How Kort had turned the trick was not completely inconceivable. In making starch from carbon-dioxide and moisture under the action of sunlight, the green plantlife of Mars produces oxygen just as Earthly vegetation does. But instead of freezing it lavishly to the air, many of those Martian growths, hoarding the essentials of life on a dying world, compress their oxygen into cavities in stem and root and underground capsule, to support later a slow tissue-combustion like that of warm-blooded animals, thus protecting their vitals from cold and death. Despoiling these stores of oxygen with a pointed metal pipette attached to a greedily sucking compressor, was a known means of emergency survival on Mars. Thus you could laboriously replenish the oxygen flasks for your air-hood. Simple--yes. But tedious, grinding, endless. Dayton could imagine. Food and shelter were also necessary. But under thickets there is a five-foot depth of fallen vegetation, dry, felty, slow to decay in this climate, accumulating autumn after autumn for Martian centuries. In this carpet are those oxygen-holding capsules and roots, often broken, freeing their contents for the spongy surrounding material to hold. There too grow much green algae--simpler plants of the same function. There are the fruit and seed-pods of the surface growths, sheltered from cold. And there, the remaining animal life has retreated. Fuzzy, tawny things that twitter; fat, mammal-like excavators that never care to see the sky, and many-jointed creatures that resemble Earthly ants only in their industry and communal skills. Above ground they build their small, transparent air-domes--bubblelike structures formed of hardened secretion from their jaws. There they shelter their special gardens and sun their young. So, for a man able to borrow methods unlike his human heritage, there were ways to keep alive in the raw Martian wilds. * * * * * Once, Lorring, the physician, said to Joe Dayton, "Kort must have burrowed, too--like a bear. Is that human? Of course the tip of the Syrtis Major triangle here at Port Laribee is far north. But even if he could have gotten all the way to the tropics, the nights are still bitter. Even so, the big question is not how he lived like he did, but why?" Yes, this was a point which Dayton had often wondered about, frowning with thick, dark brows, while his wide mouth smiled quizzically above a generous jaw. What had impelled Kort to a solitude far deeper than that of an old-time hermit or desert-rat? Had he been a great child lumbering by instinct through the misfit fogs of his mind to a place where he felt at peace? Dayton favored another explanation as the main one.