[meteorite-list] The Search For The Missing Amazon Meteor

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:08:30 2004
Message-ID: <200209241738.KAA23917_at_zagami.jpl.nasa.gov>

http://www.space.com/scienceastronomy/planetearth/crater_expedition_020924-1.html

The Search For The Missing Amazon Meteor
By Diana Jong
space.com
24 September 2002

The Araona people wanted $1 million before they would let the NASA
scientists pass through their territory in the remote Bolivian Amazon. Given
a budget of $20,000 for their entire expedition, the scientists resorted to
negotiating, and the indigenous people eventually agreed to a payment of
$500, plus 500 rounds of .22 ammunition and 200 D-cell batteries.

"They couldn't be Eveready; they had to be Rayovac," recalls Compton Tucker,
an earth scientist from NASA's Goddard Space Flight Center.

Unfortunately, the discussions stalled the group a week and by the time they
reached the Iturralde Crater in October 1998, the rainy season had started
and flooding prevented them from completing their research.

Four years later, Tucker and his colleagues have returned to the site to
finish their work. This time, he says, "we know what to expect."

In an interview in early September before he left for Bolivia, Tucker said
email reports from the pre-expedition negotiations with the Araona indicate
that they want a motorized canoe, two extra motors and an office, rent paid,
in the nearby town of Riberalta.

The price is worth it to Tucker and the other researchers on the expedition,
in full swing this week, because of the significance of the questions they
could answer.

Unknown cause

Scientists are not certain how or when Iturralde Crater formed (despite its
name that alludes to an impact). General speculation and circumstantial
evidence point to the collision of a meteor - either an asteroid or comet --
about 5,000 to 30,000 years ago. This would make it one of the youngest
impact craters known, although some scientists argue it is much older.

If the crater is young, it may correlate to climatological events in Earth's
history or to a known extinction event. It may even be included in the
folklore of some South American native tribes.

"Or it's just an odd, perfect round hole on the face of the Earth and you
have to start thinking about extraterrestrials or something," jokes Tim
Killeen, a conservation biologist who will lead the trek.

Killeen, a research fellow with Conservation International, has been living
in Bolivia and working with the Noel Kempff Mercado Natural History Museum
in Santa Cruz for about the last 18 years. He first met Tucker when, he
says, "about seven or eight years ago, these guys from NASA started coming
down and bothering me to help them interpret their satellite imagery."

Despite Killeen's familiarity with Bolivia, the expedition team needs the
assistance of the Araona to reach the Iturralde Crater, not just to pass
through their land, but to serve as guides. The locals will also help blaze
the 9-mile (15-kilometer) trail to the crater, which caps a trip involving
rides in a jet, a motorboat, a dugout canoe and a helicopter (courtesy of
the Drug Enforcement Agency).

But it isn't the crater's remote location that contributed to scientists'
late identification of Iturralde as a possible impact site in 1985. Rather,
its features are very subtle.

Unlike Meteor Crater, a gaping hole 550 feet (170 meters) deep in the
Arizona bedrock, the elevation at Iturralde changes by no more than the
height of a small child. It is difficult to spot in an area that spans 5
miles (10 kilometers). Yet a nearly perfectly circular pattern, due to
differences in vegetation, stands out in Landsat images taken from space.

Washing away evidence

Iturralde's subtle features may be due to its location. Erosion is quick in
the wet, rainforest environment.

If the crater is still visible, some scientists say, it cannot be much older
30,000 years; otherwise it would have completely eroded away.

The challenges in identifying the crater are many. The soil in rainforests
is very deep. There is about 2 miles (3 kilometers) of it covering the
bedrock that's under Bolivia. An impact would have ejected that material
into the atmosphere, but some of it would have slumped back into the
temporarily gaping hole over time.

"It was more like a big splat," Tucker says, in reference to other impacts
that expend most of their energy blowing up bedrock.

All this makes the researchers' job more difficult. They will still search
for the usual, expected rocks and glass particles (called shocked quartz)
associated with impacts, but this material may have eroded away. The
scientists will take soil core samples to analyze for increased levels of
elements that are found in more abundance in meteors than on Earth. One of
these, iridium, can help distinguish whether a space rock was a comet or
asteroid.

