While the ongoing quest to detect life on Mars continues, NASA's plan to retrieve samples from the planet is set to conclude in the early next decade. However, one scientist proposes an intriguing notion: that we potentially encountered life on the Red Planet nearly five decades ago, an encounter that may have ended tragically.
Before the Curiosity rover's historic journey, two preceding landers played a vital role. NASA's Viking program, launched in 1975, not only offered the first glimpses of Mars' landscape but also performed biological analyses of its soil, with the primary aim of unearthing indications of life.
A paradigm shift
The data from these probes prompted a paradigm shift among Earth's scientific community regarding the presence of water on Mars. The explorations unveiled numerous geological formations consistent with the effects of substantial water flows. Vast river channels were revealed in various regions, and evidence emerged of catastrophic water surges that breached dams, carved extensive valleys, gouged rock formations, and traversed thousands of kilometers. Extensive networks of branching channels and streams were prevalent across the southern hemisphere, underscoring the likelihood of past rainfall on Mars. Scientists even found that the slopes of Martian volcanoes were similar to the ones in Hawaii, which would mean they were exposed to rain. Certain craters even displayed characteristics akin to impacts on muddy terrain.
The experiments
Nevertheless, a series of experiments yielded perplexing outcomes that confounded scientists. The landers conducted three distinct experiments. The first produced affirmative results hinting at metabolic processes. However, the adverse effects of the subsequent two experiments, which failed to detect organic substances, led researchers to speculate that the initial positive result might have been due to non-biological chemical reactions. In simpler terms, the first experiment detected traces of organic materials combined with chlorine, likely contaminants inadvertently transported from Earth.
Another aspect of the experiment involved introducing water infused with nutrients and radioactive carbon (carbon-14) to the Martian soil. The hypothesis was that the radioactive carbon would have been released as a gas by Martian microorganisms, who would consume the nutrients. Although the initial experiment indicated this radioactive gas's emission (absent in a control experiment), the remaining results remained inconclusive. According to an explanation on the scientific platform "iflscience," the presence of bacteria should have resulted in increased gas production with additional nutrient injections and prolonged incubation. However, successive injections failed to trigger more gas emissions. The likely culprit for the initial positive reading was perchlorate, a compound utilized in rocket fuel, which could have altered nutrient processing.
The other theory
Yet, an alternative theory exists. Prof. Dirk Schulz-McKoch, an authority on planetary habitation and astrobiology at the Technical University of Berlin, posits that including water in the experiment might have been an oversight, potentially leading to the demise of the very bacteria being sought.
In a June publication in BigThink magazine, he cites Earth-based life thriving in extreme environments, such as bacteria within salt rocks that draw moisture from the air. Submerging these bacteria in water could prove fatal, potentially explaining the absence of radioactive gas detection despite additional nutrient injections. Prof. Schultz-McKoch had previously proposed the possibility of Martian life containing hydrogen peroxide within their cells. In a 2007 study, he outlined the advantages of such a configuration for Martian life, including a low freezing point, a source of oxygen, and hygroscopicity.
He wrote, "If we assume that indigenous Martian life might have adapted to its environment by incorporating hydrogen peroxide into its cells, this could explain the Viking results." He added, amusingly, that the gas chromatograph mass spectrometer subjected samples to heating before analysis. "If the Martian cells contained hydrogen peroxide, that would have killed them. Moreover, it would have caused the hydrogen peroxide to react with any organic molecules in the vicinity to form large amounts of carbon dioxide—which is exactly what the instrument detected.."
Although speculative, this notion posits that humanity possibly encountered life on Mars nearly five decades ago, inadvertently terminating it shortly after the discovery.