The article discusses the Viking missions to Mars and the evidence suggesting the existence of life on the planet. The Viking landers conducted experiments designed to detect biological processes in Martian soil. Results from the labeled-release and gas-exchange experiments showed initial positive responses, indicative of microbial activity, but these declined rapidly, leading to skepticism.
The pyrolytic-release experiment, however, produced the strongest evidence. This experiment, designed to detect photosynthesis, yielded a positive response exceeding expectations, indicating organic molecule creation in the presence of sunlight. Despite this, the absence of organic molecules detected by the GCMS (gas-chromatograph mass-spectrometer) created a major controversy.
The article explores several theories to reconcile the positive biological results with the lack of detected organic molecules, including:
The article also considers the possibility of organic molecule destruction by ultraviolet radiation, but this theory is weakened by tests on soil shielded from UV radiation.
Despite the absence of large organic molecule accumulations, the article concludes that the collective evidence from Viking strongly suggests biological activity on Mars. It emphasizes that even the simplest findings have vast implications for understanding the prevalence of life in the universe and the potential for contact with extraterrestrial intelligence.