In all our explorations of Mars to date, we have found no evidence that meets the stringent standards that would allow us to say with certainty that we have found life. But we may have come close to that decades ago, in the 1970s, when Viking became the first American mission to safely land on and explore the Red Planet.

A researcher has suggested that life exists in a sample of Martian soil. Then we destroyed it while trying to find it. It’s that simple. An experiment to detect signs of microbial life on Mars could have been fatal, according to astrobiologist Dirk Schulze-Makuh of the Technical University of Berlin in Germany.

Our methods can be destructive in their own right, he argues in a column published on the Big Think website last year and in a commentary published in the journal Nature Astronomy in September. If this is the case, we need to consider the Martian ecology carefully when planning future experiments. And Schulze-Makuch advises that with these thoughts in mind, humanity should send another mission devoted primarily to the search for life.

The two Viking rovers who landed on Mars in 1976 had a list of tasks ahead of them. One of them was conducting a series of experiments designed to test for the presence of biosignatures, traces of molecules in Martian soil that indicate the presence of life. These are the only targeted biological experiments conducted on Mars to date.

In one such experiment, a gas chromatography-mass spectrometer (GCMS) detected chlorinated organics. At the time, this result was interpreted as contamination from human detergents and thus zero detection of biological organisms. We now know that chlorinated organics are native to Mars, but it is unknown whether they were produced by biological or non-biological processes.

In recent years, there has been speculation about the harmfulness of Viking’s biological experiments. The HCMS needed to heat the samples to separate the various materials contained in the samples. Further analysis showed that this might have burned the organic matter he expected to find.

Schulze-Makuh now suggests that other experiments, such as labeled release and pyrolytic release experiments, which involved soaking Martian samples with liquid and then checking the results for signs of metabolism and photosynthesis, respectively, may have also destroyed the evidence.

The results indicated a positive signal, contrasting with the null results of the fourth experiment, gas exchange. Schultze-Makuh writes that it was and still is unclear.

But looking back, the release experiments were probably poorly designed. At the time, we assumed that life on Mars would be similar to life on Earth and would thrive in the presence of water, the more the better. But as we have recently learned, life can optimize itself to thrive in very dry conditions. And Mars is very dry. Change these conditions and prosperity may end.

“Now let’s ask, what happens if you pour water on these dry-adapted microbes? Can he destroy them? Technically speaking, we could say we’re over-watering them, but to the layman it’s more like drowning them,” Schulze-Makuh explains in his column.

It’s like a spaceship finding you half-dead in the desert and your would-be rescuers deciding: “People need water. Let’s put him in the middle of the ocean to save a person! That won’t work either.”

Interestingly, he notes that the signs of life found in the pyrolytic release experiment were much stronger in the dry control experiment, where no water was added to the sample. So it’s natural to wonder, as others have: Did these experiments find signs of life that we’ve been ignoring?

These signs are, of course, still controversial and far from conclusive. However, these may serve as the basis for further research.

In 2007, Schulze-Makuch suggested that dryness-adapted life might exist on Mars using hydrogen peroxide. He and co-author Jupp Houtkooper argue that the Viking results are not inconsistent with this hypothesis.

“If these findings about organisms surviving in extremely arid Martian conditions are correct, then we should additionally look for hydrated and hygroscopic compounds (salts) rather than ‘chasing water,’ which has long been NASA’s strategy in the search for life on the Red Planet — a key to finding microbial life.” as a way,” Schulze-Makuh concludes.

“Nearly 50 years after the Viking biological experiments, it is time for a new life-detection mission; we now have a much better understanding of the Martian environment.”

Comment posted on: Nature Astronomy.