"Das wasser," cut in Putz. "Vere goes dot?"

"Even a chemist knows that!" scoffed Jarvis. "At least on earth. Here I'm not so sure, but on earth, every time there's a lightning flash, it electrolyzes some water vapor into hydrogen and oxygen, and then the hydrogen escapes into space, because terrestrial gravitation won't hold it permanently. And every time there's an earthquake, some water is lost to the interior. Slow — but damned certain." He turned to Harrison. "Right, Cap?"

"Right," conceded the captain. "But here, of course — no earthquakes, no thunderstorms — the loss must be very slow. Then why is the race dying?"

"The sun-power plant answers that," countered Jarvis. "Lack of fuel! Lack of power! No oil left, no coal left — if Mars ever had a Carboniferous Age — and no water-power — just the driblets of energy they can get from the sun. That's why they're dying."

"With the limitless energy of the atom?" exploded Harrison.

"They don't know about atomic energy. Probably never did. Must have used some other principle in their space-ship."

"Then," snapped the captain, "what makes you rate their intelligence above the human? We've finally cracked open the atom!"

"Sure we have. We had a clue, didn't we? Radium and uranium. Do you think we'd ever have learned how without those elements? We'd never even have suspected that atomic energy existed!"

"Well? Haven't they — ?"

"No, they haven't. You've told me yourself that Mars has only 73 percent of the earth's density. Even a chemist can see that that means a lack of heavy metals — no osmium, no uranium, no radium. They didn't have the clue."

"Even so, that doesn't prove they're more advanced than we are. If they were more advanced, they'd have discovered it anyway."