[meteorite-list] New Chesapeake Bay Crater Sample to Look For Saltwater and Source of Impact

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon May 10 13:42:50 2004
Message-ID: <200405101742.KAA05663_at_zagami.jpl.nasa.gov>

http://home.hamptonroads.com/stories/story.cfm?story=70039&ran=120831

New crater sample to look for saltwater and source of impact
By DIANE TENNANT
The Virginian-Pilot
May 7, 2004

The deepest hole yet drilled into the Chesapeake Bay impact crater
will be started Saturday, as scientists begin searching for salty
water and even, perhaps, some remnants of the asteroid or meteor
that crashed there 35 million years ago.

A 2,900-foot hole will be drilled by the U.S. Geological Survey in
the Sustainable Technology Park just south of Cape Charles on the
Eastern Shore. Work is expected to last until the end of May. The
hole will be used primarily as a well for sampling water, but some
rock cores and cuttings will also be retrieved. Most of the other
holes drilled into the crater have been for core samples.

The crater, which is entirely underground, is about 56 miles
across and 1.2 miles deep, centered on Cape Charles. It was formed
by an extraterrestrial object - a meteor, an asteroid or a comet -
that slammed into the Earth at a speed of about 76,000 mph.

The eastern part of Virginia was under water then, and the object
landed in a shallow sea, creating tsunamis that could have topped
the Blue Ridge Mountains.

"Our previous drilling has been in the outer part of the crater,"
said Greg Gohn, of the USGS. "Now we're going to be drilling in
the central crater where all the material was either vaporized or
melted or ejected, and some slumped back in to fill the hole."

Scientists expect to find salty water in the well, but
they don't know how salty. At nearby Kiptopeke, a
shallower well produces water that is saltier than the
sea, indicating that it hasn't moved or been
replenished for millions of years.

"This will help address whether that brine is more
widespread than just at Kiptopeke," said Ward
Sanford, a USGS hydrogeologist. Regional water
managers are interested in where underground
aquifers are located and how fast they are
replenished. Wells drilled in aquifers that don't refill
quickly could run dry.

Sanford said that scientists will analyze water and
rocks for helium, which forms from the decay of
uranium.

High amounts of helium-4 indicate that water has remained
in the same place for a long time, and the amount of helium-3,
which is found in certain types of asteroids, could help
determine what exactly formed the crater, he said.

"We might get lucky and find some impact melt," he said.
"They could find traces that suggest part of the original
impactor was melted and mixed in. It could be that it all
vaporized."

The hole will also lay some groundwork for a proposed
international project. The International Continental
Scientific Drilling Program is considering a request to
fund a 7,000-foot hole drilled into the center of the crater.
Received on Mon 10 May 2004 01:42:38 PM PDT