But Schulze-Makuch believes most of the experiments may have produced skewed results because they used too much water. (The labeled release, pyrolytic release and gas exchange experiments all involved adding water to the soil.)

"Since Earth is a water planet, it seemed reasonable that adding water might coax life to show itself in the extremely dry Martian environment," Schulze-Makuch wrote. "In hindsight, it is possible that approach was too much of a good thing." In very dry Earth environments, such as the Atacama Desert in Chile, there are extreme microbes that can thrive by hiding in hygroscopic rocks, which are extremely salty and draw in tiny amounts of water from the air surrounding them. These rocks are present on Mars, which does have some level of humidity that could hypothetically sustain such microbes. [...]

But too much water can be deadly to these tiny organisms. In a 2018 study published in the journal Scientific Reports, researchers found that extreme floods in the Atacama Desert had killed up to 85% of indigenous microbes that could not adapt to wetter conditions.

Therefore, adding water to any potential microbes in the Viking soil samples may have been equivalent to stranding humans in the middle of an ocean: Both need water to survive, but in the wrong concentrations, it can be deadly to them, Schulze-Makuch wrote.

It was also discussed on Lemmy. Wish we could link to posts.