“The figures aren’t very informative. About all I can get out of them is that Junior is going to be a happy hunting ground for uranium, that it’s low in potassium and that it’s no wonder it’s such a lovely little double ice cap of a world.”
He did that deliberately, so that someone could ask him how he knew, and someone, with gratifying wonder, inevitably did.
Vernadsky smiled blandly and said: “Atmospheric radon is ten to a hundred times as high here as on Earth. So is helium. Both radon and helium are produced as by-products of the radioactive breakdown of uranium and thorium. Conclusion: Uranium and thorium minerals are ten to a hundred times as copious in junior’s crust as in Earth’s.
“Argon, on the other hand, is over a hundred times as low as on Earth. Chances are Junior has none of the argon it originally started with. A planet of this type has only the argon which forms from the breakdown of K 40, one of the potassium isotopes. Low argon; low potassium. Simple, kids.”
One of the assembled groups asked, “What about the ice caps?”
Cimon, who knew the answer to that, asked, before Vernadsky could answer the other, “What’s the carbon dioxide content exactly?”
“Zero point zero one six emm emm,” said Vernadsky.
Cimon nodded, and vouchsafed nothing more.
“Well?” asked the inquirer impatiently.
“Carbon dioxide is only about half what it is on Earth, and it’s the carbon dioxide that gives the hothouse effect. It lets the short waves of sunlight pass through to the planet’s surface, but doesn’t allow the long waves of planetary heat to radiate off. When carbon dioxide concentration goes up as a result of volcanic action, the planet heats up a bit and you have a carboniferous age with oceans high and land surface at a minimum. When carbon dioxide goes down as a result of the vegetation refusing to lei a good thing alone, fattening up on the good old see-oh-two and losing its head about it, temperature drops, ice forms, a vicious cycle of glaciation starts, and voilà— ”