The planet named Niflheim is the fourth planet of Nu Puppis, right angle 6:36, declension −43:09; B8 type star, blue-white and hot, 148 light years distant from Earth, which will require a speed in excess of light to reach it.

Niflheim is 462,000,000 miles from its primary, a little less than the distance of Jupiter from our sun. It thus does not receive too great a total amount of energy, but what it does receive is of high potential, a large fraction of it being in the ultraviolet and higher frequencies. (Watch out for really super-special sunburn, etc., on unwarned personnel.)

The gravity of Niflheim is approximately 1 g, the atmospheric pressure approximately 1 atmosphere, and the average ambient temperature about −60° C; −76° F.

2 Atmosphere

The oxidizer in the atmosphere is free fluorine (F₂) in a rather low concentration, about 4 or 5 percent. With it appears a mad collection of gases. There are a few inert diluents, such as N₂ (nitrogen), argon, helium, neon, etc., but the major fraction consists of CF₄ (carbon tetrafluoride), BF₃ (boron trifluoride), SiF₄ (silicon tetrafluoride), PF₅ (phosphorous pentafluoride), SF₆ (sulphur hexafluoride) and probably others. In other words, the fluorides of all the nonmetals that can form fluorides. The phosphorous pentafluoride rains out when the weather gets cold. There is also free oxygen, but no chlorine. That would be liquid except in very hot weather. It sometimes appears combined with fluorine in chlorine trifluoride. The atmosphere has a slight yellowish tinge.

3 Soil and Geology

Above the metallic core of the planet, the lithosphere consists exclusively of fluorides of the metals. There are no oxides, sulfides, silicates or chlorides. There are small deposits of such things as bromine trifluoride, but these have no great importance. Since fluorides are weak mechanically, the terrain is flattish. Nothing tough like granite to build mountains out of. Since the fluoride ion is colorless, the color of the soil depends upon the predominant metal in the region. As most of the light metals also have colorless ions, the colored rocks are rather rare.

4 The Waters Under the Earth

They consist of liquid hydrofluoric acid (HF). It melts at −83° C and boils at 19.4° C. In it are dissolved varying quantities of metallic and nonmetallic fluorides, such as boron trifluoride, sodium fluoride, etc. When the oceans and lakes freeze, they do so from the bottom up, so there is no layer of ice over free liquid.

5 Plants and Plant Metabolism

The plants function by photosynthesis, taking HF as water from the soil, and carbon tetrafluoride as the equivalent of carbon dioxide from the air to produce chain compounds, such as:

and at the same time liberating free fluorine. This reaction could only take place on a planet receiving lots of ultraviolet because so much energy is needed to break up carbon tetrafluoride and hydrofluoric acid. The plant catalyst (doubling for the magnesium in chlorophyll) is nickel. The plants are colored in various ways. They get their metals from the soil.

6 Animals and Animal Metabolism

Animals depend upon two main reactions for their energy, and for the construction of their harder tissues. The soft tissues are about the same as the plant molecules, but the hard tissues are produced by the reaction:

resulting in a teflon boned and shelled organism. He’s going to be tough to do much with. Diatoms leave strata of powdered teflon. The main energy reaction is:

The blood catalyst metal is titanium, which results in colorless arterial blood and violet veinous, as the titanium flips back and forth between tri and tetravalent states.

7 Effect on Intruding Items

Water decomposes into oxygen and hydrofluoric acid. All organic matter (earth type) converts into oxygen, carbon tetrafluoride, hydrofluoric acid, etc., with more or less speed. A rubber gas mask lasts about an hour. Glass first frosts and then disappears. Plastics act like rubber, only a little slower. The heavy metals, iron, nickel, copper, monel, etc., stand up well, forming an insoluble coat of fluorides at first and then doing nothing else.

8 Why Go There?

Large natural crystals of fluorides, such as calcium difluoride, titanium tetrafluoride, zirconium tetrafluoride, are extremely useful in optical instruments of various forms. Uranium appears as uranium hexafluoride, all ready for the diffusion process. Compounds of such nonmetals as boron are obtainable from the atmosphere in high purity with very little trouble. All metallurgy must be electrical. There are considerable deposits of beryllium, and they occur in high concentration in its ores.

Prologue

On Satan’s Footstool

The big armor-tender vibrated, gently and not unpleasantly, as the contragravity field alternated on and off, occasionally varying its normal rate of five hundred to the second when some thermal updraft lifted the vehicle and the automatic radar-altimeter control acted to alter the frequency and lower it again. Sometimes it rocked slightly, like a boat on the water, and, in the big screen which served in lieu of a window at the front of the control cabin, the dingy-yellow landscape would seem to tilt a little. If unshielded human eyes could have endured the rays of Nu Puppis, Niflheim’s primary, the whole scene would have appeared a vivid Saint Patrick’s Day green, the effect of the blue-predominant light on the yellow atmosphere. The outside ’visor-pickup, however, was fitted with filters which blocked out the gamma-rays and X-rays and most of the ultraviolet-rays, and added the longer light-waves of red and orange which were absent, so that things looked much as they would have under the light of a G0-type star like Sol. The air was faintly yellow, the sky was yellow with a greenish cast, and the clouds were green-gray.

A thousand feet below, the local equivalent of a forest grew, the trees, topped with huge ragged leaves, looking like hundred-foot stalks of celery. There would be animal life down there, too—little round things, four inches across, like eight-legged crabs, gnawing at the vegetation, and bigger things, two feet long, with articulated shell-armor and sixteen legs, which fed on the smaller herbivores. Beyond, in the middleground, was open grassland, if one could so call a mat of wormlike colorless or pastel-tinted sprouts, and a river meandered through it. On the skyline, fifty miles away, was a range of low dunes and hills, none more than a thousand feet high.

