The Search for the Missing Amazon Meteor

The Araona people wanted $1 million before they would let the NASA ( news - web sites) 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.

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.

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.

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.

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.

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).

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.

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.

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."

"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."

Imagine that.

Thank you for posting the most interesting articles! I appreciate reading something other than politics occasionally, and you always have the best science anad archaeological articles. Thanks again!

Ooops! I see SteveH posted this one! Well, blam is the best, but Steve has done a good job with this one. <p.Now i will remain quiet and slink away....

Tree rings and ice core samples have recorded worldwide catastrophic events at, 3195BC, 2254BC, 1628BC, 1159BC and 540AD. (Pick one)

the largest hydrogen bomb ever detonated had the power of one megaton of dynamite

The largest was in fact a 50 megaton bomb dropped by the USSR
on 31 Oct 1961 over Novay, Zemlya. It was given the Tzar Bomba.

Sounds like taking a "salt lick" of sorts to attract the bugs away from the workers might be handy.

It was given the Tzar Bomba

Oops. It was given the name "Tzar Bomba"

Thanks for the plunk. I wonder if perhaps a meteorite might have impaled rather than exploded in soils that deep. If the magnetometers see it, they may end up able to pay those natives their million bucks and then some.

"I wonder if perhaps a meteorite might have impaled rather than exploded in soils that deep. "

Yup. They were describing it in unusual terms.

"Thanks very much for those relevant and interesting article links!"

You're welcome. It plays into my idea of things, I'm a catastrophist

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