[meteorite-list] Scientists Learn About Origins of Earth by Studying Dayton Meteorite

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Jul 17 01:07:44 2006
Message-ID: <200607170505.WAA25136_at_zagami.jpl.nasa.gov>

http://www.daytondailynews.com/localnews/content/localnews/daily/071706meteor.html

Scientists learn about origins of Earth by studying meteorite

Dayton find provides key clues and offers some interesting
differences from others.

By Steve Bennish
Dayton Daily News
July 16, 2006

DAYTON - Nobody is certain of its exact history, but a meteorite that
lore says landed in the 1890s at the Montgomery County Fairgrounds has
provided important clues as to how the solar system formed.

Of all the otherworldly buzz linked to Dayton since manned flight took
off and Hollywood extraterrestrials slithered onto the scene, few
celestial objects are as little-known to the public as a chunk of iron
space debris known as the Dayton meteorite now housed in a secure
cabinet at the Smithsonian Institution in Washington, D.C.

This particular meteorite, celebrated in scientific circles, is one of
35,000 specimens stored in the National Museum of Natural History
Building on the National Mall.

It's not in its original shape because so many slices have been taken
for scientific research. The meteorite's unusual composition has made it
a popular subject, said Tim McCoy, the Smithsonian's meteorite curator.
McCoy is quick to note that his Ph.D. research dealt with the Dayton
meteorite.

Up to 3 million visitors annually who pass through the spectacular,
glittering displays of gems and minerals, including the Hope Diamond,
can see a piece of the meteorite.

The Dayton Daily News published articles about the meteorite in 1951,
and in 1966. But in the years that followed, the meteorite was largely
forgotten, even as it was being sliced and diced and examined by
inquiring minds.

Meteorite's history

As fall faded into winter in 1951, Chinese forces invaded the capital of
Tibet, NATO accepted Greece and Turkey as members and on Oct. 4, the
Daily News reported that Smithsonian Institution officials identified
the Dayton meteorite as Ohio's ninth. Oddly enough, it was noted, six of
those nine verified Ohio meteorites had fallen in or near the Miami
Valley. The Dayton meteorite, however, already had a colorful history.

It had been sent to the Smithsonian by Stuart H. Perry, editor and
publisher of the Adrian (Mich.) Telegram, who also was an amateur
meteorite collector.

Perry came into possession of the iron through L.R. Keyser, a University
of Cincinnati student whose grandfather, Albert Seifert, ran a
concession stand at county fairs.

The story handed down from the family is that during a summer evening in
1892 or 1893, the meteor came screaming from the sky before it hit the
Montgomery County Fairgrounds with such force that it buried itself four
feet into the ground. It was smoldering when recovered.

Scientists believe otherwise. No mention of the meteor's fall ever made
it into scientific literature, and Dayton at the time was flourishing.
Further, the meteorite showed signs of weathering that indicated it
hadn't landed in modern times.

It's quite possible Seifert bought the meteorite from a farmer he met at
a fair, scientists now believe. Seifert perhaps had a motive to hype the
meteorite's recovery. As a concession stand operator, he had the
meteorite on hand during lengthy travels on the county fair circuit
through Ohio, Illinois and Indiana, and he likely used it as a novel
customer draw, McCoy said.

"People could see (it) ... and buy something from the concession
stand,'' McCoy said.

How meteors form

Falling stars continue to fascinate. Andrea Koziol, professor of
mineralogy at the University of Dayton and president of the Dayton Gem
and Mineral Society, said she receives three or four inquiries a year
from those who believe they've found a meteorite. She has yet to
identify the real thing. The key sign is what is known as a fusion
crust, indicating a fiery descent through the atmosphere, Koziol said.

"As the meteor comes in, it gets very hot. But only the surface gets
hot. The exterior is burned and melted. That is the key giveaway," she said.

Meteorite revealed

Whether dug up by plow in a farmer's field or discovered smoldering
beside a fairground horse barn, no one will probably never know.

What is known, McCoy said, is that the 4.5 billion-year-old meteor once
orbited the sun in the Asteroid Belt between Mars and Jupiter until it
collided with another object, which sent it hurtling in our direction.

Iron meteorites are generally thought to have formed in the cores of
asteroids, McCoy said. The Dayton meterorite solidified later than other
meteorites, which left it with a very high percentage of nickel.

It led to other oddities, such as having two phosphate minerals present
that occur nowhere else in the solar system.

Meteorite's meaning

What all this means is that although technology isn't advanced enough to
allow us to sample the Earth's core, we can learn how it might be
composed by studying meteorites.

"When the hot, molten core crystallizes and changes from a liquid to a
solid, certain elements give us clues to how that happens," McCoy said.

It's significant, McCoy said, that while most iron meteorites contain 5
percent to 10 percent nickel, Dayton contains 17.6 percent. Nickel is an
element that provides clues about the transition from a molten to a
solid state.

The later an iron meteorite crystallizes, the more nickel it will
contain, McCoy said. "To make matters more interesting, Dayton probably
formed in a different way from our own core. As asteroids began to heat
up and melt, the metal that melted first may have formed a very small
core. Only with much more heating and melting did a large core, like the
Earth's, form," McCoy said.

"The asteroid from which Dayton formed apparently never reached this
higher stage of melting, so it came from a very small core. One of the
interesting features of this core is that it contained bits of all kinds
of other stuff, including elements like phosphorus, sulfur and carbon
and even pieces of silicates like those that you might find in rocks
around you. This core had a long time to stew and the elements and rock
bits began to react."

The reaction produced minerals found nowhere else, McCoy said. Brianite
and panethite are phosphates - much like fertilizers or the minerals in
teeth - but they have very strange compositions, he added.

"Dayton is the weirdest one of its group," McCoy said. "Again, that
makes it special and the reason scientists want to study it."

Ultimately, the meteorite offers clues to how the Earth's core might
have formed and the chemical reactions that occurred during the birth of
our planet, McCoy said.

"Whether it is from the city of Dayton or not, the citizens there should
be justifiably proud to have contributed a one-of-a-kind meteorite that
answers - and continues to pose - such profound questions," he said.
Received on Mon 17 Jul 2006 01:05:14 AM PDT