September 7 1962 - Can the Planets be Contaminated?

In September 1962 the Mariner II vehicle was on its way toward Venus, and keeping to its calculated course. No landing was to be attempted, but the very fact that such an experiment had become possible underlined the need for thorough decontamination of all space probes which might actually reach other worlds. An emphatic statement to this effect had been made by Professor Sir Bernard Lovell, who made a recording for the programme; a recording was also made by Dr George Hobby, who was in charge of the decontamina­tion involved in the United States Ranger project, and Dr F. L. Jackson was in the studio with me. At the time of writing (July 1964) full international agreement on the matter is still lacking, and so the danger of unintentional contamination remains.

Space research has progressed much more quickly than would have been thought possible even a few years ago. Problems have been encountered and have been solved, only to be replaced by new ones - some of which have been decidedly unexpected. Among these new problems is that of the possible danger of contamination, both to other planets and to the Earth itself.

The idea is far from new. H. G. Wells used it in his famous novel The War of the Worlds, in which Earth is attacked by intelligent but utterly alien beings from the planet Mars, who cause immense devastation before they are finally destroyed. In Wells' story, the Earth is saved not by the efforts of men but because the Martians cannot resist terrestrial bacteria, and are killed together with the 'red weed' which they brought with them. This is pure fiction, and no modern astronomer is likely to believe in intelligent Martians, alien or otherwise; but there can be no doubt that the problem of unfamiliar bacteria has become unpleasantly pressing. Rockets have already landed on the Moon, and others will follow in the near future, while Mars and Venus are other obvious targets. The trouble is that contaminants may be carried by an unmanned vehicle just as easily as in a probe carrying a human crew.

There are two main aspects to be considered. First is the danger of carrying terrestrial contamination to other worlds, and thereby doing future scientists a grave disservice. We need have no fear of encountering other intelligences; conditions on the Moon are hopelessly unfavourable, and neither is it at all likely that advanced forms of life will be found on Mars or Venus. However, we have a great and unique opportunity to examine these planets in their undisturbed form. As soon as terrestrial contamination is intro­duced it will be permanently impossible to disentangle the Earth organisms from those which are indigenous to the planet. A single mistake will be enough, and the opportunity will never recur. As has been pointed out by Professor Sir Bernard Lovell, anything of the sort would be a moral disaster as well as a scientific one, since Man would be assuming the right to interfere with the possible organic development in an environment which does not belong to him. To explode a nuclear device upon another world would, of course, be sheer madness, but fortunately it does not appear likely that such an experiment will be carried out.

We have considerable information about our own environment, and about the bacteria which might be carried from Earth to the Moon or a planet. However, we do not know nearly so much about possible organisms which might be encountered elsewhere; and this leads on to the second aspect of the problem - that of con­taminating the Earth. Suppose that an automatic probe is sent to another world, and is then brought back again? With it might come organisms which could be unwelcome or even dangerous. This theme, too, has been used often enough by science-fiction writers, but the problem is both real and serious. We are investi­gating completely new fields of research, and we cannot afford to take the slightest risk.

The Moon is our first space-target, and here the contamination dangers are less than for Mars or Venus, because the Moon is virtually devoid of atmosphere. Neither can free water exist at the surface, and there is no evidence in favour of either subsurface water or of ice. Yet in the remote past it is not inconceivable that the Moon possessed both atmosphere and water - in which case interesting .chemical substances could have been formed, and would presumably still be present. It is not likely that any sort of life exists on the Moon now. There have been suggestions that the pioneer explorers will find fossils in the lunar crust; personally I am more than dubious, but the possibility cannot be entirely ruled out.

Because of the Moon's hostile nature even the lowliest terrestrial organisms would have great difficulty in surviving, even over limited periods, if sent there. Yet it must be emphasized that our knowledge of the nature of the Moon's crust is still far from com­plete, and sterilization of all vehicles is still vitally important. Unfortunately there is still no clear-cut statement from Moscow about the precautions taken with Lunik II, which crash-landed on the lunar surface in September 1959; we can only hope that they were effective. With the United States 'Ranger' programme, great attention has been paid to the whole question of contamination, and all things considered it does not appear that the first two probes have done any harm.

Mars is entirely different, and here it seems that we are dealing with a living world instead of a dead one. There are excellent reasons for believing that the dark patches on the surface, visible with a small telescope when the planet is reasonably well placed are made up of living organisms of some kind. Their precise form is, of course, unknown. There is no justification for saying, as some writers have done, that they are lichens or mosses; they may in fact be totally unlike any organisms found on Earth. However, it is reasonable to suppose that they are no more highly developed than our lichens and mosses, since the Martian environment is not particularly favourable. The atmosphere is thin, as well as being deficient in oxygen and water-vapour, while the night tempera­tures are extremely low.

