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KNOXVILLE, Tenn. — A University of Tennessee microbiologist is helping NASA make sure any life found on Mars didn’t hitchhike from Earth on a dirty spaceship.

Dr. David White has been named a visiting scientist with NASA’s Planetary Protection Project at the Jet Proplusion Laboratory in California. He also will help NASA make sure organisms brought back for study do not spread and disrupt Earth’s environment.

White will develop methods to prevent microbes on Earth spacecraft from contaminating Martian soil and rock samples. NASA’s next Mars landing is planned for December, 1999.

”We want the discovery of life to be unequivocal,” White said. ”We want to be sure what we find is indeed life from another planet. That is why it is so important not to have any contamination.”

White, a UT-Knoxville-Oak Ridge National Laboratory Distinguished Scientist, also will work to prevent samples returned from Mars from contaminating Earth.

”There is a huge debate over whether we should kill a living organism before bringing it back to Earth,” White said. ”My personal thought is that we should not return it to Earth alive because of the remote possibility that it could spread like kudzu and damage our ecosystem.

”It first should come back to a space station or a moon station or be sterilized.”

The space agency plans to bring Martian soil and rock samples to Earth in 2008, White said.

White will work at NASA’s Pasadena laboratory on all aspects of the latest Mars spacecraft — from construction and assembly to liftoff — looking for microbial contamination and ways to eliminate it.

He has studied microbial life in Earth’s most hostile environments — from volcanic cracks in the ocean floor to frozen Antarctic deserts. Some microbes could survive a trip to Mars and contaminate samples collected there, he said.

Bacterial contamination levels for Viking, NASA’s 1976 Mars mission, were measured in hundreds of microbes per square centimeter, he said. Modern microscopy techniques allow a closer look and may help further reduce contamination, White said.

”It is vitally important to clean and protect the spacecraft from Earth contamination before it lands in those crucial areas of Mars where water once existed and where we will look for specific biological signs of life,” White said.

Dr. Kenneth N. Nealson, senior astrobiologist at JPL, said intense heat used to decontaminate on the Viking mission would destroy sensitive instruments on today’s spacecraft.

Ethanol and mechanical scrubs were used to cleanse NASA’s Pathfinder spacecraft which landed on Mars last year, but White said he will be searching for more thorough cleaning methods.

”Fifteen percent of Viking’s costs were from developing electronics that could withstand the high sterilization temperatures,” Nealson said. ”There just isn’t money to do that these days. We must develop new methods to detect and eliminate contaminating organisms.

”Obviously, a clever scientist like David White is a great asset when you’re trying to do that.”