THAT EVENING, after my talk with Redell, the question kept coming back in my mind.

What were they like? And what were they doing here?

From the long record of sightings, it was possible to get an answer to the second question. Observation of the earth followed a general pattern. According to the reports, Europe, the most populated area, had been more closely observed than the rest of the globe until about 1870. By this time, the United States, beginning to rival Europe in industrial progress, had evidently become of interest to the s.p.a.ce-ship crews.

From then on, Europe and the Western Hemisphere, chiefly North America, shared the observers" attention. The few sightings reported at other points around the world indicate an occasional check-up on the earth in general. Apparently World War I had not greatly concerned the s.p.a.ce observers. One reason might be that our aerial operations were still at a relatively low alt.i.tude.

But World War II had drawn more attention, and this had obviously increased from 1947 up to the present time. Our atomic-bomb explosions and the V-2 high-alt.i.tude experiments might be only coincidence, but I could think of no other development that might seriously concern dwellers on other planets.

It was a strange thing to think of some far-off race keeping track of the earth"s progress. If Redell was right, it might even have started in prehistoric time; a brief survey, perhaps once a century or even further s.p.a.ced, then gradually more frequent observation as cities appeared on the earth.

Somewhere on a distant planet there would be records of that long survey. I wondered how our development would appear to that far-advanced race. They would have seen the slow sailing ships, the first steamships, the lines of steel tracks that carried our first trains.

Watching for our first aircraft, they would see the drifting balloons that seemed an aerial miracle when the

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Montgolfiers first succeeded. More than a century later, they would have noted the slow, clumsy airplanes of the early 1900"s. From our gradual progress to the big planes and bombers of today, they could probably chart our next steps toward the stratosphere--and then s.p.a.ce.

During the last two centuries, they would have watched a dozen wars, each one fiercer than the last, spreading over the globe. Adding up all the things they had seen, they could draw an accurate picture of man, the earth creature, and the increasingly fierce struggle between the earth races.

The long survey held no sign of menace. If there had been a guiding purpose of attack and destruction, it could have been carried out years ago. It was almost certain that any planet race able to traverse s.p.a.ce would have the means for attack.

More than once, during this investigation, I had been asked: "If the saucers are interplanetary, why haven"t they landed here? Why haven"t their crews tried to make contact with us?"

There was always the possibility that the planet race or races could not survive on earth, or that their communications did not include the methods that we used. But I found that hard to believe. Such a superior race would certainly be able to master our radio operations, or anything else that we had developed, in a fairly short time. And it should be equally simple to devise some means of survival on earth, just as we were already planning special suits and helmets for existence on the moon. During a talk with a former Intelligence officer, I got a key to the probable explanation.

"Why don"t you just reverse it--list what we intend to do when we start exploring s.p.a.ce? That"ll give you the approximate picture of what visitors to the earth would be doing."

Naturally, all the details of s.p.a.ce plans have not been worked out, but the general plan is clear. After the first successful earth satellites, we will either attempt a s.p.a.ce base farther out or else launch a moon rocket. Probably many round trips to the moon will be made before going farther in s.p.a.ce.

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Which planet will be explored first, after the moon?

According to Air Force reports, it is almost a certainty that planets outside the solar system are inhabited. But because of the vast distances involved, expeditions to our neighboring planets may be tried before the more formidable journeys. More than one prominent astronomer believes that life, entirely different from our own, may exist on some solar planets. Besides Mars, Jupiter, and Venus, there are five more that, like the earth, revolve around the sun.

One of the prominent authorities is Dr. H. Spencer Jones, Astronomer Royal. In his book Life on Other Worlds, Dr. Jones points out that everything about us is the result of changing processes, begun millenniums ago and still going on. We cannot define life solely in our own terms; it can exist in unfamiliar forms.

"It is conceivable," Dr. Jones states in his book, "that we could have beings, the cells of whose bodies contained silicon instead of the carbon which is an essential const.i.tuent of our cells and of all other living cells on the earth. And that because of this essential difference between the const.i.tution of those cells and the cells of which animal and plant life on the earth are built up, they might be able to exist at temperatures so high that no terrestrial types of life could survive."

According to Dr. Jones, then, life could be possible on worlds hotter and drier than ours; it could also exist on a very much colder one, such as Mars.

Even if a survey of the sun"s planets proved fruitless, it would decide the question of their being populated. Also, it would provide valuable experience for the much longer journeys into s.p.a.ce.

No one expects such a survey until we have a s.p.a.ce vehicle able to make the round trip. One-way trips would tell us nothing, even if volunteers offered to make such suicidal journeys.

The most probable step will be to launch a s.p.a.ce vehicle equipped with supplies for a long time, perhaps a year or two, within the solar system. Since Mars has been frequently mentioned as a source of the flying

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saucers, let"s a.s.sume it would be the first solar-system planet to be explored from the earth.

As the s.p.a.ce ship neared Mars, it could be turned to circle the planet in an orbit, just like our planned earth satellite vehicle. Once in this...o...b..t, it could circle indefinitely without using fuel except to correct its course.