Lowly organisms of Earth type could probably survive on Mars as has been demonstrated by laboratory experiments carried out in the United States and the USSR as well as by F. L. Jackson in England. A single contaminated rocket landing on Mars could therefore do an incredible amount of harm from a scientific point of view, and neither can we discount the suggestion that some Martian organisms might be dangerous if brought back to Earth. It would be very difficult to decontaminate a wide area, and the only sensible solution is to leave a returning Mars-probe in orbit round the Earth until complete decontamination has been ensured.

Automatic probes may, of course, yield valuable information on this point. It might be possible to land a suitably constructed and efficiently decontaminated microscope on Mars (or, for that matter, on the Moon) which would analyse material gathered from the surface and send back its findings by means of television techniques. However, experiments of this sort can hardly be expected for a while.

Let us now consider some of the safety precautions which have been planned, one or two of which have already been put into effect. It may be desirable to launch a thoroughly sterilized vehicle in an outer casing, which will later be discarded. During its passage through the Earth's atmosphere, the casing may become undesirably contaminated; but when it is beyond the atmosphere, the casing will be broken free and will fall back to Earth, leaving the decontaminated vehicle to continue its journey alone. Apparently this was not done with the first lunar probes, and neither has it been considered necessary with the Mariner probe to Venus, because no actual landing is contemplated; it is not likely that the Mariner will approach Venus much within 10,000 miles, so that it will remain well beyond the planet's atmosphere. * Yet the procedure may be adopted with future Moon vehicles, and with rockets designed to land on Venus or Mars.

The actual sterilization of a capsule is fraught with considerable difficulty. For example, the capsule cannot be swamped in disin­fectant solution; neither can the bacteria be killed by extreme heating of the capsule's interior, since this would ruin the delicate electronic apparatus.

A much better method involves bombardment by gamma-rays, and in fact gamma-ray decontamination is already being used at the Research Laboratories of the United Kingdom Atomic Energy Authority as well as in some branches of industry. Gamma-rays are highly penetrative, and can reach all parts of even the most complicated equipment. The source of the rays is radioactive cobalt - cobalt-6o, to give it its technical designation.

The radioactive element is placed at the centre of the irradiation plant, and the boxes containing the materials to be sterilized are placed in airtight packages. They are then loaded at one end of a conveyer belt, which carries them into a huge concrete cell. Once inside they are moved slowly round the cobalt element until they have been bombarded with sufficient radiation to kill off the bacteria. Materials of all kinds - including items such as bandages, hypodermic syringes and blood transfusion sets - may be treated thus. At present the full capacity of the irradiation plant is let to British industry, but plans have been made for increasing the amount of cobalt-6o so that further work may be undertaken.

Another method of sterilization is to use the gas known as ethylene oxide, which is lethal to bacteria and viruses. The prin­ciple involved is that of a gas chamber - somewhat reminiscent of the German gas-chambers of twenty years ago, but now being put to sane and worth-while use. The first essential is to make sure that the chamber is perfectly airtight (a space capsule, of course, would act as its own chamber). It is then evacuated, and filled with ethylene oxide. After a suitable period, the equipment, contained in permeable bags, is tested to establish whether it is in fact free from bacteria. Gas-chambers may be of considerable size - large enough to deal with a capsule the size of, say, Friendship 7, which carried John Glenn into orbit. (It was not, of course, necessary to decontaminate Friendship 7 itself, which was merely an orbital vehicle and not a space-probe.) Even astronauts' suits could be treated in this manner.

It is clear, then, that these and other methods should prove at least reasonably adequate. Let it be said at once that we cannot hope to ensure complete decontamination, and the risks cannot be entirely eliminated, but they can be made very slight. Yet it must again be stressed that a single careless mistake might easily lead to scientific disaster, and for this reason it is essential that no probe designed to land upon another world should be launched without a very complete 'all-clear' from scientists who specialize in the problems of decontamination. International agreement must be secured, and it is here, perhaps, that the main danger lies.

It has become painfully clear that international agreement is difficult to obtain even in small matters, and it is also, unfortu­nately, true that space research is closely linked with military preparations (a fact which will be deeply deplored by all true scientists and, indeed, by all rational men and women). There are various international scientific bodies concerned with the decon­tamination question, notably Cospar, the International Astro­nomical Union and the International Scientific Radio Union. All these organizations have passed relevant resolutions. However, many of these resolutions have not been ratified by the Govern­ments concerned, and are not, therefore, regarded as politically binding. Until they have been universally accepted the dangers will remain.

The decision cannot be postponed. The matter is of the utmost urgency, and high-level political action is essential, presumably in the United Nations. We can only hope that the wrangles will not be as protracted as many United Nations discussions have been in recent years, and that a positive policy will not only be laid down but also carried out.

We cannot tell what developments will take place in the immediate future. With a research field which is advancing so rapidly, it is impossible to make forecasts for as much as a year ahead. Yet it will indeed be strange if automatic probes, at least, have not been established and recovered from the Moon before long, and there is no reason to doubt that probes will also be landed on Mars and Venus. This is why the decontamination problems must be tackled without delay. It would be more than tragic if scientists of the 2o6o's were still handicapped by the scientific activities of the hotheads of the nineteen-sixties.