Living on Other Planets

Imagine you opened tomorrow's newspaper to find this headline: EARTH TO BE DESTROYED IN THREE HUNDRED YEARS. The cause might be a collision with another body, an internal explosion, or the Moon falling from its orbit. Not likely, perhaps—but let us use this as an exercise for the imagination.

How would humanity take such news? At first, people would be thrilled—what drama! But the event would seem too remote to take seriously. Most would simply eat, drink, and be merry, pushing the problem to future generations.

Gradually, however, realization would dawn. Three centuries is only ten or twelve generations. Some now living might have grandchildren who would see the end.

Some, at least, would insist that humanity must continue. "The great adventure must go on!" they would say. Humanity is only a million years old. Its possible future spans thousands of millions of years—time enough to become something far finer than we are now.

Consider the trajectory: from worm to fish to reptile to mammal to monkey to man. Why should the story end here? Might we not become superman, or something beyond even that?

If so, there is a sacred duty to preserve humanity. We must find another world and send at least a few men and women there to continue the species. The rest of us must accept death, but the adventure would continue.

Gradually, I think, this view would spread. A great project would emerge.

How would we set about such a task? Four steps:

First, intensive study of the planets with telescopes and whatever other instruments we could devise. Second, invention of "ether ships"—vessels capable of carrying humans through space. Third, exploration of the possible destination planets to choose the best. Fourth, preparation—of both the new world for humanity, and humanity for its new world.

Is space travel impossible? Not if we really wanted it. The rocket principle would serve—"rocket to the moon," as they say. We would need a huge ship, powered perhaps by explosive mixtures or, more likely, by subatomic energy.

Once beyond Earth's atmosphere, no further push is needed except for steering and stopping. The ship would coast through the void. But there would be dangers: meteors might puncture the hull, and the ship might become incandescent when approaching the Sun.

The problems of air, food, and water are not insurmountable: compressed or liquid oxygen, recycled water, stored and grown food. The voyage would take months or years. Elaborate heating and cooling systems would be required—warmth when far from the Sun, cooling when near it. All difficult—but not impossible.

Before we succeeded, there would be many experiments—and tragic failures. Ships might break apart under the stresses of launch. They might lose their air through tiny punctures. They might collide with debris, or fail to return. Crews might freeze in the outer darkness or cook in solar proximity. Steering might fail, sending ships hurtling into the void forever.

Each failure would teach us something. Each lost crew would be martyrs to the cause of human survival. Eventually, we would learn.

Imagine that first successful voyage! The start with a tremendous bump as the rockets ignite. The horizon contracts—an aeroplane view, then something no aeroplane passenger has ever seen. The Earth becomes circular, then gibbous like the Moon, then a crescent as we pass it.

The sky darkens—less and less air to scatter the light. Stars appear even when the Sun is visible. The Earth shrinks behind us. Gravity weakens until we float freely in the cabin, perhaps wearing magnetic boots for artificial gravity.

The first trip might only approach the Moon—circumnavigate it, perhaps, or even land. But we could not go outside: no air. The Moon would be a trial run for longer voyages.

The Moon is useless as a home, save perhaps for mining metals and minerals. It has no air to breathe, no water—only rock and mountains and crater walls.

Why no air? Because air molecules are always jumping about very fast. On a small world like the Moon, the outside layer of molecules jumps too fast for gravity to hold them. They escape into space—like the fizz escaping from soda water. Earth is massive enough to hold its air, but no small world can.

Could we give the Moon an atmosphere? Tranship air from Earth? It seems hopeless. And even if we could, it would trickle away in a few thousand years. The Moon offers no permanent home.

Mercury is useless. It is too small to hold an atmosphere. Like our Moon, it keeps one face always toward the Sun. On the hot side, lead would melt—temperatures hot enough to destroy any imaginable structure. On the cold side, extreme frost.

Perhaps on the "limb"—the twilight zone between day and night—conditions might be tolerable? But it would be a very narrow strip of habitability.

Worse: ether ships approaching Mercury would melt en route! We might refrigerate them for exploration, but Mercury offers no promise as a home.

Venus is roughly as large as Earth—promising! It has a dense atmosphere shrouded in cloud. But there is no free oxygen to breathe, so at present Venus is useless to us.

An ether ship would have a hot voyage approaching Venus. It would sink through the cloud layer. What surface lies beneath? Sea? Islands? We do not know.

Why no oxygen on Venus? Because oxygen is "too friendly"—it easily combines with other elements. Without something constantly producing it, you would not expect to find free oxygen anywhere.

Then why is there oxygen on Earth? Because plants keep pouring it into the air—faster than it can combine with other elements, faster than animals breathe it. Therefore: no plants on Venus, and no animals. A dead world—or possibly some other sort of life that does not depend on oxygen.

But Venus might be prepared! The process would take generations:

First, exploration to find suitable sites for settlement. Second, the building of electrolysis stations to split water and release oxygen into the atmosphere. Third, introducing plants from Earth—specially bred to survive Venusian conditions—which would continue producing oxygen. Fourth, gradually acclimatizing human beings to the heat and other conditions. Fifth, colonization—though most of humanity would have to be left behind to die.

The food problem would be severe: no native food, and terrestrial vegetation would take too long to establish. But there is a wealth of sunlight above the clouds—perhaps we could manufacture synthetic food directly from solar energy.

