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The Cosmic Ray Exposure Sequencing Science (CRESS) payload system was a proof of concept experiment to assess the genomic impact of space radiation on seeds. CRESS was designed as a secondary payload for the December 2016 high-altitude, long-duration south polar balloon flight carrying the Boron and Carbon Cosmic Rays in the Upper Stratosphere (BACCUS) experiment. Investigation of the biological effects of Galactic Cosmic Radiation (GCR), particularly those of ions with High-Z and Energy (HZE), was of interest due to the genomic damage this type of radiation inflicts. The biological effects of radiation above Antarctica (ANT) were studied using Arabidopsis thaliana seeds and compared to a simulation of GCR at Brookhaven National Laboratory (BNL) and to laboratory control seeds. The CRESS payload was broadly designed to 1U CubeSat specifications (10 cm x 10 cm x 10 cm, =1.33 kg), maintained 1 atm internal pressure, and carried an internal cargo of 580,000 seeds and twelve CR-39 Solid-State Nuclear Track Detectors (SSNTDs). Exposed BNL and ANT M0 seeds showed significantly reduced germination rates and elevated somatic mutation rates when compared to non-irradiated controls, with the BNL mutation rate also being higher than that of ANT. Genomic DNA from plants presenting distinct aberrant phenotypes was evaluated with whole-genome sequencing using PacBio SMRT technology, which revealed an array of structural genome variants in the M0 and M1 plants. This study was the first whole-genome characterization of space-irradiated seeds and demonstrated both the efficiency and efficacy of Antarctic longduration balloons for the study of space radiation effects on eukaryote genomes. [ABSTRACT FROM AUTHOR]