A mystery surrounds NASA's Viking 1 spacecraft that entered Mars' orbit in 1975, eventually landing on the surface of the Red Planet and becoming the first American spacecraft to touch down on Mars.
One of Viking 1's goals was to test if life resided on the surface of Earth's neighbor, and at the time, much of the testing methodology mimicked processes used on Earth to test samples for the presence of microbes. These processes involve the use of water, one of life's main ingredients, but according to one scientist, the involvement of water could have been what killed any Martian life within the soil samples, resulting in the testing results being negative.
Dirk Schulze-Makuch, an astrobiologist at the Technische Universität Berlin in Germany recognizes the possibility that life may have been discovered by Viking, but the water-based testing process of its experiments could have unintentionally killed it.
According to commentary published in the journal Nature Astronomy, Dirk Schulze-Makuch suggests, "We may be looking for Martian life in the wrong place," and then drew comparisons between the barren wasteland that is the Martian landscape and some of the driest places on Earth. The scientist suggests that microbes on Earth within the driest places on Earth retain their water through salts, which draw moisture from the atmosphere.
These salts are extremely sensitive to water, which means when Viking combined its soil samples with water to test for life it could have unintentionally killed any traces of it, simply because its testing processes was incorrect. Dirk Schulze-Makuch suggests NASA include multiple life-testing processes for any Martian samples.