[meteorite-list] New Hall for Meteorites Old Beyond Imagining

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:29:58 2004
Message-ID: <200309190428.VAA03069_at_zagami.jpl.nasa.gov>

http://www.nytimes.com/2003/09/19/arts/design/19METE.html

New Hall for Meteorites Old Beyond Imagining
By JOHN NOBLE WILFORD
New York Times
September 19, 2003

Spacecraft travel hundreds of millions of miles across the solar system to
see what's out there and report back. Yet every day about 100 tons of space
stuff comes calling on us, unannounced and mostly undetected, a global fall
of extraterrestrial dust grains. Occasionally, a dark pebble or fist-size
object will rain down; only rarely, fortunately, something the menacing size
of a boulder or larger.

No one contends that these messengers from the outer solar system render
spacecraft exploration superfluous. But the scientific value of meteorites
has indeed soared in recent years. Encapsulated in the rocks, scientists are
finding, are striking clues to the origin and early evolution of the Sun's
family of planets.

The considerable advances in meteorite discovery and interpretation prompted
the American Museum of Natural History to shut down its exhibition of
meteorites six months ago for a complete makeover. Now the renovated Arthur
Ross Hall of Meteorites is ready for visitors, opening tomorrow.

"The old hall was a mishmash in concept," said Dr. Denton Ebel, the curator
in charge of the renovation. "The hall was more of a display of our
meteorite collection, organized by classification of specimen types. The new
hall is more about what meteorites tell us about the history of the solar
system."

Although the hall's floor space is the same as before, the ceiling has been
raised, lighting has been improved and the new displays have been arranged
in a graceful circular pattern. David Harvey, the museum's director of
exhibitions, said these changes should give the hall a more spacious feel
than it had before. The central display, though, will be familiar to
previous visitors, for reasons of showmanship and inevitability.

In choosing a focal point for an exhibition, museum curators usually have a
range of options. Not so when dealing with a 34-ton gorilla of a rock. It is
Ahnighito, the largest meteorite on display at any museum, brought from
Greenland by the Arctic explorer Robert E. Peary more than a century ago.

Wherever you put such a gigantic iron meteorite, it will attract all eyes,
so it might just as well be given center stage, where it stood before. There
was also a practical reason. To support such a weight, the floor at that
place had already been reinforced with support posts extending into the
museum basement and all the way to Manhattan bedrock.

(The museum also had little choice in its other recent renovation. Who could
imagine hanging the great blue whale replica from anywhere but the center
ceiling of the Hall of Ocean Life?)

Entering the meteorite hall, one is drawn to the platform where Ahnighito
(pronounced ah-nah-HEET-o) rests. There, one's introduction to the lore and
facts and importance of meteorites begins. They are pieces of planets,
asteroids, comets and other materials from space. Most of them come from the
asteroid belt between Mars and Jupiter.

Ahnighito (the name means the Tent in Inuit) is itself a hefty fragment of a
200-ton meteorite that broke apart as it fell ages ago on Cape York,
Greenland. Two smaller pieces, known as the Woman and the Dog, share the
platform. More than 130 other meteorites are on display, including five
pieces that have been traced by their chemistry back to Mars. Three lunar
samples brought back by Apollo astronauts are also on view.

It happened that in 1969, the year astronauts first went collecting Moon
rocks, a huge meteorite exploded into a thousand pieces over northern
Mexico. The fall of the Allende meteorite - named for a village near where
the fragments landed - set in motion the current revolution in meteoritic
research. Scientists who had geared up to study Moon rocks used their
advanced instruments for an examination of Allende more comprehensive than
any meteorite had ever been subjected to.

Allende is more than 4.5 billion years old - virtually the age of the solar
system - and tiny diamonds embedded in pieces of the meteorite, are even
older. Formed in explosions of dying stars, the diamond grains were
scattered through space, some of them winding up in Allende. The story of
Allende and the diamonds is an engrossing part of the exhibition.

As Dr. Ebel pointed out on a tour of the hall, it goes back to the beginning
of the solar system, before the Sun and the planets as we know them existed.
A vast disc of gas and dust swirled around a developing Sun. Countless small
objects in the disc collided and stuck together, gradually growing into
larger bodies: the planets.

A record of some of that primordial material is preserved inside certain
meteorites. They are tiny glassy beads, melted dust grains from the original
solar disc, and these chondrules, as they are called, remained virtually
unchanged since that time, almost 4.6 billion years ago. Some of the
smallest things in the exhibition can be the most fascinating.

Dr. Ebel called attention to what he called "the oldest rocks found in the
solar system that we know of." These are not rocks in the usual sense, but
crystals that condensed as the early solar disc began to cool. On display is
a meteorite specimen containing these crystals of calcium and aluminum. They
are 4.568 billion years old, he said, and have not changed significantly
since their creation.

In a circle around the looming Ahnighito, the entirely new displays are
arranged like chapters in a book of solar history. The chapters, or
sections, illustrate what meteorites reveal about the origin of the solar
system, then the formation of planets. A small theater, where one can rest
the feet, shows a video of meteorites narrated by Sally Ride, the first
American woman to fly in space.

The last section addresses the hazards of things falling out of the sky. We
know by now that an asteroid or comet struck Earth 65 million years ago and
did in the dinosaurs. A diorama in the exhibition is a model of the crater
gouged out by an 80-foot-diameter iron meteorite - small by comparison to
the one in the dinosaur event - that struck Arizona about 50,000 years ago.
The impact left a hole in the landscape three-quarters of a mile wide,
called Meteor Crater and also known as Barringer Crater.

A more recent and proximate meteorite impact occurred in 1992. A greenish
fireball streaked across the sky from Kentucky eastward, delivering a rocky
object roughly the size and shape of a football onto the roof of a Chevrolet
parked in Peekskill, N.Y.

Meteorite bombardment was more common and devastating in the early solar
system, as anyone can see by looking at the scarred face of the Moon. Today,
meteorites are near the bottom of the list of life's risks. Hollywood
notwithstanding, Dr. Ebel said, "Never in human history has anything really
big hit our planet."

The only recorded fatality was an Egyptian dog that had the bad luck to be
in the wrong place at the wrong time in 1911. Seven decades later,
scientists recognized that the dog has been struck by a meteorite from Mars.
A piece of Mars, it seems, had reached Earth well before our spacecraft ever
got to Mars.
Received on Fri 19 Sep 2003 12:28:54 AM PDT