On the second day, Nolan went in search of permafrost. Their instruments faithfully recorded everything they needed except such items as this. Nolan found permanent ice in a valley of the northern mountains. It was perpetually frozen ground which might not have thawed in a thousand thousand years. He dug down through surface ice to the permanently frozen soil beneath it. That soil was not desert sand. And preserved in it Nolan found the blackened roots of plants, and the blackened blades of something like grass, and even some small, indefinite objects which had been seeds or fruit. They hadn't died with the planet. They were far older than that catastrophe. But they were proof that once this world lived and throve. During what was left of the day-light, Nolan and Kelley went south to a river gorge and photographed it for the record. The river had cut a gorge a full two hundred feet deep in the wind-deposited dust which was everywhere. There were now-dry gullies which undercut the dune-sides and at times dumped mud into the slowly flowing liquid of the river. There were no colorings save dust and mud. The river itself was mud. It flowed very, very slowly and without elation. They came back depressed. An airless planet holds no life, but it defies life to establish itself. A methane-ammonia planet fights the intrusion of men with monstrous frigid storms. But this world was designed for life. That it was dead was tragedy. Its rivers flowed sullen, syrupy mud which moved reluctantly toward the lifeless seas. Kelley wouldn't look at the sunset this second night. He went into the camp and turned on music. Crawford watched for a little while only. There were clouds. There were breezes. One knew that here and there rain fell in gentle showers which should have nourished grasses and flowers and filled the air with fragrance. But instead it fell upon impalpable dust and turned it to mud which flowed slowly into gullies and into rivers which were also mud and moved onward, until perhaps after years the soil would become part of a mud-bank in the ocean. Nolan came into the foam-walled house and said shortly, "We'll finish up tomorrow and leave." Kelley said abruptly. "Nobody's made any guess about why everything died, here. But we all know!" Crawford said reflectively, "It must've taken a lot of intelligence to murder this planet. When d'you suppose it happened?" "Ten thousand--twenty thousand years ago," said Nolan. "The whole place must have been radioactive, air and all. But if they used cobalt the background count could be down to 3.9 in ten or twenty thousand years." "We haven't," said Kelley, "seen any craters. Even the pictures from out in space didn't show bomb-craters."