take a pretty big one to damage a servo bearing," Cade
commented.

"That could hurt," Cowalczk admitted, "but there was only one of them."

"You mean only one hit our gear," Lehman said. "How many missed?"

Nobody answered. They could all see the Moon under their feet. Small
craters overlapped and touched each other. There was--except in the
places that men had obscured them with footprints--not a square foot
that didn't contain a crater at least ten inches across, there was not a
square inch without its half-inch crater. Nearly all of these had been
made millions of years ago, but here and there, the rim of a crater
covered part of a footprint, clear evidence that it was a recent one.

After the sun rose, Evans returned to the lava cave that he had been
exploring when the meteor hit. Inside, he lifted his filter visor, and
found that the light reflected from the small ray that peered into the
cave door lighted the cave adequately. He tapped loose some white
crystals on the cave wall with his geologist's hammer, and put them into
a collector's bag.

"A few mineral specimens would give us something to think about, man.
These crystals," he said, "look a little like zeolites, but that can't
be, zeolites need water to form, and there's no water on the Moon."

He chipped a number of other crystals loose and put them in bags. One of
them he found in a dark crevice had a hexagonal shape that puzzled him.

One at a time, back in the tractor, he took the crystals out of the bags
and analyzed them as well as he could without using a flame which would
waste oxygen. The ones that looked like zeolites were zeolites, all
right, or something very much like it. One of the crystals that he
thought was quartz turned out to be calcite, and one of the ones that he
was sure could be nothing but calcite was actually potassium nitrate.

"Well, now," he said, "it's probably the largest natural crystal of
potassium nitrate that anyone has ever seen. Man, it's a full inch
across."

All of these needed water to form, and their existence on the Moon
puzzled him for a while. Then he opened the bag that had contained the
unusual hexagonal crystals, and the puzzle resolved itself. There was
nothing in the bag but a few drops of water. What he had taken to be a
type of rock was ice, frozen in a niche that had never been warmed by
the sun.

* * * * *

The sun rose to the meridian slowly. It was a week after s