Life found on Mars! Surely it would be the story of the century except perhaps it was the story of last century and everybody missed it. That’s the extraordinary claim of Gilbert Levin, the principal investigator of a NASA experiment that went to Mars in 1976 with the Viking landers.


The Labelled Release (LR) experiment placed liquid nutrients onto Mars soil samples. The idea was that any microorganisms present would consume the food and give off carbon dioxide gas.

“We were astonished to find that we immediately got gas coming out and it continued for the full seven days of the experiment,” says Levin.

At first, even Levin himself was sceptical to believe that his experiment had found life, and thought that the ultraviolet light penetrating to the surface of Mars was affecting the chemistry of the soil, and priming it to release the carbon dioxide. So he got the spacecraft engineers to move a rock and take a sample of soil from underneath. His results remained the same.

Next, it was suggested that hydrogen peroxide in the atmosphere and surface of Mars was responsible. But Levin investigated the data taken by Mariner 9, a previous Mars spacecraft, and found no trace of the chemical.

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“Over the 43 years there have been at least 40 theories and experiments to explain away the LR life detection results,” says Levin, who contends that none of these explanations stand up to scientific scrutiny.

Consequently, Levin now believes that his experiment did find life on Mars. NASA, however, points to other experiments on Viking that failed to find any sign of organic molecules in the soil samples. Without organic molecules, life would be impossible.

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Levin suggests that the way out of the stalemate is to fly a new LR experiment to Mars, and has even updated the design to identify a telltale characteristic of life’s chemistry called ‘chirality’.

Wild ideas in science: We've already found life on Mars © Scott Ballmer
© Scott Ballmer

But as yet, no space agency seems to want to fly the experiment. Instead, Levin is part of an experiment called HABIT, which is going to Mars onboard ESA’s Rosalind Franklin rover, which is scheduled for launch in summer 2020.

The HABIT experiment will look for evidence that small puddles of water form on the Martian surface at dawn. Other experiments on the rover will look for chemicals that could indicate the presence of past or present life.

Positive results from such experiments may change the space agencies’ minds about sending a new version of Levin’s LR experiment, which looks for active metabolisms.


There can be no doubt that the scientific and public interest in looking for life on Mars is high. How ironic it would be if we find out that we already detected it more than 40 years ago.

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Dr Stuart Clark is an astronomer, science journalist and author of several popular science books, the latest of which is Beneath the night: How the stars have shaped the history of humankind. You can find a version of his book, remade for radio, called Beneath the Night over on BBC sounds. Stuart is also a fellow of the Royal Astronomical Society and he regularly works with European Space Agency to communicate their work to the general public.