February 21 1962 - A Living Universe?

Everyone wants to know the answer to the question 'Is there life on other worlds?' Much, of course, depends upon what is meant by 'life'; we have good evidence that living organisms flourish on Mars, but conditions there seem unsuitable for advanced life-forms, and if we are to find other intelligent races we must, presumably, go beyond our Solar System. Whether this will ever be possible seems to be highly dubious.

However, there was much to be said about the whole matter, and it was even possible to do some practical experimentation, which was undertaken on behalf of The Sky at Night programme by Dr F. L. Jackson, the London research bacteriologist who is also an amateur astronomer (in 1963 he succeeded me as Director of the Mercury and Venus Section of the British Astronomical Association). Jackson's preliminary results were reported in the programme of February 1962, and subsequent work has not altered the conclusions given then. We also discussed the possibility that certain meteorites might contain organic materials. There was much argument about this going on at the time, and the controversy still continues, though it is probably true to say that few authorities have much faith in the organic content of meteoritic bodies.

In the article as printed below, I have deleted one paragraph relating to Venus. In 1962 it was still thought possible that Venus was a watery world, with wide oceans and - perhaps - primitive marine life; since then, the U.S. rocket Mariner II has sent back information which, if correct, shows the planet to be overwhelmingly hostile, though definite doubts remain.

Spectacular developments are taking place in the space research programme. The orbital flight of Colonel Glenn has shown that the American workers have made tremendous progress during the past months, and the idea of sending a man to the Moon no longer seems in the least fantastic. Science fiction is rapidly turning into science fact.

Yet although the achievements of Gagarin, Titov, and Glenn have understandably received the most publicity, it is important to bear in mind that manned flight is only one part of the general research programme - and at the moment it may not even be the most important part. Scientists all over the world regret that the attempt to land a Ranger probe on the Moon was not successful. No doubt another experiment on the same lines will be made soon; launchings have been scheduled in the United States, and there is every reason to suppose that it will not be long now before more striking achievements come from Russia. The Moon,) virtually without atmosphere and in every way a hostile world, is neverthe­less a perfect site for an experimental laboratory, whether manned or purely automatic.

This brings us on to an old problem which has come to the fore again recently: Is there life on other worlds? When we reach Mars and Venus, for instance, what are the chances of our coming face to face with intelligent beings, or even with animals?

So far as our Solar System is concerned, it must be agreed at once that the chances of anything of the kind are remote. Most of the planets and their satellites are hopelessly unsuited to terrestrial- type life; the giants, as well as Pluto, are much too cold, and in addition the giants lack solid surfaces, while their atmospheres are poisonous. Mercury, moving round the Sun at an average distance of a mere 36,000,000 miles, has a captured rotation, so that part of its surface is permanently sunlit while another part is plunged into everlasting night. It is true that there is a zone, between these two extreme regions, from which the Sun would appear to rise and set; but Mercury too is almost without atmosphere, and the chances of life surviving there are so slight that we are justified in dis­counting them.

This also applies to the Moon. There is a possibility that primitive living organisms survive beneath the lunar crust, par­ticularly if they have access to a supply of moisture; but there is no evidence in favour of this theory, and what evidence we have is all to the contrary. We are left, then, with two worlds: Venus and Mars.

Venus is a puzzle. It is a brilliant object in our skies, but although it is almost the same size as the Earth, and may approach us within a distance of 25,000,000 miles, we know remarkably little about it.

Dr F Jackson demonstrates what would happen to a cactus plant under Martian conditions

Mars has always been regarded as the planet most likely to harbour Earth-type life. Owing to its greater distance from the Sun, its average temperature is lower than that of the Earth, but it seems not to be a frozen world; a recent hypothesis by V. Davidov of the USSR, according to which Mars is covered with ice and has an underground hydrosphere, has not met with much support. The atmosphere is relatively thin, and is poor in oxygen; according to G. de Vaucouleurs, the bulk of the mantle consists of nitrogen, together with a certain amount of carbon dioxide and a little argon. There can be no doubt that terrestrial mammals would perish instantly if exposed to Martian conditions, and little faith is now placed in the famous 'canals', which caused so many arguments half a century ago. It is almost universally agreed that whatever the canals may be, they are natural features of the planet.

Yet Mars cannot be ruled out so far as living organisms are concerned, even though advanced forms seem to be most improb­able. One way to gain information is to simulate Martian condi­tions as far as possible, and see whether primitive organisms can endure them. Work of this kind has been done in America and in Russia, and in late 1960 new work was initiated by the Sky at Night programme. The experiments were conducted by Dr Francis Jackson, in London. Special containers were filled with 'atmo­sphere' of Martian composition and density; the 'soil' was inserted in accordance with the best information as to Martian conditions, and the correct alternation of day and night temperature was given. It has been justifiably said that the climate of Mars is of exaggerated Continental type. Midsummer days on the planet's equator may be quite warm, and a thermometer would register at least 70 degrees Fahrenheit, but during the night the temperature must fall to a level below that of the coldest areas of our Arctic and Antarctic. The thin Martian atmosphere is by no means efficient at blanketing in the Sun's warmth.

