then thought better of it. He stood quietly near the control panel and
watched.

The air lock hissed, then slid open. A Martian stood in the entryway, a
case on his shoulder. Rip watched him with interest. He had seen Martians
before, on the space platform, but he had never gotten used to them. They
were human, still....

He tried to figure out, as he had before, what it was that made them
strange. It wasn't the blue-whiteness of their skins nor the very large,
expressionless eyes. It was something about their bodies. He studied the
Martian's figure carefully. He was slightly taller and more slender than
the average earthman, but his chest measurements would be about the same.
Nor were his legs very much longer.

Suddenly Rip thought he had it. The Martian's legs and arms joined his
torso at a slightly different angle, giving him an angular look. That was
what made him look like a caricature of a human, although he was human,
of course--as human as any of them.

Rip saw that other Martians were in the air lock, all carrying cases of
various sizes and shapes. They came through into the control room and put
them down, then turned without a word and hurried back into the lock.
They were all breathing heavily, Rip noticed. Of course! The artificial
atmosphere inside the spaceship must seem very heavy and moist to them,
after the thin, dry air of Mars.

The lock worked, and the Martians were replaced by others. They, too,
deposited their cases. But these cases were bigger and heavier. It took
four Martians to carry one, which meant they weighed close to half a ton