Characterization of Organics, Microorganisms, Desert Soils, and Mars-like Soils by Thermal Volatilization Coupled to Mass Spectrometry and Their Implications for the Search for Organics on Mars by Phoenix and Future Space Missions

Abstract A key goal for astrobiology is the search for evidence of life on Mars. Because liquid water is a fundamental environmental requirement for life, the recent set of missions to Mars have focused on a strategy known as “follow the water.” Since life is made of organic molecules, a logical next step is “follow the organics.” However, organics are expected to be present at very low levels on Mars, which would make their detection challenging. Viking was unable to detect organics at parts per billion (ppb), but the effective upper limit could be higher due to the low efficiency of the thermal volatilization (TV) step in releasing organics. Due to its ease of use, TV is still the method selected for current and future NASA and ESA missions. Here, we show that when organics are present in the soil at levels above 1500 parts per million (ppm), there are several characteristic organic fragments detected by TV–mass spectrometry; however, when the levels are below <150 ppm, TV oxidizes them, and no organic ...