Balloon-based exposed payload designed for astrobiological research in Earth’s near space

Earth’s near space, located in the region between 20 and 100 km above sea level, is characterized by extreme conditions, such as low temperature, low atmospheric pressure, harsh radiation, and extreme dryness. These conditions are analogous to those found on the surface of Mars and in the atmosphere of Venus, making Earth’s near space a unique natural laboratory for astrobiological research. To address essential astrobiological questions, teams from the Chinese Academy of Sciences (CAS) have developed a scientific balloon platform, the CAS Balloon-Borne Astrobiology Platform (CAS-BAP), to study the effects of near space environmental conditions on the biology and survival strategies of representative organisms in this terrestrial analog. Here, we describe the versatile Biological Samples Exposure Payload (BIOSEP) loaded on the CAS-BAP with respect to its structure and function. The primary function of BIOSEP is to expose appropriate biological specimens to the harsh conditions of near space and subsequently return the exposed samples to laboratories for further analysis. Four successful flight missions in near space from 2019 to 2021 have demonstrated the high reliability and efficiency of the payload in communicating between hardware and software units, recording environmental data, exposing sample containers, protecting samples from external contamination, and recovering samples. Understanding the effects of Earth’s near space conditions on biological specimens will provide valuable insights into the survival strategies of organisms in extreme environments and the search for life beyond Earth. The development of BIOSEP and associated biological exposure experiments will enhance our understanding of the potential for life on Mars and the habitability of the atmospheric regions of other planets in the solar system and beyond.