And then when the inflight had brought them to a distance from which Erythro's atmosphere could be studied spectroscopically with precision, Insigna said to him, ‘Erythro's atmosphere is a little denser than Earth's and it contains free oxygen - 16 per cent of it, plus 5 per cent argon and the rest nitrogen. There must be small quantities of carbon dioxide, but we haven't detected it yet. The point is, it's a breathable atmosphere.’
‘Sounds better and better,’ said Pitt. ‘Who could have imagined this when you first spotted Nemesis?’
‘Better and better for the biologist. Maybe not very good for Rotor on the whole, though. A sizable content of free oxygen in the atmosphere is a sure indication of the presence of life.’
‘Life?’ said Pitt, momentarily stupefied at the thought.
‘Life,’ said Insigna, boring in, taking an apparent perverse pleasure in stressing the possibilities. ‘And if life, then possibly intelligent life, perhaps even a high civilization.’
17What followed was a nightmare for Pitt. He had not only to live with the terrible apprehension of his own Earth-people pursuing and overtaking him, superior in number certainly, and in technology possibly - but there was an accompanying fear now that was, if anything, greater. They might be approaching and infringing on an old and advanced civilization capable of eradicating them in a moment of absent-minded annoyance as a human being might, without thinking, crush a mosquito that buzzed too near his ear.
As they continued to approach Nemesis, Pitt said to Insigna with a deeply troubled air, ‘Need oxygen truly imply the existence of life?’
‘It's a thermodynamic inevitability, Janus. In an Earth-like planet - and, as nearly as we can tell, Erythro is Earth-like - free oxygen cannot exist, any more than in any Earth-like gravitational field, a rock can be suspended in open air of its own accord. Oxygen, if present in the atmosphere to begin with, would spontaneously combine with other elements in the soil, giving off energy. It would only continue to exist in the atmosphere if some process were to supply energy and continually regenerate free oxygen.’
‘I understand that, Eugenia, but why need the energy-supply process necessarily involve life?’
‘Because nothing has ever been encountered in nature that would do the job, except the photosynthetic action of green plants that make use of solar energy to release oxygen.’
‘When you say “nothing has ever been encountered in nature,” you mean in the Solar System. This is another system with a different sun and a different planet under different conditions. The laws of thermodynamics may still hold, but what if there is some chemical process that we haven't encountered in the Solar System and that is forming the oxygen here?’
‘If you're a betting man,’ said Insigna, ‘don't bet on it.’
What was needed was evidence, and Pitt had to wait for the evidence to appear.
To begin with, Nemesis and Megas turned out to have extremely weak magnetic fields. This created no particular stir for it had been expected, since both star and planet rotated very slowly. Erythro, with a rotational period of twenty-three hours and sixteen minutes (equal to the period of its revolution about Megas), had a magnetic field that was similar, in intensity, to Earth's.
Insigna expressed her satisfaction. ‘At least we don't have to worry about dangerous radiation effects from intense magnetic fields, especially since Nemesis' stellar wind is bound to be much less intense than that of the Sun. That's good, because it means we might be able to detect the presence or absence of life on Erythro at a distance. Technological life, anyway.’
‘Why's that?’ asked Pitt.
‘It's not at all likely that a high level of technology can be reached without copious use of radio-wave radiation, which would be speeding away from Erythro in all directions. We ought to be able to differentiate between it and any random radio-wave radiation from the planet itself, when such natural radiation is minor, considering that its magnetic field is weak.’
Pitt said, ‘I've been thinking that this may not be necessary; that we can reason out Erythro's lifelessness, even though it does have an oxygen atmosphere.’
‘Oh? I'd like to hear how that might be done.’
‘I've thought this out. Listen! Didn't you say that tidal influences slow the rotations of Nemesis, Megas and Erythro? And didn't you say that, as a result, Megas has moved farther from Nemesis, and Erythro has moved farther from Megas?’
‘Yes.’
‘Therefore, if we look into the past, Megas was once closer to Nemesis and Erythro was closer to Megas and to Nemesis, too. That means that Erythro was far too warm for life to begin with, and may only have become hospitable to life recently. There might not have been enough time for a technological civilization to develop.’
Insigna laughed gently. ‘Good point. I mustn't underestimate your astronomical ingenuity - but not good enough. Red dwarf stars have a long life and Nemesis might easily have been formed in the very youth of the Universe - say, fifteen billion years ago. The tidal influence would have been very strong at first, when the bodies were closer together, and most of the driving apart may have taken place in the first three or four billion years. The tidal influence decreases as the cube of the distance and, in the last ten billion years or so, there would not have been much change and that would be plenty of time for several technological civilizations to be built up, one after the other. No, Janus, let's not speculate. Let's wait and see if we can detect radio-wave radiation, or not.’
—Closer still to Nemesis.
It was a tiny red orb now to the unaided eye, but its dimness could be looked at without trouble. To one side, Megas was visible as a ruddy dot. In the telescope, it showed at something less than half-phase as a result of the angle it made with Rotor and with Nemesis. Erythro could be made out in the telescope, too, as a dimmer crimson dot.
It grew brighter with time, and Insigna said, ‘It's good news for you, Janus. No suspicious radio-wave radiation of possibly technological origin has yet been detected.’
‘Wonderful.’ Pitt felt the wave of relief as though it were a physical warmth washing over him.
‘Don't leap, though,’ said Insigna. ‘They might use less radio-wave radiation that we might expect. They might shield it very well. They might even use something else in place of radio waves.’
Pitt's mouth quirked into a small half-smile. ‘Are you suggesting that seriously?’
Insigna shrugged uncertainly.
Pitt said, ‘Because if you're a betting woman, don't bet on it.’
—Closer still to Nemesis, and Erythro was now a large orb to the unaided eye, with bloated Megas near it, and Nemesis on the other side of the Settlement. Rotor had adjusted its velocity to keep pace with Erythro, which, through the telescope, showed drifting broken clouds in the familiar spiral shapes of a planet of Earth-type temperature and atmosphere, and, therefore, it should be counted on as possessing an at least vaguely Earth-like climate.
Insigna said, ‘There are no signs of light on the night-side of Erythro. That should please you, Janus.’
‘The absence of light is not consistent with a technological civilization, I suppose.’
‘It certainly isn't.’
‘Let me play devil's advocate, then,’ said Pitt. ‘With a red sun and dim light, wouldn't a civilization produce a dim artificial light as well?’
‘It might be dim in the visible region, but Nemesis is rich in the infrared and we would expect artificial light to be similarly rich. What infrared we detect, however, is planetary. It appears, more or less equally, over the entire land surface, whereas artificial light would have patterns, coming off richly in population concentrations, sparsely elsewhere.’
‘Then forget it, Eugenia,’ said Pitt buoyantly. ‘There is no technological civilization. It might make Erythro less interesting in some ways, but you can't want us to face our equals, or, perhaps, our superiors. We would have to leave and go elsewhere, and we have nowhere else to go, and perhaps an insufficient energy supply to get there if we did. As it is, we can stay.’