Change in paradigm
Albeit a great discovery if future Mars craft uncover Martian biology, the case can be made that Viking succeeded in that task a quarter of a century ago.
Viking clearly found life. That is the steadfast belief of Gilbert Levin, former Viking scientist and now chief executive officer for Spherix in Beltsville, Maryland. It was his Labeled Release experiment that, he claims, detected microbial organisms in the Martian soil.
One of three Viking biology investigations conducted on Mars, Levin's technique used a sample of Martian soil stirred in with a nutrient "soup" containing radioactive carbon-14. If living organisms were in the soil sample, they would digest the radioactively-labeled nutrients, then give off gases indicating the presence of life metabolizing the nutrient.
On Mars, the Viking assay detected a surge in the radioactivity of released gases.
Those results remain not only puzzling, but controversial as well. Some Mars biologists have said that a nonbiological response was observed. NASA's official analysis is that the Viking experiments found no evidence of life at either landing site, but the data didn't rule out the possibility that life may have existed in the past or may still exist in other, more hospitable places.
"The Viking landing sites are extremely dry desert environments where it would be unlikely to find present-day biological activity on the surface," said Jim Garvin, Mars program scientist at NASA Headquarters.
"Other sites on Mars, such as nearer the polar caps or other places where liquid water may be found, are far more likely places to look for signs of present or past life. Our long-term plans call for missions to find liquid water on or under the surface, which will be the best places to begin a search for signs of life."
Levin disagrees, of course, with NASA's agnostic analysis of the Viking data.
"It's extremely unlikely that there are no living organisms on Mars," Levin maintains. "It's now very unlikely that Mars could be sterile. If from no other place, it has received living organisms from Earth, sprayed into space by impacts on our planet. The situation on Mars would allow those organisms to continue to grow and thrive," he said.
Levin has been busy at work on a surprising new find, buried in the Viking data itself. Details are forthcoming, he said, to help "start the long-needed change in paradigm to one accepting life on Mars."
Organic matter
In the camp of giving Levin's Labeled Release results a second chance is David Warmflash, an astrobiologist at the Johnson Space Center. "It takes a while for people to go back and rethink these things," he said.
"For some reason, there are a lot of people very uncomfortable with the idea of Mars having life. I can't explain it exactly," Warmflash told SPACE.com.
Work done on Martian meteorites, Warmflash said, show that organic matter is likely present in Mars' crust. If true, the interpretation of Viking biology experiments may need to be reevaluated, he said.
Moreover, Levin's results have not been totally replicated using non-biological means, Warmflash said.
Inorganic and biological explanations for Levin's Viking data, Warmflash said, "should now be considered equally plausible until more complete studies of the Martian surface are carried out."
The Viking biology experiments should be seen "not as failures for their inability to provide unambiguous evidence for or against Martian life, but as a foundation for the development of future life-detection instruments," Warmflash concludes.
Mars: off limits?
Many believe that, decades hence, Mars is sure to come under the heels of human explorers.
But what motivations must be aligned to hurl people instead of payloads to the Red Planet?
The answer is tough to find, said David Portree, author of a new NASA book, Humans to Mars: Fifty Years of Mission Planning, 1950-2000. He is also a public program staffer at the Lowell Observatory in Flagstaff, Arizona.
"I still haven't fully identified in my mind why we need humans. When push comes to shove, I'm perfectly happy right now sending robots. They are far cheaper and send back good information," Portree said. If going to Mars is "merely" a scientific pursuit, he expects the level of tolerable risk will be very low -- much less than Apollo which benefited from Cold War motivations to beat the Russians.
"Mitigating risk will cost more money than accepting risk," Portree said.
Then, there's the question of life on Mars.
Portree feels that finding Martian biology could short-circuit societal interest in dispatching humans to Mars. A growing environmental passion here on Earth might spur a declaration that Mars be "off limits," calling to question human crews traipsing over a biological work-in-progress, he said.
"I'm concerned that if you send people, you can't really help but contaminate the place," Portree said.
Right now, the first piloted Mars mission could be more than 20 years away, Portree senses.
"But history shows the foolhardiness of prognostication," he said. "Could we have guessed in 1929 that humans would be on the Moon in 1969? Could we have guessed in 1961 that humans would not be on Mars in 2001?"
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