We may have already discovered the essence of life on Mars 40 years ago, according to a former NASA scientist.
The experiment, called Labeled Release (LR), was designed to test Martian soil for organic matter. "It seemed we had answered that ultimate question," Levin wrote in the article.
In the experiment, the Viking probes placed nutrients in Mars soil samples—if life were present, it would consume the food and leave gaseous traces of its metabolism, which radioactive monitors would then detect.
To make sure the test result was a biological reaction, the soil was cooked, and the test repeated. Cooking the soil would be lethal to known life. If there were a measurable reaction in the first and not the second sample, that would suggest biological forces at work—and that's precisely what happened, according to Levin.
"NASA concluded that the LR had found a substance mimicking life, but not life," said Levin in his article. "Inexplicably, over the 43 years since Viking, none of NASA's subsequent Mars landers has carried a life-detection instrument to follow up on these exciting results."
"What is the evidence against the possibility of life on Mars?" Levin wrote. "The astonishing fact is that there is none."
"NASA has already announced that its 2020 Mars lander will not contain a life-detection test," Levin wrote in the Scientific American article. "In keeping with well-established scientific protocol, I believe an effort should be made to put life detection experiments on the next Mars mission possible."
He proposed that the LR experiment be repeated on Mars, with certain amendments, and then have its data studied by a panel of experts.
"Such an objective jury might conclude, as I did, that the Viking LR did find life," he wrote.
The rover will look for past habitable environments, find biosignatures in rock, and will test those samples back on Earth.
