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WHERE DID EVERYBODY GO? - John Wood Campbell

The data that Mariner II signaled back as it passed Venus last December has been released only gradually - and turns out to be largely confirmation of the completely upsetting fact that Venus has a surface temperature of some 6oo° F to 8oo°F. It's upsetting, because it shatters nearly all our conceptions of the nature of the planets - and of the probabilities of life on other worlds.
Combined with the recent determination of the nature of Mars' reddish color, and the nature of those polar caps, the Solar System has suddenly become a mighty lonely-looking place. Mars' reddish color, it now appears, is due to the familiar red-brown nitric oxide gas in its thin atmosphere - and the polar caps are solid masses of the white solid form of nitric oxide. It's unnecessary to look for water on Mars, now; if there is any free liquid, the brooks and lakes would be what is now familiarly designated as RFNA - fine for rocket fuels, but Red Fuming Nitric Acid isn't for drinking.
But science fiction has lost more than its Venus colony - at 8oo°F - and its Mars colony. We just lost the chance for intelligent aliens circling other stars. Because the facts we've now learned force a revision of our most basic conception of What Planets Are Like.
We've been deluded by an especially tricky type of reasoning-trap, that is usually almost impossible to detect until after you've been suckered by it. In this case, it goes "I know what planets are like; I live on one". The stinker in that happens to be that our knowledge relates to a so-far-as-we-know absolutely unique planet, and one that our knowledge to date indicates must be at least extremely unusual in the Universe.
You see, what we've overlooked is the fact that we live on one component of a binary planet.
What are the chances of another binary planet like the Earth-Moon system circling another adequately long-lived star at a distance producing a suitable temperature on a clear-atmosphere planet?
Venus has long been described as Earth's twin; with a diameter of 7,500 miles to Earth's 8,000, surface gravity eighty-five per cent of Earth's, at about two thirds Earth's distance from the Sun - it sure looked as though Venus would be very similar to Earth.
The radio astronomers, several years ago, began getting data on the surface conditions on Venus - and the answers were so unbelievable that they were accepted only with the greatest reluctance. That Venus, Earth's twin, should have a temperature that would melt lead was incredible. The fantastically high temperature readings were ascribed to some anomalous radio frequency emission from the planet.
Optical astronomers couldn't penetrate Venus' cloud layer well enough to get even so much as data on the rate of the planet's rotation, let alone get any useful surface detail. The spectroscope, ordinarily able to answer many questions that direct observation couldn't, failed completely on Venus; whatever the planet's rotation rate, it was so slow that the spectroscope couldn't detect it. Whatever the atmosphere of Venus contained, it wasn't anything we could be sure of. Carbon dioxide... probably. Water... no readable indications. The planet of mystery...
Radio astronomers, working at enormously longer wavelengths than those used by optical astronomers, were able to get signals from Venus that most probably did emanate from the actual solid surface, not from the clouds above. But their data came up with insane answers! Earth, if it were at Venus' distance, should have an average temperature of 150°F. That Venus could have a temperature so enormously higher...
Repeated checks gave the same answers. And tests for radio frequency spectrum responses due to water vapor - it has spectrum lines in the microwave region, as well as in the "optical" range - gave negative answers.
We've known about the "greenhouse effect" - the ability of an atmosphere to trap solar energy by allowing short-wave visible energy in, but blocking the re-radiation of longer wavelength heat - for a long time. But never in the degree Venus now turns out to have! Venus has a "greenhouse" that could be used for a home pottery kiln, practically - certainly not as either a greenhouse or even a home bake-oven!
The clouds appear to be a solid fifty to seventy-five mile thick layer of the most vicious kind of industrial smog-type components; complex hydrocarbons and assorted mineral acid vapors.
We on Earth here tend to think of nitrogen as an "inert ingredient" in an atmosphere. Completely wrong! Earth now appears to be the only planet in the Solar System on which nitrogen is free in the atmosphere! On the giant planets - Jupiter, Saturn and the rest - nitrogen is linked with hydrogen in ammonia. And to form great mountains of a solid metallic substance that doesn't exist as free metal on Earth - ammonium metal, NH4 (under the extreme pressures in the giant planets' atmospheres, NH3 + H2 is less stable than the solid metallic form, NH4).
