The Cosmic Ray Exposure Sequencing Science (CRESS) payload system is 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 high-latitude and long-duration balloon flight carrying the Boron And Carbon Cosmic Rays in the Upper Stratosphere (BACCUS) experimental hardware. Investigation of the biological effects of Galactic Cosmic Radiation (GCR) particularly those of ions with High-Z and Energy (HZE) is of interest due to the genomic damage this type of radiation inflicts. The biological effects of upper-stratospheric mixed radiation above Antarctica (ANT) were sampled using Arabidopsis thaliana seeds and were compared to those resulting from a controlled simulation of GCR at Brookhaven National Laboratory (BNL) and to laboratory control seed. The payload developed for Antarctica exposure was broadly designed to 1U CubeSat specifications (10cmx10cmx10cm <1.33kg) maintained 1 atm internal pressure and carried an internal cargo of four seed trays (about 580,000 seeds) and twelve CR-39 Solid-State Nuclear Track Detectors (SSNTDs). The irradiated seeds were recovered sterilized and grown on Petri plates for phenotypic screening. 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 significantly higher than that of ANT. Genomic DNA from mutants of interest was evaluated with whole-genome sequencing using PacBio SMRT technology. Sequence data revealed the presence of an array of genome structural variants in the genomes of M0 and M1 mutant plants.