What would Venusian settlers find? Perhaps the surface is all ocean—or scattered islands. There would certainly be storms, violent ones, given Venus's proximity to the Sun. A bright white sky, eternally overcast.

And might there be native life? Life of some unfamiliar kind that does not need oxygen? If so, what would be our relationship to it?

Generations would be born on Venus who had never known Earth. What kind of society would they create? Would they repeat our mistakes—class war, national war? Or might they make a new start, a genuinely new civilization? Venus might become a wealthy world, rich in solar energy.

Mars is much smaller than Earth. It has an atmosphere, but not much—less than at the top of Everest. There is oxygen, but only about 15% of what we have on Earth. Water vapor exists, but very little.

Mars is far from the Sun and very cold. On the equator at noon, it would be like a "cold bright day" in our winter. In Martian winter, colder than our Arctic.

We could not live there in the open—we would suffocate and freeze. But might we acclimatize babies born there, each generation adapting a bit more? The policy might be: establish an ether-ship station as an anchorage, then gradually produce a native population over many generations.

What would explorers find on Mars? Mostly desert—reddish sand or rock, the rusty color we see through telescopes. But probably also large districts of vegetation: greenish in Martian spring, brown in winter. What kind of vegetation? Perhaps something feathery, adapted to the thin air?

There are polar caps that grow and shrink with the seasons—the south cap vanishes entirely in summer. Are they water ice or frozen carbon dioxide? The very existence of vegetation proves there is some oxygen being produced—confirming that plant life exists on Mars.

What of the famous "canals" of Mars—those straightish lines that seem to connect the green regions? The astronomer Lowell claimed they were built by intelligent beings to irrigate the desert. But this is all very doubtful—the lines may be optical illusions or natural features.

Still, if there are intelligent Martians, our explorers might be resisted. War! We have no idea what Martians would be like—very different from us, certainly. Think of H.G. Wells's terrifying Martians in The War of the Worlds. Our explorers might be destroyed.

Even apart from possible resistance, settlers would face many problems:

Food: Could we eat Martian vegetables? They might poison us—their biochemistry would be quite different from Earth's. Cultivating Earth vegetables would be difficult in the thin air and weak sunlight.

Energy: No coal or oil—those are products of Earth's ancient forests. We might burn Martian vegetation, but there would be no water power (no rivers to speak of) and little wind power in the thin atmosphere.

Transportation: No seas to navigate, so no ships.

Mars would be a poverty-stricken world. Could it even support much life? Water shortage, air shortage, biochemical difficulties, and above all light shortage—so far from the Sun.

There would be compensations. Flying would be difficult in one way—the air is too thin to support conventional aircraft—but easy in another, because gravity is slight. Perhaps rocket-powered flight, or gliding on huge wings.

Athletics would be wonderfully easy! With Mars's weak gravity, we could jump like grasshoppers. A running leap might carry you twenty feet into the air. What sports they might invent!

The asteroids are too small—ranging from ten to five hundred miles across. On some, you might accidentally jump off into space! No atmosphere, too cold.

Jupiter is enormous, with crushing gravity—we could hardly stand up. It has an atmosphere with dense clouds, but whether there is oxygen, we do not know. And it is terribly cold; the Sun appears as a mere bright star. If natives exist, they must be small and sluggish under that terrible gravity.

Saturn is even worse—similar problems plus those magnificent but useless rings. Uranus and Neptune are colder still—from Neptune, the Sun would look like a bright arc lamp rather than the blazing disc we know. And Pluto, at the edge of the solar system, is beyond consideration.

What is the upshot of all this? We might colonize Venus and Mars—but the colonists would have to become very different types of beings, adapted over generations to conditions utterly unlike Earth's. They might hardly recognize their Earthly ancestors.

At any rate, we may explore these worlds someday. The great adventure is not impossible.

The old views were extreme: either life is only possible on Earth, or the universe teems with life on every world. The truth is probably between.

Planets are rare. Stars are common—as numerous as sand covering the British Isles fifteen feet deep. But planets form only occasionally, perhaps one born every 200,000 years in our galaxy. There may be a million or so—but few suited to life.

Life's prerequisites: the right temperature range, a flow of energy (from a nearby sun), diversity of circumstances to drive evolution. These conditions are not common.

But perhaps we think too narrowly. J.B.S. Haldane has speculated about stellar life—beings living in the interiors of stars, where the temperature is millions of degrees. Could there be a fiery brain at the heart of the Sun? Creatures like the legendary salamanders that live in fire?

And what of the nebulae—those vast clouds of gas between the stars? Might some form of life exist there, spread across light-years?

The cosmos is stranger than we can imagine. We are only beginning to ask the right questions.

To return to our scenario: a disunited world, absorbed in war and trade, could never accomplish such a project as interplanetary colonization. All the resources of humanity would be needed. We must unite.

And here is the great irony: the project of saving humanity from cosmic catastrophe might itself be what finally unites humanity. It would give life a new meaning beyond petty rivalries. It would demand the best from everyone. It would create, perhaps for the first time, a civilization actually worthy of survival.

The threat of extinction might be our salvation—not from extinction itself, but from the spiritual poverty that makes our present existence hardly worth saving.