On Mars, nitrogen is linked up with oxygen in nitric oxide. On Venus, seemingly, nitric oxides are present also (and, incidentally, in the Sun's atmosphere, nitrogen is one of the few elements that can remain in combination even at solar temperatures - that everybody-knows-its-inert element combines with carbon to form cyanogen - CN - can be detected in the solar spectrum).
Down on the surface of Venus, under the tens of miles of smog, the conditions closely approximate the conditions at the bottoms of Earth's deepest seas in several important respects. The darkness is absolute; there is no light whatever. There is moreover, neither weather nor climate; the immensely thick insulating blanket prevents all temperature fluctuations from day to day - even with Venus weeks-long day - or from year to year. Down there, there is only an unending, searing, black calm.
Earth has jet streams in its atmosphere - stratosphere, to be accurate - which roar around the planet at hundreds of miles an hour, constituting a major heat-distribution mechanism. Venus has jet streams, too - but with the immense depth of atmosphere, and the enormous heat differentials resulting from the very slow rotation, Venus' jet streams apparently achieve wind velocities of thousands of miles an hour.
Those stupendous winds high in Venus' atmosphere do not, however, mean that the surface layers of that atmosphere are disturbed; Earth's jet stream are only a few miles above Earth's surface, yet immediately under a 250-mile-an-hour jet stream there may be the dead calm of a hot summer day.
Venus' atmosphere supports completely opaque clouds some sixty miles above the planet's surface, Mariner II reported. At a fifty mile altitude above Earth, by current definition, a man is legally in space. And certainly it's far beyond aerodynamic flight support!
To be able to support opaque clouds at sixty miles, Venus must have many, many times Earth's atmosphere. If it matches Earth's cloud-layer density at sixty miles, remember that Earth's atmospheric density doubles, approximately, every five miles you go down. If Venus' doubles for each six miles, then Venus must have several hundred times as much atmosphere as Earth.
And this is Earth's "twin planet"?

All the work the geophysicists, cosmologists and astrophysicists have done during the past century must now be massively reevaluated. In computing the way a planet gains or loses atmosphere, they have, naturally, checked their computations against the facts concerning the available planet - Earth.
It turns out they've been checking their figures against a planetary freak. Venus, nearly exactly Earth's size, retained scores of times as much atmospheric gas - and if anything, Venus is smaller, and we now know it's also very much hotter. Earth's atmosphere should be at least two whole orders of magnitude greater than it is!
Mercury, of course, has no atmosphere; as close to the Sun as it is, and as small as it is - almost exactly three thousand miles in diameter - it couldn't retain gases.
Of the other eight planets, only three have transparent atmospheres - Earth, Mars and Neptune (Pluto is unknown, but almost certainly clear). Neptune's is clear because the planet's temperature is so low that nothing but hydrogen, helium and neon remain gaseous; there's nothing to make a condensable vapor at those temperatures. Mars' is clear because of its extreme thinness.
And Earth's is clear because of its extreme thinness.
Every other major planet capable of retaining atmosphere is a clouded-atmosphere, or opaque-atmosphere planet. Earth's a freak.
In the past, we've guesstimated the probable surface temperature of other planets by supposing Earth were in the orbit of the other planet. In Venus' orbit, Earth would have a temperature of about 150°F. In Mars' orbit, Earth would have a temperature about -40°F. In Jupiter's orbit...
And now that we know Earth is in fact a freak, how about trying Venus as the sample - what of Venus-type opaque-atmosphere planets at those different distances? That would make much more sense, since, with the exception of Mars, the others we're interested in are opaque-atmosphere worlds!
On the basis of Venus' actual surface temperature, Jupiter and Saturn both may have a liquid-water surface temperature.
Recently I had an editorial here on the question of which stars might be expected to have planets capable of supporting life.
All of those remarks now have to be re-evaluated - because it now appears that planets as close to Sol-type stars as Earth and, probably, Mars will normally have surface temperatures well above 212°F. Earth would have a surface temperature - if it weren't a freak - above the 372°C. temperature at which water becomes a "permanent gas" i. e., no amount of pressure can liquify it. The life-temperatures zone around a star, in other words, starts for normal, opaque-atmosphere planets, much farther out than Earth, and extends to the region where even an opaque-atmosphere heat-trap can't keep the planet warm. There is, however, one slight difficulty.