Canoe science

There are other subtle clues to look for. The impact might have displaced
ancient, extremely deep layers of soil, or paleo-soils, and placed them at a
higher level than normal.

"If there was this big explosion," Killeen explains, "there would have been
a big splash, so that splash should have slopped over a lot of soil to the
areas adjacent to the crater."

Three or four meters of newer soil that was formed since the impact would
then cover the displaced paleo-soils. Scientists will float the river in
motorized canoes searching for areas where water cuts into the riverbanks
and the paleo-soils might be revealed. Dating the paleo-soils and the soil
levels that sandwich them can also narrow down when the impact occurred.

Killeen will also participate in the biologists' efforts to collect samples
of the flora and fauna in and around the crater. Besides contributing to
their understanding of the region's biodiversity (which is Killeen's primary
work for Conservation International) they are trying to characterize the
subtle differences in vegetation detected by Landsat.

But perhaps what would be the most compelling evidence of an impact is not
in rocks or shocked quartz or flora, but in data showing changes in the
magnetic field.

Big as a bus

To make a crater the size of Iturralde, the impacting object would be
roughly the size of a bus and the event would release energy equivalent to
thousands of megatons of dynamite, according to James Garvin, an impact
crater expert at NASA. In comparison, the largest hydrogen bomb ever
detonated had the power of one megaton of dynamite.

"The global impact would have been equivalent to that of a large volcanic
eruption, like Pinatubo," Garvin says.

Dust could have been carried through the atmosphere and deposited in places
as far away as Greenland, the Andes mountains, or even Antarctica. Any data
gathered at Iturralde can then be correlated with ice cores taken at these
frozen locations.

But on a local level around the blast, the energy released would heat the
surrounding dust and material to a plasma-like state. As the material cools,
the magnetic field realigns differently from the original direction and can
form a conspicuous pattern distinct from the underlying magnetic field of
the Earth.

"It's like if you drop a pebble in the water and you see the waves coming
out, with rings that define different magnetic measurements," says Patrick
Coronado, a senior engineer at Goddard.

Miniature Cessna

Coronado led the team that developed the MagPlane, or Magnetometer Plane, a
one-third-scale Cessna with a 12-foot wingspan, fitted with a highly
sensitive hand-made magnetometer. "The same quality and sensitivity as
spacecraft magnetometers," Coronado says. It runs on a modified weed-whacker
engine that should power the 44-pound plane for three hours on a half-gallon
of standard gasoline. "Trying to get special fuel down there is not trivial
so we had to use the regular stuff."

Each MagPlane cost about $50,000 to make. The first one went from concept to
finished product in six months. "Even if we had all the money in the world
it wouldn't really have helped because a lot of it was new," Coronado says.

The MagPlane was born when Tucker and the expedition organizer, Peter
Wasilewski, a Goddard astrophysicist, were consulting with Goddard's Office
of University Programs, which provided most of their funding through the
director's discretionary fund, about maximizing their magnetic field
measurements.

"The [University Programs] office is just down the hall from me," Coronado
says. They told Tucker and Wasilewski about "this guy down the hallway who
has little planes for remote sensing, so they perked their ears and opened
their eyes and came down and talked to me," Coronado recounts. "This was six
months ago, and we started working the next day. We were behind schedule the
day after we started."

Coronado says the project was similar to the Skunkworks, "like the old days
at Lockheed when you crammed a bunch of engineers in a room and you put food
and water under the door and they worked until they dropped."

When Coronado spoke with SPACE.com, he and his team were still constructing
the magnetometer for a backup MagPlane. "My engineer is taking it down with
him to install on the second plane in case the first one goes down.
Otherwise all there is is a pretty plane flying around taking pictures."
Because of the tight schedule, however, the MagPlane has not been fully
tested. "A lot of the testing will occur as it's doing its job."

Still, the MagPlane is more than was originally planned. The trek was
supposed to start last fall but was postponed because of the terror attacks
last year.

