[meteorite-list] Cape Charles Embraces Its Crater History

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed Jul 7 20:39:59 2004
Message-ID: <200407080039.RAA08244_at_zagami.jpl.nasa.gov>

http://home.hamptonroads.com/stories/print.cfm?story=72693&ran=177313

Cape Charles embraces its crater history
By DIANE TENNANT
The Virginian-Pilot
July 7, 2004

CAPE CHARLES - From outer space, it's impossible to see the educational
sign at the corner of Bay and Mason.

But from the Victorian heart of town, the opposite is true. The
extraterrestrial is in plain view, right there on the sign. Go just
beyond "the hump," as the railroad overpass is known, and it's under foot.

Scientists with the U.S. Geological Survey and other agencies dug
recently into the Chesapeake Bay impact crater, which was gouged out by
an object from space 35 million years ago. They found a wealth of
information in the rocks but something less tangible, too - a warm
welcome in town.

Cape Charles, from the tourist marker to a proposed museum/research
center to a hotel bar named Ground Zero, has embraced its ancient
history as a tourist attraction.

It's a match made, literally, in the heavens. Wright Horton is a
mountain man.

His specialty at the USGS is the Appalachians, but the 2,900-foot hole
drilled into the crater was expected to penetrate beyond coastal-plain
sediments to the ancient bedrock from which the mountains climbed.

"This is the last frontier for Appalachian geology," Horton said, "the
part that's buried under the Atlantic coastal plain and the continental
margin."

Coreholes drilled over the past several years have sampled the outer
parts of the 56-mile-wide crater. The Cape Charles hole was near the
crater's central peak.

"We're pretty sure we see something that looks like impact melt," said
Ward Sanford, one of the principal investigators on the drilling.
"That's like finding the holy grail."

They do not expect to find actual pieces of the object that made the
crater, but minerals can give clues to what it was - an asteroid, a
comet or a meteor.

Examining the rocks may take several months. One type of chemical
analysis involves irradiating samples in a nuclear reactor, then waiting
six months before looking at them.

"We're still trying to figure out what we have," Horton said. "Some
people describe this as one of the best preserved craters in the world.
The downside of that is that there are no surface outcrops."

Most of the crater is deep under the Chesapeake Bay, but it also
underlies part of the Eastern Shore, the Middle Peninsula and Hampton
Roads.

The drill ran day and night for several weeks, lubricated by drilling
mud that poured into the hole and was pumped back out. Scientists had to
sit by the drain pipe and sift the mud for rock and fossils.

"I was on the night shift, 5 p.m. to 5 a.m.," Horton said. "I don't know
whether 12 hours sitting by a horizontal pipe catching mud sounds
exciting to you, but it actually did get kind of exciting as we got
deeper and started seeing things we hadn't seen before." Dave Daniels
does gravity.

While gravity may seem constant, it is not. A person standing on the top
of Pikes Peak would weigh slightly less than the same person standing at
sea level, Daniels said. Dense rock has more gravity than shattered
rock. The crater is filled with rocks that were blown out during impact
and then fell or washed back in.

A high gravity point seems to indicate the crater's central peak. More
mysterious are two other points of high gravity, which could mean lesser
peaks, which could mean the object that made the crater broke apart
before impact and actually hit separately.

Magnetic readings also are helping scientists map the shape of the
crater more accurately for studying groundwater and future drilling.
Deep rocks were magnetized during the impact, but in a slightly
different orientation to Earth's current magnetic field.

"The work is in progress," Daniels said. "Somewhere below Cape Charles
is this central peak that everybody is sure is there and the gravity and
the magnetics seem to indicate it is there, but are we going to see that
in those samples we brought back? I don?t know the answer to that."
Sanford himself is after water. The main purpose of the drilling was to
create a well where samples could be taken at different depths.

The state Department of Environmental Quality is charged with regulating
groundwater use, but it doesn't have a clear picture of what the water
is like inside the crater or how much is there. Much of the Eastern
Shore lies over the crater, and new houses are going up every day.

So far, the well has yielded water with 47 parts of salt per thousand
parts of water. Seawater has only 35. But the well also produced water
with only 10 parts per thousand. It is unusual, Sanford said, to find
fresh water so close to brine.

It could mean that water moves more easily through the crater fill than
once thought.

Sanford also will look for helium. Helium-3 is found in certain types of
asteroids, and high amounts of helium-4 would indicate that water had
remained in place for a long time.

Pictured are core samples from the Chesapeake Bay impact crater that
were collected by scientists in Cape Charles. The crater was gouged out
by an object from space 35 million years ago.

He also will try to figure out why water at the bottom of the hole was
100 degrees Fahrenheit. Most likely, he said, the drilling mud was hot
when it was pumped in.

"We think there's no way there's residual heat from the impact itself,"
he said. "Every time we try to answer questions, we raise more
questions." Mary Voytek is not, repeat not, looking for aliens.

"For me, it's a bit of a fishing expedition," said the microbiologist.
"People have long been interested in the idea of impacts and impact
craters as sort of the origin of life, that these impacts created
hydrothermal environments."

Deep-sea explorers have found thriving colonies of bacteria that live on
volcanic vents, under incredible pressure and heat.

The crater impact could have created similar environments.

"The intense heats would have sterilized anything around it," Voytek
said. "As the system began to cool, you could have biotic synthesis.
We're hoping to see if there's any evidence of cells still remaining,
either active or preserved."

The difficult part is preventing modern-day surface bacteria from
contaminating the rock samples. Pieces were flash-frozen in liquid
nitrogen, and Voytek will probe into their centers in search of pristine
material. Then she will test for DNA.

Because the crater filled with broken rocks that are still settling,
there is plenty of living space for microbes, she said.

"One of the most exciting theories about how life originated on this
planet is it rode in on an asteroid or meteorite," Voytek said. "I'm not
looking for an alien. Things that survive in extreme environments always
look different from an ordinary community, but they're not so different."

"I'm happy to say I don't know what I'm going to find. It's a
discovery." Celia Burge is a happy camper.

As the town manager of Cape Charles, she sees marketing potential in the
impact crater. The town has already obtained money from the Chesapeake
Bay Gateways Program for educational signs that explain the town's
origins, from the crater underneath it to the railroad and ferry that
sustained it.

Gateways, a project of the National Park Service, also could provide
money for an interpretive center, she said.

"When you say museum, that sounds a little stuffy," Burge said. "We
would like to be a leader in helping everybody who lives around the Bay
understand the implications of that meteor and the impact crater that
now all of us live with."

Burge is interested in studies that show ancient river beds wrapping
around the crater. She is concerned about future water supplies and
whether the Eastern Shore will need desalination plants to support its
growth.

A development with houses, golf courses and a hotel/resort is under
construction near the well, with the Ground Zero bar.

The developer and Burge echo the enthusiasm of David Powars, one of the
first scientists to discover the crater.

Powars is thrilled with rock so crumbly that it turns to dust in his
hands, with a possible "shatter cone" that points toward the impact
zone, with all that's left to be discovered.

"This is the coolest," he said. "It's much more complex than anything
we've dreamed of, and we've been dreaming."
Received on Wed 07 Jul 2004 08:39:55 PM PDT