Life evolved on Earth, and we've had a lot of discussion and studies to show that life would, by the nature of things, tend to evolve on any planet having the necessary temperature range.
Sorry... try again! On any freak binary planet having a clear atmosphere, and also having gravity enough to retain light gases such as the hydrogen necessary for making water.
One of the strange anomalies of life in Earth's oceans is that the Antarctic Sea is by far the most densely populated body of water on Earth. It certainly seems improbable that life should congregate most thickly in that icy cold zone of long, bitter nights.
The reason depends on the fact that life must have three absolute essentials; light, for energy input; fluid for chemical transport medium; and minerals to be transported and interacted.
The ocean deeps have the greatest concentration of minerals; there, there are the minerals needed for abundant life... but there is no light, so none of the photosynthetic life forms can get the energy to live, and only a very few scavenger forms live on detritus raining down from the upper levels.
In the tropical waters, where light is brilliantly and regularly available, and the water is warm, which tends to speed biological processes... there is so acute a shortage of minerals - particularly phosphorus - that the microscopic plant forms on which the whole life chain of the ocean depends cannot grow.
But in the Antarctic Sea, the deep waters from the ocean floor, heavily laced with minerals, are forced up to the ocean surface - into the zone where light, water, and minerals can be found simultaneously. The sea swarms with life!
An opaque-atmosphere planet presents a not-entirely-dissimilar problem. At the surface of the planet are minerals; at the top of the atmosphere is light energy. But is there any way for the two ever to get together with a usable fluid?

In the case of Venus, we have evidence that there is no water, even in the deep layers of the atmosphere, for even microwave radio astronomy hasn't detected it. But assume a Venus-like planet that did have water vapor.
Now the top cloud layers of Venus have a temperature around sixty degrees below zero F.; the surface has a temperature around eight hundred degrees above zero; there must be a region somewhere in between where water can exist as a liquid.
However, the problem life would encounter is this: at the lighted surface of an opaque-atmosphere planet, the temperature is very low. Ammonia might serve as a life fluid at that level. But the deep levels are much too hot for the cold-level fluid to exist! No one substance would be usable as a fluid both at the lighted top zone, and at the mineral-rich bottom!
There is, of course, always some dust in a planetary atmosphere. How about dust being carried up from the mineralized surface levels to a fluid level far enough up for photosynthesis?
Up through anything from fifty to five thousand miles of opaque atmosphere, you mean? Remember, the bottom of an opaque atmosphere is, by the nature of the processes, calm. Mighty little dust-stirring there, where the dust exists to be stirred. Venus' upper lighted levels may well get more dust-input from micrometeorites falling from space than from stragglers who climbed fifty miles against gravity to reach sunlight.
In Jupiter's case, the outer layers are definitely known to be ammonia clouds, laced with metallic sodium. But the opaque-atmosphere model suggests that Jupiter's surface temperatures must be in the liquid-water range, or perhaps even higher (if those opaque atmospheres trap solar heat that effectively, they must also block the escape of radioactive heat to a fantastic degree. And the quantity of potassium-40 in the mass of Jupiter would generate quite a little heat!).
Jupiter would then be a case of a planet whereon only an ammonia-fluid life form could exist in the photo-active levels - and only a water-fluid life form could exist in the surface layers! And inasmuch as there is strong evidence for free metallic sodium and metallic ammonium in Jupiter's clouds, neither of which can coexist with H2O, we can drop that problem.
So... can an opaque-atmosphere planet permit the evolution of living forms?
Evidently life-as-we-know it would be unable to find the three necessities in any place simultaneously.
Now the mass of matter in the Universe is practically pure hydrogen, with some helium, and traces of contamination by heavier elements. Planets, because of their small gravitational fields, lose practically all the gases, and retain only the trace contaminants; Jupiter and Saturn have made out somewhat better, but even they must have lost something like ninety-eight per cent of the original gaseous mass from which their remaining matter was gathered.
The most abundant elements seem to be - after hydrogen and helium, of course - the lighter elements, which are the ones first manufactured in stellar cores, and iron, which is the lowest-energy nucleus and the true ash of stellar thermonuclear reactions (energy is released in building all elements up to Fe-56; energy is consumed in building all elements above Fe-56. U-235 fissions and yields energy because it is far above the Fe-56 least-energy-nucleus structure, and breaking down toward the lighter elements yields energy).
