CLUES FROM THE RED PLANET AUGUST 7, 1996 TRANSCRIPT

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NASA scientists have discovered chemical and mineralogical evidence suggesting single-celled organisms once existed on Mars. The discovery raises new hopes of life on other planets. Kwame Holman has the details on the Martian meterorite that has the scientific community buzzing.

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NewsHour Links: August 7, 1996 Jim Lehrer talks to scientists about the implications of the Martian meteorite. July 10, 1996 Jeffrey Kaye looks at the moons of Jupiter External Links The Johnson Space Center Check out recent pictures of Mars.

KWAME HOLMAN: The possibility that life once existed on Mars has been substantially bolstered by the discovery of organic compounds in a meteorite that plunged from Mars to Earth 13,000 years ago. At a packed news conference at the headquarters of the National Aeronautics & Space Administration in Washington a team of scientists led by David McKay discussed the findings.

DAVID McKAY, NASA, Johnson Space Center: We have these--these lines of evidence, and none of them in itself is definitive but taken together the simplest explanation to us is that they are the remains of Martian life.

KWAME HOLMAN: Thought not conclusive, the discovery made for a fascinating detective story for researchers. In thin slices of the meteorite, they found organic molecules called polycyclic aromatic hydrocarbons or PAH's. The molecules are believed to be evidence of ancient single-cell life. Under an electron microscope, the researchers found oval-shaped particles called magnatites whose chemistry is similar to magnetites produced by bacteria on Earth.

KATHIE THOMAS-KEPRTA, Lockheed-Martin: We can actually determine based on the literature and based on three criteria if this magnatite that we're seeing is biogenic or not, whether it's been produced by bacteria based on the distinctive shapes, based on the chemistry, and based on the environment. Now these shapes--next slide--these shapes are very similar to magnatite that's produced from bacteria on the Earth.

KWAME HOLMAN: According to the team, those primitive organisms or micro-fossils, were deposited in the rock 1 billion years after it was formed on Mars 4 ½ billion years ago. The meteorite was discovered in Antarctica in 1984 but only recently identified as Martian.

The scientists estimate a huge asteroid collided with Mars about 15 million years ago and blasted rock from Mars into space, where it wandered until it fell onto an ice field in Antarctica some 13, 000 years ago. Scientists say they're fairly convinced the micro-fossils they found were in the rock before it got to Earth.

RICHARD ZARE, Stanford University: We find them more on the inside of the rock than on the fusion crust. We believe that means that they're indigenous, they belong to the rock. If they came from a contamination that came through the rock, while it was on Earth, it would really expect to be more on the outside working its way in. It's completely backwards as to what we find.

KWAME HOLMAN: Life on Mars has been considered a possibility ever since it was learned water once existed on the planet's surface, but landings by Viking spacecraft during the 1970's revealed no sign of life. Team members were asked how this discovery felt.

EVERETT GIBSON JR., NASA, Johnson Space Center: One evening when we were on the electron microscope, looking around on the sample, and we came to this segmented structure, and, uh, that caught our attention, and we began to ask each other, is this for real, and I can honestly say that even when I went home I had difficulty sleeping because of the thoughts of what this could be, and I still wonder are we sure that this is a segmented structure, is it indigenous to sample, and I've come to the conclusion yes, it is, and there are other tests that we want to do, and, you know, we're really excited about getting in this project, and it's undoubtedly the most exciting thing I've done in my 27 years as a scientist.

KWAME HOLMAN: As the scientists prepare to follow up on their discovery, the President today announced a summit conference this year on the future of the space program.

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