Life underground during the summer cycle on the moon known as Mu-Beta-Prime sets it apart from all other worlds in the galaxy. Nowhere else does Mankind live for so long in mortal fear of their mother sun. Other planets might have an occasional dust storm, some asteroids are only partially terra-formed. and a moon here or there has its sun blotted out by their mother planet for a week or two, forcing its inhabitants to live in the dark. But only on Mu-Beta-Prime, the dismal moon of the gas giant planet MuArae-Beta, does their sun—known as Cervantes—actually and flat out try to kill them.
The summer cycle begins on Beta-Prime when Cervantes first peeks out from behind the shadow of MuArae-Beta. It then sets about the brutal task bathing the moon's surface with cosmic radiation. Plants growing there have been bioengineered to survive the onslaught, and its range of similarly man-made native animals more or less learn how to live for fifteen days in the glare of deadly sunlight.
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But a human being, no matter how jacked-up they are on animal DNA, wouldn't survive more than two cycles on Mu-Beta-Prime while facing the full bore of its sun. Thus, after each and every two week winter cycle, two weeks of underground living begin. Trade and commerce grind to a halt, and an unregulated, unreported and untaxed system of survival takes over. In shadowy caverns and warehouses buried deep, men and women isolate themselves in small groups, relying on those they trust the most to keep them company, and keep them alive.