Science: Life Beyond Earth?

Harold Spencer Jones, M.A., Sc.D., F.R.S., is England’s Astronomer Royal. A hardheaded, straight-thinking scientist, who refers to writings of Eddington and Jeans as “romance,” he is, ex officio, director of Greenwich Observatory and responsible for Greenwich time’s astronomical integrity.* The question he has heard most often in his 50-year career is: Does life exist on other worlds? Astronomer Jones set out to assemble the evidence in the case, published his conclusions last week in Life on Other Worlds (Macmillan; $3).

The same 92 standard elements from some of which earth’s life is formed appear to be universal. No one, even with the most powerful microscope, has ever seen an atom. But modern astronomy, by splitting starlight in spectroscopes where atoms leave their signatures in parallel lines, has identified chemical elements in stars trillions and quadrillions of miles away. There is no reason to suppose that life cannot exist in worlds beyond earth for lack of suitable materials.

But in living organisms the elements are grouped in complex molecules. Living structures are broken up by even mild heat. They cannot stand temperatures of 150° F. and over. The sun’s surface temperature is about 10,000°, and no known star is cooler than 2,000 or 3,000°. Thus the stars are instantly ruled out as possible abodes of life. That leaves the planets.

Planetary life, whatever its forms, must be built of cells or some other organic units comparable to the cells of earth’s plants and animals. Such cells must have access to water, as a medium of nourishment and energy exchange, and to oxygen or carbon dioxide for metabolism. An atmosphere would also be desirable, 1) as a storehouse of oxygen and carbon dioxide; 2) as a shield against the ultraviolet radiation of the parent sun; 3) as a muffler against sharp day & night temperature changes. Any conceivable kind of living cell would be killed or paralyzed by extreme cold.

The temperature of Jupiter is about 220° below zero F., and the outer planets—Saturn, Uranus, Neptune, Pluto—are even colder, which eliminates them as harborers of life. Moreover the atmospheres of the big planets contain great quantities of ammonia and methane, which are poisonous to earthly organisms. These substances are rich in hydrogen, lightest of gases and hence the most likely to escape from a planet’s gravitational pull. The big planets are massive enough still to retain most of their original hydrogen, hence the ammonia and methane. The young earth locked up some useful hydrogen in water vapor and fortunately lost most of the rest.

There can be no life on Mercury or on the earth’s moon, says Astronomer Jones. These bodies are too small to have held their atmospheres. The telescope and spectroscope both clearly show the moon to be a dead world, without air or water. Having no atmospheric muffler, the moon swings through a temperature change of several hundred degrees between the lunar day and night. Mercury, innermost of the planets, keeps one face turned always toward the sun. That side is extremely hot—about 750°—and the perpetually dark side must be correspondingly cold.

Venus is the nearest of the major planets to Earth and almost the same size. Its diameter is 7,700 miles against Earth’s 7,927 miles. Venus has a dense atmosphere; its surface is constantly veiled by clouds. But the spectroscope discloses that Venus’ atmosphere is largely composed of carbon dioxide; there is no discernible oxygen. Animal life could hardly get a foothold in such an environment. If there were vegetable life, it would have converted some of the carbon dioxide into oxygen. Dr. Jones considers that Venus is more or less in Earth’s condition of a billion or so years ago, that it is still too hot there for life to get started. He believes that when the sun’s heat output has dwindled, life on Venus may get under way.

If, biologically speaking, Venus appears much younger than Earth, then Mars appears much older. It is smaller and colder than Earth, has lost most of its atmosphere and water. But a thin atmosphere it still has, perhaps containing a little oxygen. And Mars has a little water, as the white polar caps show. These caps melt in the Martian summer, accumulate again in winter. The excitement over possible Martian inhabitants was started in the 19th Century by the Italian astronomer Schiaparelli, who described hazy streaks on the surface, called them canali. This Italian word means “channels,” was erroneously translated “canals,” which connotes intelligent engineering.

The canali do not show up clearly in photographs, because the photographic image of the planet is so small that a time exposure is necessary, and the turbulence of the earth’s atmosphere then blurs the detail. The streaks show up better to visual observation, but observers disagree on what they see.

Modern consensus, says Astronomer Jones, is that the markings are not canals but natural formations of some sort. So the existence of intelligent beings, or even of any animal life, on Mars is still anybody’s guess. If there are any Martian creatures, they must have adapted themselves to a very slow rate of oxygen intake. But all observers agree that there are distinct seasonal changes in some of the Martian markings. Certain dark areas are green in summer, grey or brown in winter. It is hard to conceive that these changes could be caused by anything but vegetation. And there, at last, is good evidence of life on another world.

Might there be life on other planets too far away for astronomy to find? In the visible universe there are about 100,000,000 other star-clouds like the Milky Way. If in each of these, on the average, there is one star with planets, that makes several hundred million planets. Many of these must be too hot or cold, too big or little, or lack suitable atmospheres and moisture. But on some, by the sheer law of averages, the conditions should be favorable for life. Astronomer Jones believes that where the conditions are favorable, life will arise. He believes that life is widely but thinly spread through the universe.

* The London wartime blackouts have aided Greenwich astronomers by cutting out the glow of city lights which interfered with telescope observation—but, presumably, the big fires set during mass raids have been a nuisance. Before the war there was serious talk of moving the observatory to another and darker site. Up to last week the observatory had not been hit and work was proceeding normally.