➀ NASA's Viking 1 spacecraft, which landed on Mars in 1975, may have inadvertently killed potential Martian life during an experiment; ➁ Astrobiologist Dirk Schulze-Makuch suggests that the water-based testing methods used could have been too harsh for Martian microbes; ➂ Schulze-Makuch recommends that NASA use multiple life-testing processes for Martian samples.