is just tend a computer, give it a stroke or two, andsay, "Nicedoggie," then read off the results. It's not so. What the computer says depends on what you put into it, and I never heard a theoretician face an observation he didn't like without blaming the observer. Never once did I hear him say, "There must be something wrong with the compu-" '
'Hold on,' said Wu. 'Let's not flood this place with recrimination. Have you ever heard me blaming observers?'
'If you didn't like Henry's observations-'
'I'd take them anyway. I don't have any theories about this world.'
'And that's why you'd take whatever he gives you.'
At this point Henry Jarlow walked in with Tessa Wendel close behind. He looked like a cloud making up its mind to rain.
Wendel said, 'Very well, Jarlow, we're all here. Now, tell us. What does it look like?'
'The trouble is,' said Jarlow, 'there isn't enough ultraviolet in the light of this weakling star to raise a sunburn on an albino. I have to work with micro-waves and that tells me, at once, that there's water vapor in the world's atmosphere.'
Wendel shrugged it off with an impatient lift of her shoulders. 'We don't need you to tell us that. A world the size of Earth in a liquid-water range of temperature would surely have water and, therefore, water vapor. That moves it one more notch toward habitability, but only one more thoroughly expected notch.'
'Oh no,' said Jarlow uneasily. 'It's habitable. No question.'
'Because of the water vapor?'
'No. I have something better than that.'
'What?'
Jarlow looked around him at the other four rather grimly, and said, 'Would you say a world was habitable if, in actual fact, it was inhabited?'
'Yes, I think I could bring myself to say that,' said Wu calmly.
'Are you telling me that you can see that it's inhabited at this distance?' asked Wendel sharply.
'Yes, that's exactly what I'm saying, Captain. There's free oxygen in the atmosphere - and in quantity. Can you tell me how that can be without photosynthesis? And can you tell me how you can have photosynthesis without the presence of life? And can you tell me how a planet can be uninhabitable if it has oxygen-producing life on it?'
There was dead silence for a moment, then Wendel said, 'That is so unlikely, Jarlow. Are you sure you didn't mess up the programming?'
And Blankowitz quietly raised her eyebrows at Wu in an unspoken: 'See-e-e-e-e!'
Jarlow said stiffly, 'I have never messed up, as you call it, a programming in my life, but, of course, I'm willing to stand corrected if anyone here feels he is more knowledgeable about atmospheric infrared analysis than I am. It's not my field of expertise, but I did make careful use of Blanc and Nkrumah on the subject.'
Crile Fisher, who had gained considerable self-confidence since the incident involving Wu's bid to return home, did not hesitate to insert his views.
'Look,' he said, 'this will either be confirmed or denied as we get closer, but why don't we assume that Dr Jarlow's analysis is correct and see where that takes us? If there is oxygen in the atmosphere of this world, might we not assume that it's been terraformed?' All eyes turned to look at him. 'Terraformed?' said Jarlow blankly. 'Yes, terraformed. Why not? You have this world that is suitable for life, except that it has the carbon dioxide and nitrogen atmosphere that worlds without life have - like Mars and Venus - and you dump algae into the ocean and pretty soon it's "Goodbye, carbon dioxide," and "Hello, oxygen." Or maybe you do something else. I'm no expert.'
They were still looking at him.
Fisher went on. 'The reason I'm suggesting this is that I remember there was talk about terraforming on the farms on Rotor. I worked there. There were even some seminars on terraforming that I attended because I felt it might have something to do with the hyper-assistance program. It didn't, but at least I heard about terraforming.'
Finally Jarlow said, 'In all you heard about terraforming, Fisher, do you by any chance recall anyone saying how long it would take?'
Fisher spread his arms. 'You tell me, Dr Jarlow. It will save time, I'm sure.'
'All right. It took Rotor two years to get here - if it got here. That means it's been here thirteen years. If all of Rotor were solid algae and it was all dumped into the ocean and lived and grew and produced oxygen, then to get to the present level, where I estimate