"But we didn't—and neither did they.
"Therefore, they, too, have a colony in that system!"
The Speaker said: "Where? Therbis is the only planet with—" His voice trailed off as he suddenly saw the truth.
Parmay nodded. "All this time, we've been assuming that the aliens were after the same planets we were. But every bit of evidence indicates that they live on the ammonia-methane giants!"
He paused to light a cigarette, then went on: "Alina Starrnel, my wife, has done some checking on the conditions that obtain in such an atmosphere. Alina—" he nodded toward her.
She looked at them from her cool green eyes. "The atmospheres of ammonia-methane giants are such that the surface suffers from almost unbelievable electric storms. Every sunspot on the primary, every wind, every slight change in temperature causes lightnings and electrical displays such as we on Earth can't imagine. The atmosphere itself is a semi-conductor.
"Therefore, it would be almost impossible for them to have radio communication as we know it.
"There are two reasons why metals are not used for construction on such planets. One: the heavy, metal-bearing core of the giants is buried beneath thousands of miles of ice. Two: metals wouldn't stand the strain. At the temperatures prevailing on those planets, most metals are so brittle that they'd shatter under the loads that the unimaginable gravitational pull would cause.
"Plastics are a different matter. Any life that would evolve on such a world would be able to synthesize hard, tough materials in its own body. With plenty of carbon, hydrogen, and nitrogen around, they would have to find some way of making building materials from organic compounds. Actually, they're probably not plastics as we know them; possibly they wouldn't even stand up at normal room temperature on Earth."