NASA’s twin Viking spacecraft may have missed signs of life during their examination of the Martian surface 30 years ago. Researchers now say that the landers‘ experiments were not sensitive enough to find life and in any case may not have been able to spot the strange forms that Martian life might take. The results from Vikings‘ onboard experiments are confusing because some tests suggested the presence of organisms capable of digesting organic molecules. But heating the soil with a gas-chromatograph mass spectrometer to release these organic molecules found nothing, causing most scientists to rule out life. Now, a paper by Rafael Navarro-Gonzalez of the University of Mexico and others demonstrates that the mass spectrometer onboard Viking was incapable of detecting organic compounds even in Mars-like soils from various locations on Earth. This includes Chile’s Atacama desert, where other tests prove that living microbes are indeed present, and samples taken from Rio Tinto in Spain, which contain iron compounds similar to those detected in Mars soils by the Mars Exploration Rover „Opportunity“.

The limitations on organic detection in Mars-like soils by thermal volatilization–gas chromatography–MS and their implications for the Viking results