There are three elements that can't exist in stellar thermonuclear cores - lithium, beryllium and boron have no isotopes that can maintain existence in a thermonuclear core. Deuterium - "heavy hydrogen" - can't remain either. These four react more rapidly, at a lower temperature, than does hydrogen - so they go first and fastest.
The element next after boron is carbon - and carbon, oxygen and nitrogen are the three elements taking part in the "solar Phoenix" reaction, important thermonuclear processes in stellar mechanics. After oxygen comes fluorine - which has a single isotope, F-19, and while it's stable, it doesn't stand up well in a thermonuclear core. Then we get to neon, sodium, magnesium and aluminum.
In the raw material of planets, hydrogen, carbon, nitrogen and oxygen play crucial roles. Hydrogen and oxygen are the most abundant - so far as Solar System indications go! - with nitrogen and carbon less so. Oxygen can combine to form oxides of the rocky types with silicon, magnesium, and aluminum; in addition, hydrogen oxide - water - is, of course, common.
Nitrogen can combine either with oxygen or hydrogen - but at planetary temperatures, neither nitrides of the metals nor the cyanogens seem to be favored.
In Earth's atmosphere, nitric oxides are constantly being formed by solar electron bombardment, UV activity, and by electric sparks - lightning - in the atmosphere. And the biological activities of organisms are greedily consuming every molecule of the combined nitrogen they can get hold of. If if weren't for the biological activities, nitrogen oxides would accumulate in Earth's atmosphere.
In Jupiter's atmosphere, the immense excess of hydrogen swept all the oxygen out of the atmosphere; there, the enormous pressure makes the reaction N2 + 3H2 = 2NH3 strongly favored.
On Earth, the free oxygen in the atmosphere tends to favor strongly the production of carbon dioxide; on Jupiter, the hydrogen excess favors the formation of carbon tetrahydride-methane, CH4.
In each case, the atmospheres of the planets grow almost solely" from the interactions of the four lightest thermonuclear-stable elements, hydrogen, carbon, nitrogen and oxygen.
The thermonuclear probabilities make it very unlikely that any other gases could be important on planets elsewhere in the Universe. Fluorine, the only other first row of the periodic table element, is very low in cosmic abundance (the helium nucleus of mass number 4 seems to be the stable unit of construction for the fighter elements. Oxygen-16 is four times He-4; carbon-12 is three times, and neon-20 is five times. Fluorine-19 is not favored. Nitrogen-14, halfway between C-12 and O-16 and one of the major steps in the "solar Phoenix reaction" is favored).
Venus' smog-type opaque atmosphere appears to be made up of what might be expected from those interactions. Evidently the planet - somewhat lighter than Earth and nearer the Sun's heat and ionization - lost nearly all its hydrogen while forming. Most of its oxygen combined with rock-forming elements. The remaining hydrogen, nitrogen, carbon, and oxygen assorted themselves into a system partway between the ammonia-methane system of Jupiter, and the nitric-oxide system of the still-lighter planet Mars.
Start with the hydrocarbon-ammonia atmosphere of Jupiter, and reduce the hydrogen content while leaving the other gases fairly constant. The ammonia will go over to nitrogen oxides, the carbon will go from methane, CH4, to CO and CO2, as oxygen becomes relatively dominant. The interaction of the resulting mixture of nitrogen and carbon oxides with methane will lead to the production of higher, more complex hydrocarbons and hydrocarbon derivatives. There will be complex aldehydes, alcohols and organic acids, with assorted attached nitro and amine groups.
These reactions will be driven by the high-energy radiation of the Sun - the ultraviolet quanta, impacting electrons and protons, soft X rays, et cetera, reacting on the uppermost layers of the planet's atmosphere.
Our own atmosphere shows traces of nitric oxides from solar bombardment at the uppermost levels, for instance.
Now Venus has so high a surface temperature that there is no usable fluid at the surface. But - suppose Venus had a bit more water, and were moved out to Jupiter's distance. We would then have a curious possibility for a totally new kind of life-system.