103A preliminary report was made by Jackson in 1961. As expected, higher forms of terrestrial plant life proved unable to endure the conditions, and there was no point in carrying out any extensive experiments with them. With microscopic forms, however, the situation was less obviously discouraging, and some types of bacteria appeared to survive reasonably well.

The work has now been in progress for more than a year, and the second report fully confirms the conclusions reached in the first. Only certain bacteria can live for more than a short time; those which require little or no oxygen are most suitable. Bacteria which can produce resistant spores can survive, and even a few which are unable to produce such spores have managed quite well. There must of course be a good deal of uncertainty, for our informa­tion as to the amount of moisture available on Mars is still incom­plete, but the general conclusions are founded upon an experi­mental basis.

Fungi and algae have not survived well in the containers. Moreover, it seems unlikely that any terrestrial lichens could survive on Mars. It is often said that Martian organisms may be of the lichen type, but there is no evidence in favour of this idea; all we can say is that any Martian organisms are not likely to be more complex than lichens of the sort with which we are familiar on our own world.

Research is continuing, and a third report will be made in due course, but it must be borne in mind that the experiments are limited in scope. Even if it were proved that certain forms of terrestrial organisms could survive on Mars, this would still give no evidence that life of any sort actually does exist on the planet. The recent spectroscopic work by W. M. Sinton, in the United States, lends support to the hypothesis that the famous dark areas, visible with any small telescope when Mars is well placed, are due to living organisms; but it would be premature to say that the question is definitely settled.

The most stimulating development of ideas regarding possible indigenous life on other worlds concerns meteorites. In particular, new analyses of the meteorite which fell at Orgueil, in France, as long ago as 1864 have been highly fruitful, and if the conclusions are confirmed they will lead to a drastic revision of many ideas which have been held up to the present time.

Meteorites are of several types. Some (the siderites) are irons, while others (the aerolites) are stony. There seems no chance that organic matter can exist in either siderites or aerolites, but we are less certain when we come to consider the carbonaceous chondrites, of which only a relatively few have been recovered. The Orgueil meteorite is of this type. Before impact it broke up, and some twenty pieces were found, the largest of which was about the size of a man's head. Several of these pieces are now in the Geological Museum at South Kensington.

Over the years various investigators have reported the presence of carbon compounds in meteorites. Some of the chemicals found are, it is said, similar to the constituents of terrestrial living things - though there is no proof that they originated from living matter. Recently, Claus and Nagy, in New York, have carried out micro­scopic examinations of five samples from carbonaceous chondrites. In three samples they found structures not unlike terrestrial algae, and similar though less well-defined forms were found in the remaining two samples. Even more interesting was the discovery, in two samples from the same meteorite, of a type of structure quite unlike any known terrestrial species. The results of micro- chemical investigations also suggested that decidedly complex chemical compounds might be present.

So far the conclusions are highly tentative; but if any of these structures really are the remains of algae, it is reasonable to suppose that they developed in a watery medium. This brings us on to the question of how the meteorites themselves were formed. Again we are on uncertain ground, because there is as yet no general agree­ment about exactly how the Earth and other planets came into being. At any rate, there are two main theories with regard to the meteorites. Either they represent the debris left over after the birth of the main planets, or else they are the remains of a former planet (or planets) which met with some mishap and disintegrated. There is, for instance, a chance that two planets which once revolved in orbits between those of Mars and Jupiter collided, producing the fragments now called meteorites.

It should be added that there is an essential difference between meteorites, whether irons or stones, and normal shooting-stars. The average shooting-star is smaller than a grain of sand, and there is no known case of a meteorite emanating from a shooting- star shower. Meteorites are much more nearly related to the minor planets or asteroids, most of which keep to the region between the orbits of Mars and Jupiter. Ceres, the largest asteroid, has a diameter of 430 miles, but is exceptional; the lesser members of the swarm are very small indeed, and most authorities consider that there is no basic difference between a large meteor and a small asteroid. On the collision or disintegration theory, then, the asteroids too once made up part of the former planet or planets.

One point must be obvious at once. If it can be shown that some meteorites contain traces of life, we must agree that this living material originated on a world of considerable size. In fact, the planet which broke up was not a dead globe but a living one. This is a fascinating conclusion indeed.

It may well be that the space-research programme will go a long way towards clearing the matter up. Many meteorites must have fallen on to the surface of the Moon, and will be available for study as soon as we can obtain samples of them for laboratory analysis. In general they will be far better preserved than those which have landed on Earth, because the Moon lacks atmosphere - and, incidentally, the impact velocity would be less. Once lunar meteoritic specimens are analyzed, the problem of whether any meteorites contain genuine traces of organic matter should be capable of quick solution. We cannot yet tell when this will be, but the recent suggestion that the Russian, American, and (pre­sumably) British programmes should be combined is by far the most encouraging development of the first months of 1962, and if implemented - could well lead to a saner outlook in all branches of human activity.

The Sun is a normal star, and is only one of 100,000 million stars in our Galaxy; far away in space lie thousands of millions of other galaxies, and it would be the height of conceit to suppose that we represent the only intelligent beings in the entire universe. In fact, it is logical to suppose that the universe is teeming with life. Positive proof will be hard to obtain, but we will have made a great advance if we can show that our own tiny Solar System once contained another 'living planet' as well as the Earth on which we ourselves exist.