Hard-science yarn investigating intelligent creatures who inhabit a remote comet-planetoid whose surface temperature (per the title) is 30 degrees above absolute zero--from the author of Timemaster, Martian Rainbow, etc. In 2029, an impoverished and overpopulated Earth, hoping for high-powered help, mounts an expedition to contact the alien ``keracks''--a tiny, shrimplike, hive-minded race who've built cities all over their chilly world. Though ``telebots''--they themselves are much too big and hot to contact the keracks directly--the humans explore the city Camalor in the company of the local genius, wizard Merlene. The native biology, ingeniously, is driven by energy derived from cosmic rays, free radicals, and radioactivity (at this distance, the sun is only a bright star, and photosynthesis won't work). The keracks have a puzzling warlike, medieval, royalist social structure, the reasons for which only slowly become clear. Biochemistry fueled by radioactivity is the key: driven by instinct, the Camalor queen is constructing a hydrogen bomb that will blow the city apart, thus seeding outer space with spores, someday to start a new civilization elsewhere. But can the humans escape the explosion, or save Merlene from her fate? Despite the whiz-bang chemistry and physics, it isn't much of a plot; nor is it clear how life could get started under such conditions, let alone thrive. The indistinguishable characters don't help. Solid fare for Forward fans, then; slim pickings for those desirous of more orthodox novelistic virtues.