According to astrobiologist Dirk Schulze-Makuch of the Technical University Berlin in Germany, an experiment to detect the signs of microbial life on Mars could have been deadly.
But the release experiments were likely poorly conceived, in retrospect.
At the time, we assumed that life on Mars would be like life on Earth and thrive in the presence of water – the more the merrier.
So it seems natural to wonder, as others have: did these experiments detect signs of life that we dismissed?
The Viking results, he and his co-author Joop Houtkooper assert, are not incompatible with this hypothesis.
No proof that we have definitively discovered life on Mars has been discovered in all of our previous explorations.
However, we might have been close decades ago in the 1970s, when the Viking landers were the first US mission to safely land on and explore the red planet.
In a sample of Martian soil, one researcher suggests that life might have existed. We then extinguished it while attempting to sniff it. In that exact same vein.
An attempt to find evidence of microbial life on Mars might have been fatal, according to astrobiologist Dirk Schulze-Makuch of the Technical University Berlin in Germany.
In a September commentary in Nature Astronomy and a column on Big Think last year, he speculates that our own techniques might have been harmful in and of themselves.
If this is true, we must carefully take Mars’ ecology into account when planning our next experiments. In light of these factors, Schulze-Makuch suggests that humanity send another mission that is primarily focused on the search for life.
In 1976, the two Viking landers had a set of goals when they touched down on Mars. One of those was to carry out a series of tests intended to look for biosignatures, or traces of molecules that suggest the existence of life, in the Martian soil.
These are the only biological experiments conducted specifically on Mars to date.
The gas chromatograph-mass spectrometer (GCMS), one of those experiments, discovered chlorinated organics. When that result was obtained, it was thought to be a null detection for biological signs due to contamination from human cleaning products.
It is now known that chlorinated organics are indigenous to Mars, but it is still unclear if biological or non-biological processes create them.
The destructiveness of the Viking biological experiments has been the subject of some conjecture in recent years. To extract the different materials from the samples, the GCMS had to heat them. That might have burned the very organics it was looking for, according to further analysis.
Now, Schulze-Makuch argues that other experiments, such as the pyrolytic release and labeled release experiments, which involved injecting liquid into Martian samples and then examining the results for signs of photosynthesis and metabolism, respectively, may have also destroyed evidence.
The results indicated a positive signal, which appeared to be in conflict with the gas exchange, the fourth experiment’s null results. “This was and is confusing,” writes Schulze-Makuch.
In hindsight, however, the release experiments were probably ill-conceived. Back then, we thought that life on Mars would be similar to life on Earth and would flourish in water, the more the better.
However, as we have discovered more recently, life can adapt to survive in extremely dry environments. Additionally, Mars is extremely dry.
If those circumstances change, the thriving might very well come to an end.
Here’s a question: what would happen if these dry-adapted microbes were covered with water? Could that overwhelm them? “In technical terms, we would say that we were hyperhydrating them, but in plain English, it would be more like drowning them,” Schulze-Makuch wrote in his column.
“If an extraterrestrial spacecraft discovered you half-dead in the desert, your would-be rescuers would conclude that “humans need water.”. That wouldn’t work either. Let’s put the human in the middle of the ocean to save it. “,”.
Curiously, he notes, the dry control run, which did not add water to the sample, had significantly stronger life signs than the pyrolytic release experiment. Therefore, it would seem reasonable to ask, as others have, if these experiments found life that we had previously rejected.
To be clear, those indications are still incongruous and far from definitive. However, they might merit more research.
In 2007, Schulze-Makuch postulated that dry-adapted life that uses hydrogen peroxide might exist on Mars. He and his co-author, Joop Houtkooper, claim that the Viking results do not contradict this theory.
“We should also follow hydrated and hygroscopic compounds – salts – as a way to locate microbial life,” Schulze-Makuch concludes, “if these inferences about organisms surviving in hyperarid Martian conditions are correct, then instead of ‘follow the water,’ which has long been NASA’s strategy in searching for life on the red planet.”.
“Now that we have a far better understanding of the Martian environment, it is time for another life detection mission, nearly 50 years after the Viking biology experiments. “..”.
Nature Astronomy publishes the commentary.
Prior to the recent Nature commentary, this article was published in August 2023.
