupiter. The larger fragments of this asteroid are still orbiting
> the asteroid belt, and their hypothetical source has been known for
> years as the asteroid "Veritas."
> Ken Farley of Caltech discovered a spike in a rare isotope known as
> helium 3 that began 8.2 million years ago and gradually decreased over
> the next 1.5 million years. This information suggests that Earth must
> have been dusted with an extraterrestrial source.
> "The helium 3 spike found in these sediments is the smoking gun that
> something quite dramatic happened to the interplanetary dust population
> 8.2 million years ago," says Farley, the Keck Foundation Professor of
> Geochemistry at Caltech and chair of the Division of Geological and
> Planetary Sciences. "It's one of the biggest dust events of the last 80
> million years."
> Interplanetary dust is composed of bits of rock from a few to several
> hundred microns in diameter produced by asteroid collisions or ejected
> from comets. Interplanetary dust migrates toward the sun, and en route
> some of this dust is captured by the Earth's gravitational field and
> deposited on its surface.
> Presently, more than 20,000 tons of this material accumulates on Earth
> each year, but the accretion rate should fluctuate with the level of
> asteroid collisions and changes in the number of active comets. By
> looking at ancient sediments that include both interplanetary dust and
> ordinary terrestrial sediment, the researchers for the first time have
> been able to detect major dust-producing solar system events of the past.
> Because interplanetary dust particles are so small and rare in
> sediment-significantly less than a part per million-they are difficult
> to detect using direct measurements. However, these particles are
> extremely rich in helium 3, in comparison with terrestrial materials.
> Over the last decade, Ken Farley has measured helium 3 concentrations in
> sediments formed over the last 80 million years to create a record of
> the interplanetary dust flux.
> To assure that the peak was not a fluke present at only one site on the
> seafloor, Farley studied two different localities: one in the Indian
> Ocean and one in the Atlantic. The event is recorded clearly at both
> sites.
> To find the source of these particles, William F. Bottke and David
> Nesvorny of the SwRI Space Studies Department in Boulder, Colorado,
> along with David Vokrouhlicky of Charles University, studied clusters of
> asteroid orbits that are likely the consequence of ancient asteroidal
> collisions.
> "While asteroids are constantly crashing into one another in the main
> asteroid belt," says Bottke, "only once in a great while does an
> extremely large one shatter."
> The scientists identified one cluster of asteroid fragments whose size,
> age, and remarkably similar orbits made it a likely candidate for the
> Earth-dusting event. Tracking the orbits of the cluster backwards in
> time using computer models, they found that, 8.2 million years ago, all
> of its fragments shared the same orbital orientation in space. This
> event defines when the 100-mile-wide asteroid called Veritas was blown
> apart by impact and coincides with the spike in the interplanetary
> seafloor sediments Farley had found.
> "The Veritas disruption was extraordinary," says Nesvorny. "It was the
> largest asteroid collision to take place in the last 100 million years."
> As a final check, the SwRI-Czech team used computer simulations to
> follow the evolution of dust particles produced by the 100-mile-wide
> Veritas breakup event. Their work shows that the Veritas event could
> produce the spike in extraterrestrial dust raining on the Earth 8.2
> million years ago as well as a gradual decline in the dust flux.
> "The match between our model results and the helium 3 deposits is very
> compelling," Vokrouhlicky says. "It makes us wonder whether other helium
> 3 peaks in oceanic cores can also be traced back to asteroid breakups."
> This research was funded by NASA's Planetary Geology & Geophysics
> program and received additional financial support from Czech Republic
> grant agency and the National Science Foundation's COBASE program. The
> Nature paper is titled "A late Miocene dust shower from the breakup of
> an asteroid in the main belt."
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Received on Thu 02 Feb 2006 01:52:54 AM PST

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