There's something quite curious about Curiosity, according to one Mars researcher.

A scientist who worked on NASA's 1976 Viking landers to the Red Planet claims that the Mars Science Laboratory's Curiosity rover carries gear he labels as "stealth life detectors."

Curiosity is due to land on Mars tonight (Aug. 5) at 10:31 p.m. PDT (1:31 a.m. EDT and 0531 GMT on Aug. 6). The $2.5 billion rover is slated for a two-year mission to search for signs that the planet is or was habitable to life. Mission managers have stopped short of claiming the probe is looking for life itself, however.

Gilbert Levin was a life-detection experimenter on NASA's Viking mission to Mars and is now an adjunct professor at Arizona State University in Tempe. With Levin as experimenter and Patricia Ann Straat as co-experimenter, the Viking Labeled Release (LR) investigation returned data from Mars indicating the presence of microbial life, the team asserts. [The Life on Mars Search: Photo Timeline]

Levin contends that the organic analyzers and the high-resolution camera on Curiosity may bring about a re-evaluation of the Viking LR findings, "which, I believe, would support my claim," he said.

Declaration of finding life

Some 36 years ago on Mars, Viking's LR experiment injected a tiny drop of radioactive nutrients on a thimble-full of Martian soil and then looked for the rising of radioactive gas as evidence of metabolism.

To ensure that the gas had not come from a chemical reaction, a second sample of the soil was heated at a temperature to kill microorganisms, but not high enough to destroy possible chemical reactants. This "control" sample was then tested in the LR.

Levin said that on Mars, the untreated soils gave positive results, and the heat-treated control samples were negative, indicating that the positive reactions were biological. A total of nine experiments at both Viking landing sites, some 4,000 miles apart, supported the positive responses as being biological. However, because another Viking instrument failed to find organic matter, the stuff of life, NASA concluded the LR results were ambiguous at best.

Over the years, Levin's declaration of finding life has been gauged as controversial.

Virtual experiment

Fast forward to the upcoming attempt to plop the Curiosity rover safely down on Mars.

"I am very closely watching Curiosity, inasmuch as I have claimed it as my own," Levin told SPACE.com, "since NASA abandoned it by so vigorously stating it is not looking for life."

Levin intends to purloin MSL's results for his own purposes. "I feel certain that my appropriated MSL will confirm that the Viking LR experiment did, indeed, detect life on the surface of Mars in 1976."

If no organics or visible confirmation of life are found by the sensitive MSL instruments, "that will be a miracle harder to explain than if life on Mars is confirmed," Levin said.

Curiosity's Sample Analysis at Mars (SAM) Suite Investigation is designed to address the present and past habitability of Mars by exploring molecular and elemental chemistry relevant to life. SAM addresses, among other duties, carbon chemistry through a search for organic compounds.

NASA's unexplained intention

Levin's said that another "virtual experiment" of his aboard Curiosity is its microscopic imager. That instrument has sufficient resolution to see individual grains of silt.

Curiosity's Mars Hand Lens Imager (MAHLI)consists of a camera mounted to a robotic arm on the rover, used to acquire microscopic images of rock and soil.

Levin thinks this camera can determine whether "lichen-like" colored patches might exist on Martian rocks. That claim stems from his review of all 10,000 Viking lander images, in which he found on some rocks possible evidence of living organisms.

Curiosity may inadvertently produce acceptance of the Viking LR investigators' claim to have detected life, Levin said, "thereby negating NASA's unexplained intention to indefinitely defer knowledge about life on Earth's nearest neighbor."

Levin thinks that Curiosity's results, coupled with the Viking LR findings, can bring about a realization that we are not alone in the universe.

To that effect, Levin said, should Curiosity detect organic matter, the last obstacle to general acceptance of his claim to have discovered life on Mars will vanish.

Finding a sweeter spot

Taking issue with Levin is John Rummel, chairman of the Committee on Space Research (COSPAR) Panel on Planetary Protection. He's a former NASA planetary protection officer, as well as former exobiology program manager and senior scientist for astrobiology at NASA Headquarters.

"Until we find a sweeter spot on Mars than we can currently land on, active life detection instruments are not very useful. We will get there, I am sure," Rummel told SPACE.com

Rummel said that, at best, Curiosity can replicate certain LR parameters, and may be able to understand them by multiple experiments. "But the presence of organics will still bedeterminative with respect to the acceptance life," he added.

SAM may be able to detect extremely low levels of organics, Rummel noted, and if so then the potential for life and/or habitability will be established — but not the actual LR experimental results, which are not subject to replication, overall, he said.

Interpretation of LR results

"It is simply incorrect that NASA has had an explicit 'ban' on life detection experiments," Rummel said. "That has never been the case, and likely never will be."

Levin will be watching to see if his original LR results are "confirmed." However, Rummel said the Viking results aren't in need of substantiation, per se.

"They only need to be placed into the broader context of the real surface of Mars, which will be unlikely to allow the interpretation of the LR results as an unequivocal detection of life in 1976," Rummel said. "We don't need a 'do-over'…rather a 'do-more' to tell us about Mars life."

Visit SPACE.com for complete coverage of NASA's Mars rover landing.

Leonard David has been reporting on the space industry for more than five decades. He is a winner of last year's National Space Club Press Award and a past editor-in-chief of the National Space Society's Ad Astra and Space World magazines. He has written for SPACE.com since 1999.