Warm-Blooded Plants: Zero-g, Zero-T, and Zero-P

There are three principal obstacles to be overcome in adapting a terrestrial species to life in space. It must learn to live and be happy in zero-g, zero-T, and zero-P, that is to say, zero-gravity, zero-temperature, and zero-pressure. Of these, zero-g is probably the easiest to cope with, although we are still ignorant of the nature of the physiological hazards which it imposes. To deal with zero-T is simple in principle although it may be complicated and awkward in practice. Fur and feathers provide even better insulation in a vacuum than they do {105} in air or in water. Creatures adapted to space must learn to balance the energy generated by their metabolism and by absorption of sunlight or starlight against the energy lost by radiation from their surfaces. Some active control of the radiating surfaces will probably be required. But the low temperature of the environment makes the regulation of an organism's internal temperature easier rather than more difficult. It is easier to keep warm on Pluto than to keep cool on Venus. Once a species has learned to keep warm on Pluto, it will soon be able to keep warm almost anywhere in the universe. The main innovation which the adaptation of life to zero-T requires is that plants as well as animals must become warm-blooded. It seems to be only a curious historical accident that the natural evolution of life on earth produced warm-blooded animals before it produced warm-blooded plants. Only because of this poverty of invention in the plant kingdom do we find the coasts of our Arctic Ocean thinly populated with polar bears rather than thickly populated with living greenhouses. A warm-blooded plant, growing around itself a living greenhouse as effortlessly as a polar bear grows fur or a whale blubber, could spread quickly over the plains of Pluto.

But the most important and most difficult part of the adaptation of life to the cosmos is the adaptation to zero-P. It is only by adapting to zero-pressure, by learning to live in vacuum, that life can be liberated from narrow and malodorous confinement in space capsules and space suits. The move of life from air to vacuum is as fundamental and as liberating as the move which our ancestors made from water to air half a billion years ago. I cannot pretend to have understood the problems of adaptation in detail. I could not define the specifications of a zero-P potato precisely enough for a genetic engineer to sit down and begin working out the DNA sequences to put into its chromosomes.