http://www.space.com/news/spacehistory/viking_life_010728-1.html
WASHINGTON -- There is new life in old data…and it's likely Martian life.
Several scientists have found compelling evidence that Viking Mars landers did indeed discover life on the red planet in 1976. A re-examination of findings relayed to Earth by the probes some 25 years ago, claim the experts, show the tell-tale signs of microbes lurking within the Martian soil.
The researchers will unveil their views Sunday, July 29, at a session on astrobiology, held during the SPIE's 46th annual International Society for Optical Engineering meeting in San Diego, California.
Slam dunk discovery
When the Viking 1 and Viking 2 Landers dropped in on Mars that July and September of 1976, respectively, each carried the same set of biological experiments to search for signs of life.
But over a quarter of a century later, exactly what the robotic twosome did detect remains hotly debated.
The scientific squabble centers on one Viking biology investigation: the Labeled Release (LR) life detection experiment. It used a small measure of scooped up soil, stirred together with a nutrient "soup" containing carbon-14.
The idea was that any living organisms present would digest the radioactively labeled nutrient solution, then belch off gases as life metabolized the nutrient. And guess what? The LR experiments on both Landers coughed up puffs of radiolabeled gas - evidence for microorganisms in the soil of Mars.
But it was no slam-dunk of a discovery.
Sterile Mars
Another Viking experiment, a gas chromatograph mass-spectrometer (GCMS), built to identify organic molecules on Mars, found none to analyze.
That find threw the LR results into question. A default position adopted by a majority of scientists was that no life was present at the Viking sites. What the LR device yielded, said many of those assessing the Viking data, was a false positive result.
Cause of the result, and still widely held: A chemical practical joker is in the soil, some sort of oxidant that fooled the LR experiment.
Over the years, that verdict has been touted by many as the most likely rationale for the LR results. Moreover, that oxidant is nasty to life. It destroys organic materials, causing the surface of Mars to be a sterile, lifeless domain. Therefore, no wonder the GCMS found Mars absent of organic materials.
This tidy explanation has served well to derail talk that the Viking Landers detected life.
Clinging to the magnets
But a staunch believer that Viking found life is Gilbert Levin, former Viking scientist and now chief executive officer for Spherix in Beltsville, Maryland. His Labeled Release experiment, he told SPACE.com, worked like a charm and gave notice that life was observed
"The Viking LR experiment detected living microorganisms in the soil of Mars," Levin flatly said.
Also believing that a biological interpretation of the LR on Mars cannot be dismissed is David Warmflash, an astrobiologist at the NASA Johnson Space Center in Houston, Texas.
Warmflash said that the failure of the Viking GCMS to find organic molecules has been called to question. "More recent findings suggesting that the Viking GCMS would have missed such molecules if present necessitates a re-evaluation of the Viking LR data as well as a continued search for organic material and life at the Martian surface," he said.
At the SPIE meeting in San Diego, Levin said that after years of tests, and over two dozen non-biological explanations later, "none of the many attempts to establish the oxidant's mimicry of the LR data did so," he said.
Furthermore, Levin reported that direct evidence exists against any highly oxidizing substance in the surface material of Mars - tucked away and apparently overlooked in the Viking data itself.
Photos taken on Mars' surface of a Viking magnetic experiment on both landers show material clinging to the magnets. That suggests to Levin that whatever the surface processes are on Mars, they are not innately highly oxidizing. A highly oxidizing soil would convert magnetized materials to oxidized forms. Therefore, the magnet would be free of such particles.
Similarly, the Mars Pathfinder mission in 1997, Levin added, also had significant amounts of magnetic material adhering to magnets attached to the spacecraft.
Levin said that the paradigm of a Mars sterilized by a highly oxidizing surface is "too embedded in our scientific fabric to be set aside even by demonstrated proofs. He points to a John F. Kennedy quote that says "the great enemy of truth is often not the lie --deliberate, contrived and dishonest -- but the myth -- persistent, persuasive and unrealistic."
Infection of Mars
Levin said that the likelihood is high that life, from Earth and elsewhere, exists on Mars today.
The transfer of microorganisms from one planet to another by meteoric impact is gaining increasing support, Levin said. That being the case, "it is now more difficult to propose a sterile Mars than a live one," he said.
Teamed with his son, Ron Levin of MIT Lincoln Laboratory in Lexington, Massachusetts, the former Viking scientist said their belief is that Earth has infected Mars. All links in the vital chain connecting Mars and Earth can be clearly identified.
