Chroococcidiopsis contains species from multiple extreme environments, providing the opportunity to study intrageneric adaptation. Due to its extremophilic nature, Chroococcidiopsis is a candidate for off-planet settlement and as a model for life elsewhere. Eight unialgal strains cultured from diverse habitats were characterized for their ability to survive a range of extreme environments. The study revealed two previously uncharacterized but phylogenetically-related saltwater isolates that were more radiation resistant than the others, CCMP 1991 from Hawaii and to a lesser extent, CCMP 3184 from Samoa. The Hawaiian isolate repaired thymine dimers in the light faster than the Samoan isolate, suggesting repair by photoreactivation. The Hawaiian isolate was more tolerant to H2O2 than the Samoan isolate, indicating a protective role for antioxidants. Both isolates were more tolerant than the others to freeze/thawing in liquid nitrogen. Absorbance peaks are likely chlorophyll a, carotenoids, phycocyanin, scytonemin and MAAs. The Hawaiian isolate was unique in containing a peak at 325 nm that could play a role in DNA protection. The phenotypic similarities in radiation resistance and freeze/thawing resistance among the Hawaiian, Somoan and Negev isolates are likely due to environmental adaptation rather than phylogeny. These data provide environmental parameters of strains in an uninduced state and expand the utility of Chroococcidiopsis as a chassis or source of genetic material for space exploration.