Oxygen came in ample quantities from the dissociation of water. Ultraviolet light from the Sun produced the dissociation, yielding nearly a kilogram of oxygen per day per square meter of exposed area. Ten square meters gave sufficient oxygen for a man. Nitrogen and carbon were problems, particularly nitrogen. The water from below had a lot of carbon dioxide dissolved in it, however. Really, it was soda. Less nitrogen, but enough, also came up with the water. Photosynthesis was quick and efficient, enabling a subsistence diet to become established. Trace elements, vitamins, and so on, were still imported from Earth. Even this dependence could have been overcome in time, but the time available for research on the Moon was now running out. As a NASA spokesman succinctly put it, the nation had acquired a Martian-wise capability.
it had come as a shock many years earlier to discover how very similar the Martian surface is to the Moon. This should really have been obvious from the beginning. It should have been obvious that the general dappled appearance of Mars is the same phenomenon as the “Man in the Moon” pattern of the lunar surface. The pattern comes from an overlapping of circular patches, like the “seas” or maria of the Moon, themselves produced by the large-scale impacts of huge meteorites, craters on the biggest scale of all. The canals that many observers thought they had seen turned out to be mere chains of craters. The human eye always tends to connect together a number of dots along a line, to see them as a complete line. This became obvious from the first fly-by pictures. Mars was simply a larger-scale version of the Moon.
This was why the lunar laboratory was so important. Much the same conditions could be expected on Mars, the same glaciers, the same water problems. Apart from the sheer dynamics of reaching Mars, demanding much more powerful boosters, apart from the length of the voyage—several months instead of days—most local problems should be less difficult on Mars. There would be somewhat stronger gravity, which was an advantage. The Martian atmosphere would remove the solar X-rays against which all lunar scientist-explorers had to be endlessly shrouded. There was some oxygen in the Martian atmosphere. Compressors would therefore give an adequate oxygen supply. The Martian atmosphere would reduce electrostatic effects so that dust would not be quite such a bad problem. The Martian atmosphere seemed to be an advantage in every way.
Both the atmosphere and the white polar caps of Mars were well understood now. With water coming up occasionally from below, exactly as on the Moon, thin polar caps of hoarfrost were just what one would expect. Martian gravity is intermediate between Earth and Moon. Terrestrial gravity is strong enough for the Earth to have retained most of the water squeezed from its interior throughout the eons. At the opposite extreme, the very weak lunar gravity of the Moon permits it to retain no surface water. Mars lies between. Mars holds water, but not for long. There is always a little water on the surface, water recently come from below which has not yet had time enough to escape away into space. The oxygen comes, of course, from dissociation of the water by sunlight, and carbon dioxide and nitrogen also come up with the water. The clouds observed from time to time by early astronomers were simply occasional squirts, released by an impacting meteorite from without. Mars was more subject to bombardment than the Moon, being nearer the asteroidal belt. Protecting spacecraft from impact was a serious difficulty, one that it didn’t pay to think about too closely.
Mars was expected to be similar to the Moon in another respect, one which might well have served as a warning. A theoretical speculation dating from the 1960s was now entirely confirmed. Earth and Venus are both built from very roughly equal amounts of rock and unoxidized metals, particularly iron. The two components are largely separate, with the metals on the inside, the rocks on the outside, which raises the problem of how they got that way. Given a homogeneous, solid mixture of rock and metal in the first place, the metal would not sink to the middle. So much was realized. Perhaps when the planets were formed from a hot gas the metal was the first to condense. Then the rocks condensed later around the metal. This would solve the problem in one move. The trouble was that calculation showed rock and metal should both condense more or less together, as a mixture.
The solution came in a most surprising way. It was natural in the first calculations to assume the temperature of the cooling gases went steadily lower and lower as time went on. But this apparently reasonable hypothesis wasn’t right. The temperature first went down, then it lifted for a while, before taking a final plunge in the last cooling phase. The temperature curve had first a minimum, then a maximum, after which it declined away. Condensation of rock and metal occurred equally at the minimum. The surprise came with a calculation which showed that although the rock and metal condensed together, they would not evaporate together at the succeeding temperature maximum. The metal would evaporate, but not the rock. So in the final decline of temperature it would be the metal that would condense bodily around the rock. Earth and Venus had the metal and rock separate, all right, but the wrong way round, the metal on the outside, not the inside.
This arrangement—an inner ball of rock surrounded by a substantially more dense shell of metal, the shell with a similar mass to the ball—was quite unstable, however. The shell collapsed inward, so that shell and ball interchanged themselves. The whole Earth was turned inside out, like Baron Munchausen’s fox. The same was true for Venus, but not for the Moon or Mars. Neither the Moon nor Mars had very much metal, and what they had was still outside the rock. Their outer metallic shells had never become massive enough for the same instability to have occurred. A lot turned on the difference, on Mars having its metal on the outside.
With space technology developed to a state of planet-wise capability, and with the mass of data collected from the many telepuppets now in orbit around the planet, the stage was set for a manned mission to Mars. Although the astronauts assigned to the mission were as dedicated as ever, they were naturally much worried by the sterility problem.
The first lunar rockets had possessed no more than a certified sterility. Used for soft landings, they were dealt with by simple ethylene-oxide techniques. The priority was soon off the sterility problem, however, so far as the Moon was concerned. Cynthia turned out to be herself entirely sterile. No wonder, with the drenching of X-rays she was receiving, and with the cold on her backside and the heat on her frontside. Thereafter nobody had any worries about “ejecta” on the Moon.
Mars was another breed of cats. Twenty years earlier, Mars had already been declared a biological preserve. This had been agreed internationally. As one cognizant biologist put it, “The mere suggestion that fecal material might be jettisoned under conditions which would contaminate the surface is symptomatic of attitudes which fail to give appropriate consideration of exobiological objectives.” Such irresponsible procedures were condemned, totally and emphatically. In plain language, readily understandable to one and all, this meant you couldn’t shit on Mars.
A tremendous amount of research, it is true, had been put into the development of space suits equipped with really efficient “biological barriers,” as the pundits of NASA put it. Be this as it may, all astronauts found these things the very devil. It seemed much simpler to go chronically constipated.