The expedition officially started this year on Sept. 10, and the MagPlane
flight is scheduled for Wednesday, Sept. 25. In case it doesn't work out,
the scientists have also brought along ground-based magnetometers.

On Sept. 26, the expedition team will hold their third and last live
webcast, accessible through their web site (http://www.blueiceonline.org).

Reaching out

One of the main functions of the website, besides entertaining interested
Web surfers, is to link the scientists in Bolivia with teachers
participating in an educational outreach. Called "Teacher as Scientist," the
program involves educators at home in the scientific process, working
alongside the researchers to determine what kind of data will be gathered in
the field. There is even one teacher-scientist on the expedition team.

Students can follow the expedition through the live webcasts and daily
updates. A worksheet has also been posted as a classroom resource.

The educational component of the expedition is a result of the funding
provided by the Office of University Programs. But there are also those not
financially invested in the expedition who are very interested in the
results.

Legends of fire

Last month, scientists at the "Environmental Catastrophes and Recovery in
the Holocene" conference in London discussed the high incidence of disaster
and fireball legends in the areas of South America, including Bolivia.

The Iturralde Crater, if it was made by an impact, could be an explanation,
says Benny Peiser, a social anthropologist from Liverpool John Moores
University.

"If there was an impact in the last 10,000 years, then the logic would be
that the survivors would be talking about it and including it in their
traditions and legends," Peiser says. "If this proves to be an impact crater
of a very young age, then this could have enormous consequences for our view
of societal evolution and potentially might answer a lot of questions in the
history of South America."

Garvin has studied impact craters, including Iturralde, while at Goddard,
but he is now NASA's lead Mars scientist. There are no plans to send an
expedition to study impact craters on Mars, so the Bolivian trek is as close
as Garvin will get. Even though the environments on the two planets are very
different, the soft, dusty soils may be similar.

"There are a lot of these real subtle impact features that look like
Iturralde, with no trees, on Mars," Garvin says. "Studying craters on Earth,
we can get up close and personal with them; it's the only way we're going to
understand what we have on a planet like Mars."

Garvin, who has traveled to exotic places including Kazakhstan to study
impact craters, is not a part of the expedition and so awaits the data from
the comfort of his office in Washington D.C.

"I'll be frank," he said. "I've been to many impact sites on this planet and
I find that my talents are better in the cold, dry environments. That's part
of the reason why I work on Mars. Compton is the type of guy who does real
well in the jungle."

This trip will be Compton Tucker's seventh or eighth Amazonian voyage. They
seem almost natural to him as he calmly describes the jungle lifestyle he
will lead. The team members eat two meals a day, prepared by a cook they
hire, of rice and beans supplemented with fish they catch and things they've
brought from home. The menu ranges from piranha to beef jerky.

Social bugs

The team's base camp consists of tents pitched along a river in Puerto
Araona, the main village of the Araona people, population: 110.

"And it'll be hot and humid and there will be a lot of insects," Tucker
says. "One of the big problems which most people don't realize, in all the
tropical forests I've been in, there isn't much salt because it rains so
much it would tend to wash it away. The social insects view sweating people
like us as a great salt lick, so the social insects will communicate to
other social insects where you are and so after two or three days, there
will just be, as soon as the Sun comes up, hundreds if not thousands of bees
and wasps who want to just land on you to get the salt. And of course there
are a lot of mosquitoes."

But Tucker is not intimidated.

"Some people freak out but that's just one of the things you have to
endure...You just have to keep moving and every day you have to bathe, so
you just get in the river and wash and you also wash your clothes because
you want to get the salt out."

Killeen, who has led at least 15 Amazonian expeditions, has an equally
optimistic outlook. "I think it's going to be a great time," he says. "I'm
looking forward to swinging a machete instead of thinking about traffic."

For others, though, it's not the fear of insects or the primitive living
conditions or even sometimes-stubborn indigenous people that keep them from
the Iturralde Crater.

"I'd like to go," says Coronado, the Goddard engineer, "but my wife wouldn't
let me."
Received on Tue 24 Sep 2002 01:38:24 PM PDT