The samples were moistened with a radioactive carbon and incubated for up to ten days to allow for any microorganisms to consume the nutrient and give off radioactive gases, which could then be measured.
"The data was clear," said Levin. "The experiment, as designed, performed in a manner that everyone before the mission agreed indicated the presence of life."
But before announcing that life had been found on Mars, NASA conducted more experiments, searching for evidence of organic matter. Nothing was found. This presented a serious problem. Living organisms are made of organic materials. If there is no organic material, there can be no life.
"NASA opted for the easy way out, that there's no life on Mars," said Levin.
He now charges that the organic analysis instrument used by NASA for the Viking expedition was too insensitive, requiring millions of microorganisms to detect any organic matter. It even failed to detect organic material on Earth in some instances, said Levin.
Since the Viking experiment, Levin has focused much of his Mars research on the question of water. The first evidence of liquid water on Mars came from Levin's analysis of temperature measurements made on the footpad of Viking Lander 2. He noted that the soil temperature's rise with the sun halted at precisely the point at which ice turns into liquid water.
A few years ago, Levin's son, Ron, a physicist at MIT's Lincoln Laboratory, helped his father develop a theoretical model showing how liquid water occurs on Mars. The validity of the model was then verified in experiments conducted by scientists at the University of California at Berkeley.
"There's no doubt there's water on Mars," said Levin.
Two out of three missions to Mars have ended in failure, including the Mars Polar Lander, which crashed on the planet in late 1999. Scientists call it the curse of Mars.
A European mission to Mars, the Mars Express orbiter, carrying the lander Beagle 2, was successfully launched from Kazakhstan last Monday.
But the first of two NASA missions, scheduled for Sunday, was postponed due to bad weather. It was launched successfully yesterday. A second exploration rover is scheduled to be launched by NASA later this month. There is also a Japanese mission to Mars.
The timing of the launch is critical, as missions can only occur when planets are in the correct alignment. Right now, Mars is as close to Earth as it will get. The European and U.S. missions will arrive on Mars in January, 2004.
The European explorer will focus on finding water, while the American rovers will be looking at the geochemical composition of the planet's surface.
"The instrumentation onboard these rovers, combined with great mobility, will offer a totally new view of Mars, including a microscopic view inside rocks for the first time," said Ed Weiler, associate administrator for space science at NASA headquarters in Washington.
Levin, however, is critical of the latest missions, saying they will not answer the fundamental question of whether or not there's life on Mars.
"There's no life detection experiment on any of these expeditions," he said.
Levin says he has a new life-detection experiment that could settle the issue, but NASA declined to include it on its mission.
"NASA is afraid to re-examine the data," said Levin. "If it is proved wrong, these people would have egg on their face."
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