RELEASE NO: 98-169

NASA SCIENTISTS TO STUDY POSSIBLE IMPACT CRATER

Students to take "virtual field" trip via Internet

Scientists from NASA’s Goddard Space Flight Center leave for a scientific expedition to a possible impact crater in northern Bolivia on Oct. 14. Hidden in the dense jungle, the circular feature seen in a satellite photo could represent one of the youngest, large-scale hyper-velocity impact craters ever found on Earth.

Scientists discovered this five-mile-wide feature, known as the Iturralde Structure, 10 years ago by using Landsat Thematic Mapper satellite images of this portion of the Bolivian rain forest.

The Goddard science team will be trying to determine if the Iturralde feature is the surface expression of a meteorite impact crater in the water-sogged soils of the remote jungle.

"We haven’t seen events of this magnitude in the Earth’s geological record very often in the last million years," said James Garvin, a Goddard geologist and impact expert who also studies craters on Mars. The possible Bolivian crater sits in soft sediments that are approximately 20,000 years old, according to Garvin.

Peter Wasilewski, a Goddard meteorite scientist said that craters on Mars or in the Earth’s deserts, such as the 50,000-year-old Meteor Crater in northern Arizona, which is one-eighth the diameter of the Iturralde feature, are easy to see and study in detail. But in tropical environments, rain, rivers and floods act as giant erasers, wiping out the traces of meteor impacts. "So we have a challenge," said Garvin. "How does one prove this is a crater?"

Initial evidence from the satellite image shows a prominent sub-circular ring of forest surrounding an area of low-lying grasslands, and, in the center, a higher area covered by trees. The shape of the structure is typical of impact craters that rebound in the center after impact and form a rim around the edges.

But to prove the image seen from space is an actual hyper-velocity impact crater formed by a colliding meteor, scientists must find evidence on the ground. The team will look at how soils differ inside and outside the crater area, check if the feature has different magnetic properties than the surrounding area, and look for any rocks that may have recorded evidence of an explosive collision.

According to Garvin it would take a 10,000 megaton explosion to make a crater the size of the Iturralde Structure. Such a large meteor impact could change climate by reducing temperatures in the same way as large volcanic eruptions.

Compton Tucker, a Goddard biologist who works on the effects of deforestation with both satellite images and on the ground, has flown over the target area. He found that even from an airplane, the large crater is hard to see as a whole, but differences in vegetation offer evidence of a slight depression that could have been caused by a meteor impact. Tucker and several other biologists and botantists from the University of Bolivia will join the expedition to study the biodiversity in the remote area.

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Note to Editors/News Directors:

Students from around the world will be able to follow the expedition in South America via the Internet.

Joining the scientists on the 10-day journey is Tom Albert, a Howard County, Md., science teacher who is on assignment at Goddard. He will bring hundreds of students along on the exploratory impact crater reconnaissance mission live via the Internet.

Albert will conduct 30-minute interactive educational sessions and answer questions posed by Maryland junior high and high school students. Participating schools have been selected based on the NASA Goddard Ambassadors Program, which allows teachers from Maryland schools to train at Goddard in the use of computer technology to enhance their instruction of Earth science in the classroom.

"This expedition to the Amazon is just the tip of the educational iceberg," stated Albert. "The potential to provide teachers with more "wow factor" for their students is tremendous. To think that we are working with NASA to bring this discovery live to students truly brings new meaning to the concept of hands-on education."

While the Goddard science team works on science in the field, the students will replicate the mission back home, digging soil pits and interpreting satellite images. Students will examine the physics behind the crater formation, the biodiversity of the area, soil samples and magnetometer readings.

Although only the NASA Goddard Ambassador schools will be able to participate live via the Internet, other schools and home-schooled students, as well as the general public are encouraged to watch and follow the activities as they happen. The science plan for this expedition was written by NASA Teacher Ambassadors and can be found at:

http://pao.gsfc.nasa.gov/gsfc/bolivia/bolivia.htm

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