"No," said O'Mallory dully. "We can't figure out where the hydrogen's disappearing to, and anyway it shouldn't make that much difference. The energy output down there's about what it's supposed to be, you know."
Gilchrist stood trying to think. His brain felt gelid.
But damn it, damn it, damn it, there must be a rational answer. He couldn't believe they had blundered into an ugly unknown facet of the cosmos. Natural law was the same, here or in the farthest galaxy—it had to be.
Item, he thought wearily. The pile was operating as usual, except that somehow hydrogen was being lost abnormally fast and therefore the pump had to bring in more from Triton's air. But—
—Item. That couldn't be due to a leak in the heating pipes, because they were still at their ordinary pressure.
—Item. The gas in the pipes included some radioactive isotope. Nevertheless—
—Item. It could not be hydrogen-3, because the pile was working normally and its neutron leakage just wasn't enough to produce that much. Therefore, some other element was involved.
Carbon? There was a little methane vapor in Triton's atmosphere. But not enough. Anyway, carbon-13 was a stable isotope, and the pile-room conditions wouldn't produce carbon-14. Unless—
Wait a minute! Something flickered on the edge of awareness.
Danton had buttonholed O'Mallory. "We were talking about using the battery banks," he said.