No place on Earth has the exact conditions we see on Mars. Scientists believe the Red Planet once had rivers with flowing water. Today, though, the planet’s surface is an arid wasteland with an atmosphere 100 times thinner than ours.
Still, some regions of Earth can serve as an approximate representation of Mars’ extreme environment. Perhaps the closest analog to Mars on Earth is the Atacama Desert in Chile. It is the driest nonpolar desert on Earth, and it experiences almost no rain.
One scientist, Dr. Dirk Schulze-Makuch, a professor of planetary habitability and astrobiology at the Technical University Berlin, has studied microbial life in the desert for years. He believes what he has learned could have massive implications in the search for alien life.
In fact, Schulze-Makuch believes NASA may have already detected life on Mars with its Viking landers in the 1970s. As microbial life in the Atacama Desert dies when exposed to too much water, the space agency may have killed this life with its liquid water life detection experiments. In other words, in trying to find life on Mars, NASA may have obliterated it instead.
Not all hope is lost, however. According to Schulze-Makuch, this hypothesis points to a new avenue of investigation: “NASA should look for landing sites with hygroscopic salts, as these allow microbes to attain water in extreme deserts,” he told Interesting Engineering in an interview.
Searching for signs of Martian life
All life on Earth requires water to survive. And yet, over millions of years, microbial life in the hyperarid region of the Atacama Desert has adapted to life with almost no water. They live in salt crusts and undergo prolonged periods of dormancy. To survive, they rely largely on hygroscopic salts, which attract and absorb water from the surrounding atmosphere. This gives the microbes access to relatively concentrated amounts of water in an otherwise dry landscape.
The incredible adaptability of these microbes – also known as extremophiles – shows the resilience of life on Earth. It also poses important questions about the search for alien life on Mars.
To date, NASA has focused its investigations on ancient waterways on Mars. The Perseverance rover, for example, touched down on the ancient Jezero lakebed, in 2021. Since that time, it has been collecting samples of Martian soil and leaving them for future missions to return to Earth. The space agency, and the global scientific community, hopes those samples will contain signs of ancient microbial life.
According to Schulze-Makuch, however, we should be focusing on salts rather than water. On such an arid planet surface, microbes are more likely to exhibit the behavior they do in the Atacama Desert.
The Technical University Berlin professor, who has also served as a faculty fellow at the NASA Goddard Space Flight Center, said his research into the Atacama Desert guided his recent work. It helped him “understand how microbes survive in the most extreme desert where it hardly ever rains and how these organisms can survive even without any precipitation – which you wouldn’t have on Mars either.”
In an article published in the journal Nature Astronomy, titled “We may be looking for Martian life in the wrong place,” Schulze-Makuch highlights his belief that NASA should re-focus its search on salt-rich regions of Mars. He argues the space agency should hone in on regions rich in hygroscopic salts, such as table salt (NaCl), KCL, chlorates, and also perchlorates. In his article, he highlights the Red Planet’s Southern Highlands as a potential landing site.
Impressively, Schulze-Makuch also goes a step further than suggesting a new avenue of research for NASA. He believes we should reassess old findings made by the space agency’s Viking landers. Based on what we know today, the landers may have already discovered microbial alien life in the 70s.
NASA’s Viking program sent two identical probes, Viking 1 and Viking 2, to Mars. Both of these consisted of an orbiter to take photographs of the planet, and a lander to conduct experiments on its surface. The orbiters also served as communication relays to send data from those experiments back to Earth.
Once they reached their destination in 1976, the two landers began their extensive investigations. One day, they reported a potential positive detection of microbial life in one of their soil samples. Today, most scientists believe those readings were false positives, possibly caused by organics that attached to the landers during assembly on Earth. In the best-case scenario, they would say the results are inconclusive.
According to Schulze-Makuch, these readings may have another explanation that could be explained by research into microbial life in the Atacama Desert.
“When one region in the Atacama was flooded, it killed about 80 percent of the bacteria which were adapted to extreme dryness conditions,” he told IE, as shown in a 2018 study. And it wouldn’t take so much water to kill cells within a single soil sample. In fact, according to Schulze-Makuch “too much application of water during [Viking’s] life detection experiments would have drowned Martian life adapted to extreme dryness.”
NASA’s Viking experiments were conducted under the assumption that life requires liquid water to survive. However, the scientific community didn’t have the same insight into extremophiles that it does today.
During the Viking missions, the global scientific community also had less knowledge of the Martian environment. The Viking life detection experiments were largely inspired by culturing techniques used to identify microbes in scientific laboratories on Earth. Typically, this would involve adding water to samples to search for signs of microbial life.
According to Schulze-Makuch, the scientific community should re-assess all three of Viking’s biology experiments: the Gas Exchange Experiment (GEX), the Labeled Release (LR), and the Pyrolytic Release (PR).
“The gas exchange experiment [in particular] I still can’t really make much sense of [and] it and would need re-evaluation,” Schulze-Makuch explained. “But really, all experiments should be re-evaluated, since we now have – 50 years later – a much better understanding of Martian environments.”
Schulze-Makuch views are undoubtedly controversial as they go against the scientific consensus regarding the Viking experiments. Still, the scientist claims he has received encouragement from his peers. “I haven’t faced much criticism at all,” he explained, “More like encouragement that we should test this hypothesis. Not that there is proof of life on Mars, but if there is life on Mars, then it could survive in this way.”
