filter and not tear our lungs apart."

"A thought, Richard. Suppose we find nickel carbonyl. That's harmless until it is catalyzed by carbon. Then it's worse than phosgene."

"There are lots of deadly ingredients we could find," I admitted with some bitterness. "Gases in solid toxic form—tiny dust granules which would pass right through the filters into our lungs. Jupiter's atmosphere may well be composed entirely of gases in solid phase."

"Let's hope not, Richard."

"We've been talking about lung corrosives," I said, relentlessly. "But our space suits are not impermeable, you know. There are gases which injure the skin, causing running sores. Vesicant gases. The fact that there are no vesicants on Io and Europa doesn't mean we won't encounter them here. And there are nerve gases which could drive us mad in less time than it takes to—"

"Richard, you always were an optimist."

I stared at her steadily for an instant; then shrugged. "All right, Joan. I hope you won't fall down on any of the tests. We've got to project an ion detector, a barometer and a moist cloud chamber outside the ship through a vacuum suction lock, in addition to the atmosphere samplers. And we've got to bandage that face wound before you bleed to death."

CHAPTER III WHAT THE CAMERA SHOWED

A half hour later we had our recordings. Joan sat facing me on the elevated pilot dais, her head swathed in bandages. Dawson and the two other members of our crew stood just beneath us, their faces sombre in the cube-light.

They had miraculously escaped injury, although Dawson had a badly shaken up look. His hair was tousled and his jaw muscles twitched. Dawson was fifty-three years old, but the others were still in their early twenties—stout lads who could take it.

The fuel unit control pilot, James Darnel, was standing with his shoulders squared, as though awaiting orders. I didn't want to take off. I had fought Joan all the way, but now that we were actually on Jupiter I wanted to go out with her into the unknown, and stand with her under the swirling, star-concealing mist.

I wanted to be the first man to set foot on Jupiter. But I knew now that the first man would be the last. The atmospheric recordings had revealed that there were poisons in Jupiter's lethal cloud 

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