That process of radiation-excited reactions between the atmospheric hydrocarbons and nitric oxides will tend to produce fairly complex organic compounds. Radiation-produced amines and radiation-induced acids will combine on contact to form larger and more complex molecules - which will tend to sift downward under gravity.
These complex organic compounds can serve as food for living cells that operate on a fermentation basis! It would be possible, in other words, for a life-system to evolve on an opaque-atmosphere planet, with no equivalent of plant forms! The planet's atmosphere itself would serve to fix radiant energy in the form of organic compounds, and the slow trickle of resulting compounds downward to the fluid-mineral supply at the surface would make life possible in total absence of light energy input.
The resultant surface life would all be "animal" in the sense of being energy-releasers rather than energy-fixing organisms. Like the living forms at the bottoms of our ocean deeps, the whole system would be dependent on the thin rain of organic detritus from far above. Living in absolute darkness, on very thin rations, they would, in effect, be smog-eating organisms. Their output of carbon dioxide, nitrogen and water would return to the atmosphere, filtering slowly up through the vast blanket of opaque smog, to the reactivation levels where sunlight could act on it.
Life-as-we-know it, with plants and animals in a balanced symbiosis, would not be possible. And the purely accidental radiation-activation of atmospheric components suggested would be immeasurably less efficient than the photosynthetic activities of plants. But still, a thin population of living things could evolve - a population as thin as, or thinner than, that in our ocean deeps.
And this could happen on what we must now recognize as the normal type of planet - the opaque-atmosphere planet.
But... could intelligent organisms evolve? Say on Jupiter. Thin as the population might be, with the stupendous size of the planet, there would still be possibilities of millions of entities.
The work on Project Ozma, seeking to contact possible other intelligent races on nearby other-star planets, assumed that any race as intelligent as the human race would, like us, develop and use radio-frequency communication.
We now have serious reason to question that.
On an opaque-atmosphere world, an intelligent race would never see sun, stars or planets; they would have neither weather nor climate.
Human science started with astrology - the science of predicting coming events - seasons - by the stars. It led to the necessity of measurement of angles. Quantitative-measurement is the basis of all our sciences - and they developed largely from astrology and surveying, which developed from the angle-measurement work and geometrical studies astrology induced. Astronomy offers no immediate pragmatic rewards such that a subsistence-level culture would support an observatory and an observer; astrology did. It was most decidedly important to learn how to predict the change of seasons. And then surveying became possible as a sort of unexpected bonus. And then...
The dark-world intelligences would not have that stimulus.
On Earth, the Eastern philosophers have tended far more toward the non-quantitative, purely-qualitative fields of subjective phenomena.
If, even on Earth, where there is powerful direct stimulus toward the quantitative measurement sciences, a major portion of the human philosophers have tended toward the qualitative-subjective - what would the dark-worlders do?
Radio techniques are an outgrowth of optics, actually - an extension of electromagnetic theory of light into lower frequencies was the original motivation of Hertz's experiments.
There's evidence that quite different types of possibilities exist, beyond the domain of science we know. Clairvoyants have existed; ESP does occur. Telekinesis has happened.
Suppose that there are planets of Tau Ceti, and Project Ozma's beamed radio signals are quite futile - just as futile as the Tau Cetans beamed clairvoyance-band transmissions. Never having worked with the electromagnetic spectrum, they don't have the radio-optical gadget we know as TV; they use an equally sophisticated gadget that is a clairvoyance machine. And they know that, obviously, any equally intelligent race anywhere must surely develop clairvoyance transmission equipment.
Would we recognize their civilization if we saw it? Or would they recognize ours if they encountered it?
They've been saying those "flying saucers" are purely illusions. Well - maybe they are. Purely subjective phenomena. Remote clairvoyance pickups, purely subjective devices, transmitted from Jupiter or Tau Ceti VI or...?
But one thing seems rather starkly clear from the data we now have.
The Universe may be full of planets - millions and millions of them. Nice, normal planets... like Venus or Mercury or Jupiter.
But Man is going to have a problem. Terra-type planets are binary planets. It takes the contending gravitational fields of two condensing nuclei to strip the gases away from a major planetary body and leave a medium-large planet with a freakishly clear atmosphere.
And we're going to be pretty lonely in the Universe as a result.
Where is everybody?
Hidden under an impenetrable blanket of viciously corrosive smog... if they exist at all.

July 1963