No human had ever set foot on the surface, or breathed the air, of Niflheim. To have done so would have been instant death; the air was a mixture of free fluorine and fluoride gasses, the soil was metallic fluorides, damp with acid rains, and the river was pure hydrofluoric acid. Even the ordinary spacesuit would have been no protection; the glass and rubber and plastic would have disintegrated in a matter of minutes. People came to Niflheim, and worked the mines and uranium refineries and chemical plants, but they did so inside power-driven and contragravity-lifted armor, and they lived on artificial satellites two thousand miles off-planet. This vehicle, for instance, was built and protected as no spaceship ever had to be, completely insulated and entered only through a triple airlock—an outer lock, which would be evacuated outward after it was closed, a middle lock kept evacuated at all times, and an inner lock, evacuated into the interior of the vehicle before the middle lock could be opened. Niflheim was worse than airless, much worse.

The chief engineer sat at his controls, making the minor lateral adjustments in the vehicle’s position which were not possible to the automatic controls. One of the radiomen was receiving from the orbital base; the other was saying, over and over, in an exasperatedly patient voice: “Dr. Murillo. Dr. Murillo. Please come in, Dr. Murillo.” At his own panel of instruments, a small man with grizzled black hair around a bald crown, and a grizzled beard, chewed nervously at the stump of a dead cigar and listened intently to what was—or for what wasn’t—coming in to his headset receiver. A couple of assistants checked dials and refreshed their memories from notebooks and peered anxiously into the big screen. A large, plump-faced, young man in soiled khaki shirt and shorts, with extremely hairy legs, was doodling on his notepad and eating candy out of a bag. And a black-haired girl in a suit of coveralls three sizes too big for her, and, apparently, not much of anything else, lounged with one knee hooked over her chair-arm, staring into the screen at the distant horizon.

“Dr. Murillo. Dr. Mur—” The radioman broke off in mid-syllable and listened for a moment. “I hear you, doctor, go ahead.” Then, a moment later “What’s your position, now, doctor?”

“I can see them,” the girl said, lifting a hand in front of her. “At two o’clock, about one of my hand’s-breadths above the horizon.”

The man with the grizzled beard put his face into the fur around the eyepiece of the telescopic-’visor and twisted a dial. “You have good eyes, Miss Quinton,” he complimented. “Only four personal armors; Ahmed, ask him where the fifth is.”

“We only see four of your personal armors,” the radioman said. “Who’s missing, and why?” He waited for a moment, then lowered the hand-phone and turned. “The fifth one’s inside the handling-machine. One of the Ullerans. Gorkrink.”

The larger of the specks that had appeared on the horizon resolved itself into a handling-machine, a thing like an oversized contragravity-tank, with a bulldozer-blade, a stubby derrick-boom instead of a gun, and jointed, claw-tipped arms to the sides. The smaller dots grew into personal armor—egg-shaped things that sprouted arms and grab-hooks and pushers in all directions. The man with the grizzled beard began talking rapidly into his hand-phone, then hung it up. There was a series of bumps, and the armor-tender, weightless on contragravity, shook as the handling-machine came aboard.

“You ever see any nuclear bombing, Miss Quinton?” the young man with the hairy legs asked, offering her his candy bag.

“Only by telecast, back Sol-side,” she replied, helping herself. “Test-shots at the Federation Navy proving-ground on Mars. I never even heard of nuclear bombs being used for mining till I came here, though.”

“Well, if this turns out as well as the other job, three months ago, it’ll be something to see,” he promised. “These volcanoes have been dormant for, oh, maybe as long as a thousand years; there ought to be a pretty good head of gas down there. And the magma’ll be thick, viscous stuff, like basalt on Terra. Of course, this won’t be anything like basalt in composition—it’ll be intensely compressed metallic fluorides, with a very high metal-content. The volcanoes we shot three months ago yielded a fine flow of lava with all sorts of metals—nickel, beryllium, vanadium, chromium, indium, as well as copper and iron.”

“What sort of gas were you speaking about?” she asked.

“Hydrogen. That’s what’s going to make the fireworks; it combines explosively with fluorine. The hydrogen-fluorine combination is what passes for combustion here; the result is hydrofluoric acid, the local equivalent of water. See, the metallic core of this planet is covered, much less thickly than that of Terra, with fluoride rock—fluorspar, and that sort of thing. There’s nothing like granite here, for instance. That’s why those big dunes, out there, are the best Niflheim has in the way of mountains. The subsurface hydrogen is produced when the acid filters down through the rock, combines with pure metals underneath.”

“Dr. Murillo’s inside, now,” the radioman said. “Just came out of the inner airlock. He’ll be up as soon as he gets out of his pressure-suit.”

“As soon as he gets here, I’ll touch it off,” the bearded man said. “Everything set, de Jong?”

“Everything ready, Dr. Gomes,” one of his assistants assured him.

The door at the rear of the control-cabin opened, and Juan Murillo, the seismologist, entered, followed by an assistant. Murillo was a big man, copper-skinned, barrel-chested; he looked like a third—or fourth—generation Martian, of Andes Indian ancestry. He came forward and stood behind Gomes’ chair, looking down at the instruments. His assistant stopped at the door. This assistant was not human. He was a biped, vaguely humanoid, but he had four arms and a face like a lizard’s, and, except for some equipment on a belt, he was entirely naked.

He spoke rapidly to Murillo, in a squeaking jabber. Murillo turned.