Nasa found evidence of alien life in the 1970s, according to a former senior scientist – and ignored it.

The Viking landers were sent to the Martian surface more than 40 years ago, with the aim of exploring the planet. They included an experiment known as Labeled Release, or LR, which was intended to look for signs of life on the planet.

The results came back in 1976 – and seemed to indicate that something was happening on the surface. Gilbert V Levin – an engineer and inventor who was the principal investigator on the experiment – has now written a long article arguing that those findings were indications of life on Mars, which were ignored by Nasa.

“On July 30, 1976, the LR returned its initial results from Mars,” Levin wrote in an article for Scientific American. ”Amazingly, they were positive.

“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.

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“It seemed we had answered that ultimate question.”

But Nasa’s experiments failed to find organic matter: the physical stuff of life itself, not just the indications of microbial respiration that the LR experiment discovered. That meant that Nasa concluded that the LR results came from a substance that was mimicking life but was not actually life itself.

Since then, Nasa has not a run a similar experiment has focused on examining whether the Martian habitat could be a suitable home for alien life.

But Levin argues that those findings actually suggested that there is alien life on Mars. And, he argued, Nasa must do more to follow them 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.”

Summing up the evidence of alien life, he wrote his experiment had found a whole host of positive results. But perhaps most strongly of all, he said there had been no experiment that had provided an alternative explanation for the results that came back from the LV experiment.

“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.”

In his conclusion, he asked that Nasa conduct the same kind of experiments again, taking an altered version of the LR experiment to Mars on the next possible trip. And he asked that scientists be convened to examine those more than 40-year-old findings to see if they really were proof of life on Mars.