ES News email The latest headlines in your inbox twice a day Monday - Friday plus breaking news updates Enter your email address Continue Please enter an email address Email address is invalid Fill out this field Email address is invalid You already have an account. Please log in Register with your social account or click here to log in I would like to receive lunchtime headlines Monday - Friday plus breaking news alerts, by email Update newsletter preferences

A former Nasa scientist claims evidence of life was found on Mars in the 1970s but was ignored.

Viking landers, a pair of space probes, were sent to the Martian surface more than 40 years ago to explore the planet.

One of the tests they ran was known as Labeled Release, or LR, which was intended to look for signs of life.

Back in the lab, the results seemed to indicate something was happening on the surface.

The principal investigator on the experiment, Gilbert V Levin, has now written an article arguing those findings were indications of alien life on Mars. Signs, he says, were ignored by Nasa.

It was back as far as July 30, 1976, when the team Levin was heading up got the initial results from the LR. "Amazingly, they were positive," he writes in the Scientific American.

"As the experiment progressed, a total of four positive results, supported by five varied controls, streamed down from the twin Viking spacecraft landed some 4,000 miles apart.

"The data curves signaled the detection of microbial respiration on the Red Planet. The curves from Mars were similar to those produced by LR tests of soils on Earth.

"It seemed we had answered that ultimate question."

Ultimately, Nasa's tests failed to find organic matter, the physical stuff of life itself. It determined the indications of microbial respiration that the LR experiment discovered came from a substance mimicking life, but was not life itself.

Since then, Nasa has not run a similar experiment choosing to focus on whether Martian habitat could be a suitable home for alien life.

But Levin argued what he and his team found almost half a century ago actually suggested there is life on Mars. Levin believed Nasa should be doing more to follow the findings up because they could pose a significant threat to life on Earth.

"NASA maintains the search for alien life among its highest priorities," he wrote. On February 13, 2019, NASA Administrator Jim Bridenstine said we might find microbial life on Mars.

"Our nation has now committed to sending astronauts to Mars. Any life there might threaten them, and us upon their return. Thus, the issue of life on Mars is now front and center."

The evidence Levin said he found produced a whole host of positive results and importantly, no experiment has disproved what he found or found an alternative explanation for the results.

He concluded by asking Nasa to carry out an altered version of the LR on Mars on the next possible trip and asked that scientists be brought together to examine the decades-old findings to see if they really are proof of life on Mars.

"What is the evidence against the possibility of life on Mars? The astonishing fact is that there is none," he wrote. "Furthermore, laboratory studies have shown that some terrestrial microorganisms could survive and grow on Mars," Levin said.

"Such an objective jury might conclude, as I did, that the Viking LR did find life," he wrote. "In any event, the study would likely produce important guidance for NASA’s pursuit of its holy grail."