By circling the planet from east to west they kept to the daylight side most of the time, and as the hours passed they were able to get most of their pictures and reports on the geography, climate and other conditions. Their spectro-analyzer showed considerable mineral deposits in many of the places over which they passed. They saw plenty of vegetation and Jon exclaimed about its coloring. "Must be fall here," Jak explained. "Unless, of course, those plants don't contain chlorophyll, which I doubt." But nowhere did they see anything that looked like the works of intelligent beings. Like Planet Two, there was no sign of people anywhere. When they became so tired they could no longer keep awake, Jon set the ship into a higher, safer orbit, and they all went to bed. Their father had awakened only once during the day, and then only for a few minutes, nor had his wife allowed him to talk, greatly as the boys, especially, desired it. * * * * * After breakfast the next morning Jon maneuvered the ship down closer to the surface and they completed exploring the planet, taking their pictures and recordings. Jak made tests and reported the atmosphere not poisonous, although so scant they would have to wear suits most of the time when outdoors. "It's lots better than Mars, but not near as dense as Terra or Two back there," he told Jon. "Temp's below freezing, but I imagine it'll get warmer when the sun's nearer noon here." "Humans can adapt themselves to living here, then." Jon's voice was joyful. "They've already colonized planets worse than this, as far as temperature and air are concerned." "Yes, the human animal seems to be marvelously adaptable to almost any conditions not actually poisonous," Jak said admiringly. "There's even a colony of people from the High Andes of Souamer living on Mars now, without domes." "They could transport those Andean Indians to Mars direct because they were used to living in the rarefied atmosphere of the high mountains, eh?" "That's right. Those Indians would have suffocated at sea level back on Terra. Indeed, they seldom went down the mountains below ten thousand feet because of the discomfort. On Mars, they had some difficulty at first, but I understand the second generation born there are perfectly at home." Jon's blue eyes had been watching his detectors, even while his ears had been listening to Jak's explanations. So far he had not discovered any of that strange fuel-metal--if it was fuel--they had found on Two. He spoke of this now to his brother. "Wonder if those people didn't leave any caches here on Three, or what?" "Maybe they didn't like cold weather." Jak grinned. "More likely, though, either we haven't come close enough to detect it, or else they may only have made a cache on one planet in a system." "That's probably it. I've been watching for it all the way in, and 'Annie' didn't chirp at all. Well, do we land and see what the joint is like?"