From this s.p.a.ce base, unmanned remote-control "observer" units with television "eyes" or other transmitters would be sent down to survey the planet at close range. If it then seemed fairly safe, a manned unit could be released to make a more thorough check-up.

Such preliminary caution would be imperative. Our explorers would have no idea of what awaited them. The planet might be uninhabited. It might be peopled by a fiercely barbarous race unaware of civilization as we know it. Or it might have a civilization far in advance of ours.

The explorers would first try to get a general idea of the whole planet. Then they would attempt to examine the most densely populated areas, types of armature, any aircraft likely to attack them. Combing the radio spectrum, they would pick up and record sounds and signals in order to decipher the language.

As on earth, they might hear a hodgepodge of tongues. The next step would be to select the most technically advanced nation, listen in, and try to learn its language, or record it for deciphering afterward on earth.

Our astronomers already have a.n.a.lyzed Mars"s atmosphere, but the explorers would have to confirm their reports, to find out whether the atmosphere at the surface would support their lungs if they landed.

The easiest way would be to send down manned or unmanned units with special apparatus to scoop in atmosphere samples. Later a.n.a.lysis would tell whether earthlings would need oxygen-helmet suits such as we plan to use on the moon.

But before risking flight at such low alt.i.tudes, the explorers would first learn everything possible about the planet"s aircraft, if any.

They would try to determine their top ceiling, maximum speed, maneuverability, and if possible their weapons. Mitch of this could be done by sending down remote-control "observer" disks, or

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whatever type we decide to use. A manned unit might make a survey at night, or in daytime with clouds nearby to shield it. By hovering over the planet"s aircraft bases, the explorers could get most of the picture, and also decide whether the bases were suitable for their own use later.

It might even be necessary to lure some Martian aircraft into pursuit of our units, to find out their performance. But our explorers would above all avoid any sign of hostility; they would hastily. withdraw to show they had no warlike intentions.

If the appearance of our observer units and manned craft caused too violent reactions on the planet, the explorers would withdraw to their orbiting s.p.a.ce vehicle and either wait for a lull or else start the long trip back home. Another interplanetary craft from the earth might take its place later to resume periodic surveys.

In this way, a vast amount of information could be collected without once making contact with the strange race. If they seemed belligerent or uncivilized, we would probably end our survey and check on the next possibly inhabited planet. If we found they were highly civilized, we would undoubtedly attempt later contact. But it might take a long time, decades of observation and a.n.a.lysis, before we were ready for that final step.

We might find a civilization not quite so advanced as ours. It might not yet have developed radio and television. We would then have no way of getting a detailed picture, learning the languages, or communicating with. the Martians. a.n.a.lysis of their atmosphere might show a great hazard to earthlings, one making it impossible to land or requiring years of research to overcome. There might be other obstacles beyond our present understanding.

This same procedure would apply to the rest of the solar-system planets and to more distant systems. Since Wolf 359 is the nearest star outside our system that is likely to have inhabited planets, one of these planets would probably be listed as the first to explore in far-distant s.p.a.ce. It would be a tremendous undertaking, unless the speed of light can be exceeded in s.p.a.ce. Since

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Wolf 359 is eight light-years from the earth, even if a s.p.a.ce ship traveled at the theoretical maximum--just under 186,00 miles a second--it would take over sixteen years for the round trip. Detailed observation of the planet would add to this period.

If we a.s.sume half that speed--which would still be an incredible attainment with our present knowledge--our s.p.a.ce explorers would have to dedicate at least thirty-two years to the hazardous, lonely round trip. However, there has never been a lack of volunteers for grand undertakings in the history of man.

It is quite possible that in our survey of the solar-system planets we would find some inhabited, but not advanced enough to be of interest to us. Periodically, we might make return visits to note their progress. Meantime, our astronomers would watch these planets, probably developing new, higher powered telescopes for the purpose, to detect any signs of unusual activity. Any tremendous explosion on a planet would immediately concern us.

Such an explosion, on Mars, was reported by astronomers on January 16, 1950. The cause and general effects are still being debated. Sadao Saeki, the j.a.panese astronomer who first reported it at Osaka, believes it was of volcanic nature.

The explosion created a cloud over an area about seven hundred miles in diameter and forty miles high. It was dull gray with a yellowish tinge and a different color from the atmospheric phenomena customarily seen near Mars. Saeki believes the blast might have destroyed any form of life existing on the planet, but even though the telescopic camera recorded a violent explosion, other authorities do not believe the planet was wrecked. The ca.n.a.ls first discovered on Mars by Giovanni Schiaparelli, about 1877, are still apparent on photographs.

Mars is now being carefully watched by astronomers. If there are more of the strange explosions, the planet will be scanned constantly for some clue to their nature.

If a mysterious explosion on Mars, or any other planet, were found of atomic origin, it would cause serious concern on earth. Suppose for a moment that it happened many years from now, when we will have succeeded in