A Visit with Mars

SCIENCE

The planet Mars was bigger, brighter, and closer to the earth last week than it has been in 32 years. On Sept. 7 it passed within 35,200,000 miles. Not until 1971 will it come so close again.

The earth, moving faster on its smaller orbit, overtakes and passes Mars every 26 months, but the distance of closest approach varies considerably because both orbits are slightly elliptical, with their long axes pointing in different directions (see diagram). The earth may overtake Mars at a point where the orbits are close together, as they are this week, or where they are almost twice as far apart.

For both astronomers and science fiction writers. Mars is the king of planets. Its atmosphere is dense enough to make life possible, but not so dense that it hides the surface, as does the cloudy white atmosphere of Venus. There is water on Mars -- not much, but some. Thin winds carry clouds of several types. The color of the surface changes blotchily with the seasons, as if vegetation were growing. There is a wealth of fine detail just at the threshold of vision, but even the best astronomical instruments have not been able so far to take photographs of it. Some astronomers say they see the famous "canals"; some see streaky, irregular lines; others see little that is definite. They all agree that something complex and interesting exists on Mars, but they do not know what it is.

New Tricks. Mars came fairly close in 1954. but it could be observed effectively only from the earth's Southern Hemisphere, where observatories are few. So 1954 was a kind of dress rehearsal for this year's event. Astronomers have devised new tricks and instruments. Much of their equipment has improved materially in the last few years. Photographic films are faster and finer-grained. They may have improved enough to get a photographic record of the fleeting Martian details that visual observers believe they have seen. If plain telescopic photography does not succeed, one of the several electronic devices that amplify light may do the trick.

Even if the astronomers do not get better pictures of Mars, they will surely learn new facts about it. Such fast-improving devices as the infra-red spectrometer will tell new details about the composition of the Martian atmosphere.

Yellow Planet. As Mars drew close last week, even laymen noticed that it could hardly be called red. This time it looked definitely yellow. One reason for this, reported astronomers from Japan to Texas, was a gigantic, yellow dust cloud, presumably raised by unusual turbulence in the Martian atmosphere. It was first seen by Japanese astronomers in the middle of August. Later it spread until it obscured much of the planet's surface, making all observation difficult.

Astronomer Gerard P. Kuiper at the University of Chicago, working at the McDonald Observatory, Texas, reported another color change on Mars. Its dark areas, which are generally supposed to be some sort of vegetation, are unusually drab this year. They are neutral grey, instead of the dull green that he had expected.

The dust will presumably settle before Mars gets too far away for good observation. For another month at least its distance will not increase enough to make any appreciable difference. The astronomers, however, cannot report all their findings immediately. They will need much time for study and coming to conclusions. In fact, the public may not get the latest news from Mars until the formal meeting of the International Mars Committee in June 1957.

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