Earth’s atmosphere provides a thin barrier to the severe conditions of space. Globally, terrestrial microorganisms from our planet’s surface move through and interact with the blanketing atmosphere, analogous to how marine microbes drift through vast oceans. Whereas a century of exploration has allowed oceanographers to characterize marine life at nearly every depth, the same is not true for the “ocean” of air above our heads. High‐altitude exploration has been severely constrained by a shortage of reliable experimental systems. This seminar will discuss recent advances in the microbiological exploration of Earth’s atmosphere with the use of high-flying NASA aircraft and large scientific balloons launched from the USA and Antarctica. Discoveries from these platforms can provide biophysical insights for the field of astrobiology and inform the search for life beyond this planet. Specifically, our results indicate: (1) Earth’s stratosphere is a natural laboratory for assessing the potential survivability of microbes on the surface of Mars which possesses a similar combination of conditions (high radiation levels and ultralow temperature, pressure, and relative humidity); and (2) Methods for reliably collecting and detecting trace levels of microbial biomass at extreme altitudes can contribute to life detection strategies for other solar system targets.

David J. Smith is a NASA microbiologist who founded the Aerobiology Laboratory at Ames Research Center prior to joining the Planetary Science Division at NASA Headquarters in October 2022.