The bottom line: Earth and Mars were hospitable over epochs that would have permitted infection of Mars by Earth microorganisms, and from other sources. "Biology offers the only fit to the Label Release data from Mars and is consistent with our new knowledge about Mars and Earth. It is time to accept the LR results," he said.
Yet even Levin admits, additional proof is required before many scientists will accept such a major change in paradigm.
To this end, Levin is busy working on a miniaturized version of the original LR experiment. Hoping to find it a home on a future Mars lander, he said that the modified experiment can distinguish between chemical and biological reactions.
I got rhythm!
Another find in the two decades-plus Viking treasure-trove of data was outlined by Joe Miller, associate professor in the Department of Cell and Neurobiology at the Keck School of Medicine of the University of Southern California in Los Angeles.
Miller has recently reviewed the Viking LR data in great detail.
"To my surprise, in their LR experiment, they seemed to have clear periodic oscillations in the release of gas from a Martian soil sample injected with a nutrient solution. The oscillations in gas release had a period of what appeared to be one Martian day. Being a circadian biologist, I became very excited," Miller told SPACE.com.
On Earth, Miller said, circadian rhythms -- oscillations with a period of nearly 24 hours -- are present in every species examined down to blue-green algae. Was it possible, he asked, that the LR experiment was recording the circadian rhythm of a Martian soil-dwelling microbe?
NASA worked with Miller, providing him the 1976 LR data sets, as well as converting the information to an electronic format. That allowed the circadian biologist to study the data using modern computer-based analytical tools.
"I found that the gas release was indeed rhythmic, with a period of precisely 24.66 hours, a Martian day," Miller said. This finding, along with other painstaking assessments about LR operations, the scientist feels that a Martian circadian rhythm in the experiment may constitute a biosignature - a sign of life.
"In conjunction with a great deal of other data from this experiment, such as the very large increase in gas immediately following nutrient injection, as well as a slow rise over the course of the entire experiment, suggest that the LR experiment was seeing biology," Miller said.
Miller said, however, that chemical interpretations of some of these data are possible, perhaps accounting for part of the LR rhythm.
"On the whole, a biological explanation seems more plausible. In all probability, Viking discovered life on Mars 25 years ago. The presence of a strong circadian rhythm in the LR experiment further suggests that circadian rhythmicity may be an excellent 'biosignature' of extraterrestrial life," Miller said.
Fact of life
In a sense, there's a bit of an undeclared race to prove that organisms on Mars are a fact of life.
For one, the spunky British-built Beagle 2 is set to land on Isidis Planita, a large flat region that overlies the boundary between ancient highlands and the northern plains. Beagle 2 is to be deployed from ESA's Mars Express spacecraft that is slated to begin orbiting the planet in late 2003.
"If the Beagle 2 successfully lands in 2003 and if its GCMS discovers organic molecules at the surface, then this will strengthen the case that the LR results were due to Martian biology," Warmflash of NASA told SPACE.com.
Closing in on the red planet, NASA's Mars Odyssey is on schedule to swing itself into orbit around the planet this October. Then, twin rovers are being prepped to rumble over Martian terrain in 2004. While not geared for detecting Martian life, the wheeled craft will act as robotic field geologists, geared to discern what Mars was like a long time ago.
A super-slick and highly mobile rover is on NASA's books for a 2007 liftoff. Then, no earlier than 2011, the space agency is hoping to loft the first robotic return sample mission to Mars.
First-things-first
Michael Meyer, astrobiology discipline scientist at NASA Headquarters here, said that answering the life on Mars question boils down to acquiring more data.
"A majority of the scientific community tends to think that Levin didn't find evidence for life on Mars. The only way to resolve the issue is to go to Mars. It's better to do take a step-wise approach, instead of trying to second-guess instruments and rework data. The answer is to go back to Mars," Meyer said.
Meyer said that simple models about life have been turned on their head, thanks to more data gained since the 1970s. "In some ways, Viking was a little too Earth-centric. It presumed life has metabolism that we can recognize. It also presumed that if you land anywhere on Mars you can measure life," he said.
John Rummel, NASA's planetary protection officer, takes a first-things-first attitude. "Looking for life on Mars is understanding the planet well enough to know where to look for it in the first place," he said.
"Either it's pathetically obvious that there is life on Mars…or it's going to be very hard to find. Most bets are that it's very hard to find. Just getting to the place where you actually would find life is going to be difficult. A lot of what we're doing in the Mars program is to really understand Mars well enough to know where to look," he said.