NASA Curiosity rover on the Red Planet prowl since August 2012 and assessing the habitability of Mars.
Credit: NASA/JPL-Caltech/MSSS

Back in June, NASA held a press meeting to detail new findings from the space agency’s Curiosity Mars rover.

The Mars machinery had found new evidence preserved in rocks on Mars that suggests the planet could have supported ancient life, as well as new evidence in the Martian atmosphere that relates to the search for current life on the Red Planet. While not necessarily evidence of life itself, these findings are a good sign for future missions exploring the planet’s surface and subsurface.

“Are there signs of life on Mars?” said Michael Meyer, lead scientist for NASA’s Mars Exploration Program, at NASA Headquarters. “We don’t know, but these results tell us we are on the right track.”

History-making Viking Mars landers touched down on the Red Planet in 1976.
Credit: NASA

Critical review

A critique of that NASA announcement and related scientific papers has been written by former Viking experimenters. After landing in 1976, the two Viking craft carried out dedicated life-detection investigations.

Gilbert V. Levin was the leader of the Viking Labeled Release (LR) Life Detection Experiment and Patricia Ann Straat was a Viking co-experimenter.

Writing a Forum article in the journal Astrobiology, the two scientists note that the June 7, 2018, NASA news conference and two related papers in Science regarding the findings of organic molecules and methane on Mars “are exciting for the possibility of both ancient and current life on Mars.”

NASA’s Curiosity rover used an instrument called SAM (Sample Analysis at Mars) to detect seasonal changes in atmospheric methane in Gale Crater. The methane signal has been observed for nearly three Martian years (nearly six Earth years), peaking each summer.
Credit: NASA/JPL-Caltech


Indication of current life

That said, Levin and Straat write: “While ostensibly contending they are seeking life, each finding pointing in that direction seems to be immediately contra-indicated by the finders and in all of NASA’s releases and supported scientific publications.”

For instance, the paper on methane in the atmosphere of Mars did provide important new information, they add. That is, monitoring the localized seasonal cycling of atmospheric methane, with substantial and repetitive amplitudes over the three Martian years (six Earth years).

But while acknowledging that almost all methane in Earth’s atmosphere is of biological origin, the authors of that paper propose an abiotic scenario “to explain away this strong indication of current life,” Levin and Straat point out. “On the other hand, this new result makes a possible biological source proposed to explain the cyclical methane on Mars even more tantalizing,” the Viking scientists add.

Strong evidence

NASA has not dispatched another life-detection experiment to Mars since the 1976 Viking mission Labeled Release (LR) experiment, Levin and Straat write, despite that experiment obtaining “strong evidence” for current microbial life on the Red Planet.

Credit: NASA/Ben Clark

“At that time, this evidence was overridden by the presumed lack of liquid water and the failure of the Viking GCMS [Gas Chromatograph Mass Spectrometer] to find any organic matter. Both have now been found,” Levin and Straat point out.

“In the 41 years since Viking, none of the many attempts to explain away the LR results nonbiologically has withstood scientific scrutiny, so no barrier remains to preclude the possibility of extant microbial life on Mars, or that the LR experiment detected it,” Levin and Straat conclude.

Go to this NASA June 7, 2018 release regarding Curiosity’s findings at:

“Comments on the June 7, 2018, NASA News Release and Papers” by Gilbert V. Levin and Patricia Ann Straat has been published online: July 16, 2018 in Astrobiology at:

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