hem on and read the illuminated dial on the alpha counter.
Plenty high, as was natural. But no danger there--alpha particles
couldn't penetrate the space suits. Then, his hand clammy inside the
space glove, he switched on the other meter. The gamma count was far
below the alpha, but there were too many of the rays around for comfort.
Inside the helmet his face turned pale.

There was no immediate danger. It would take many days to build up a dose
of gamma that could hurt them. But gamma was not the only radiation. They
were in space, fully exposed to equally dangerous cosmic radiation.

The Planeteers had gathered while he read the instruments. Now they stood
watching him.

They knew the significance of what he had found.

"I ought to be busted to recruit," he told them. "I knew this asteroid
was thorium and that thorium is radioactive. If I had used my head, I
would have added nuclite shielding to the list of supplies the _Scorpius_
provided. We could have had enough of it to protect us while around our
base, even if we couldn't be protected while working on the charges. That
would at least have kept our dosage down enough for safety."

"No one else thought of it, either, sir," Koa reminded him.

"It was my job to think of it, and I didn't. So I've put us in a time
squeeze. If the _Scorpius_ gets back soon, we can get the shielding
before our radiation dosage has built up very high. If the ship doesn't
come back, the dosage will mount."

He looked at them grimly. "It won't kill us, and it won't even make us
very sick. I'll have the ship take us off before we build up that much
dosage."

Santos started. "But, sir! That means--"

"I know what it means," Rip stated bitterly. "It means the ship has got
to return in time to give us some nuclite shielding, or we'll be the
laughingstock of the Special Order Squadrons--the detachment that started
a job the spacemen had to finish!"

CHAPTER SEVEN

Earthbound!

There was something else that Rip didn't add, although he knew the
Planeteers would realize it in a few minutes. Probably some of them
already had thought of it.

To move the asteroid into a new orbit, they were going to fire nuclear
bombs. Most of the highly radioactive fission products would be blown
into space, but some would be drawn back by the asteroid's slight
gravity. The craters would be highly radioactive, and some radioactive
debris was certain to be scattered around, too. Every particle