One of the first books I read as a boy was H. G. Wells's 1901 fable, The First Men in the Moon. The men land in an apparently barren and lifeless crater, just before the lunar dawn; then, as the sun rises, they realize there is an atmosphere; they spot small pools and eddies of water, and then little round objects scattered on the ground. One of these, as it is warmed by the sun, bursts and reveals a sliver of green. ("'A seed,' says Cavor . . . and then, very softly, 'Life!'") They light a piece of paper and throw it onto the surface of the moon - it glows and sends up a thread of smoke, indicating that the atmosphere, though thin, is rich in oxygen, and will support life as they know it.
This, then, was how Wells conceived the prerequisites of life: water, oxygen, and a source of energy (sunlight). "A Lunar Morning," the eighth chapter in his book, was my first introduction to astrobiology.
