Is There Life On Earth?

Press, Volume CIV, Issue 30919, 27 November 1965, Page 5

Is There Life On Earth?

[By ROBERT C. COWIN. Nature Science editor of the “Christian

Science Monitor.”] TX) judge from weather - satellite pictures, there is no life on the earth.

Of course, the cameras carried by the Toroses and Nimbuses were not designed for biological searching. Yet, for scientists interested in planetary exploration, trying to find hints of life in weather satellite pictures is more than a fruitless game.

It helps pin down the kinds of things that might hint of life in photographs of other planets sent back by unmanned probes. Weather satellite pictures show somewhat more detail than do the photographs of Mars sent back last summer by Mariner 4. Yet they are challenging enough to sharpen the skills of planetary detectives.

Dr. Carl Sagan, of Harvard University, an astronomer interested in this photointerpreting puzzle, says it helps one learn just what to expect from pictures of a given resolution. Resolution is a measure of a photograph’s ability to show detail. The Mariner pictures of Mars, at best, had a resolution of about three kilometres. Tiros and Nimbus pictures have resolutions ranging between a few kilometres to a few tenths of the kilometre.

This means that two points a kilometre or so apart should just show up as two separate points. Closer together, they appear to be a single blur.

Features whose distinctive patterns depend on forms with characteristic dimensions smaller than about a kilometre are unrecognisable in the satellite pictures. Thus one would not expect to see buildings, people, or trees. But vast road networks, canals and the like are something else again. Such linear features, unlike forms one would expect in nature, are a sign of intelligent life that might show up at a resolution of a kilometre or so. One Road Seen According to Dr. Sagan, looking for such signs is both disappointing and instructive. In the first place, presumably obvious features like roads do not show up well at all. To illustrate this, he showed a weather satellite view of the United States’ north-eastern seaboard. Long Island and Cape Cod stand out clearly. But where is New York, or Boston, or the great turnpike network that laces through the region? At a resolution of about a kilometre megalopolis disappears. Dr. Sagan noted that some of the shadings in the picture probably are due to vegetation. But, unless one knew

this to begin with there would be no way to tell it from the picture itself.

If it is hard to find even the large-scale works of man, what about seasonal changes of vegetation such as large deciduous forests? Dr. Sagan has studied weather-satellite photos of a well-forested region taken over the seasons. The low resolution of the pictures, plus vagaries of lighting, wash out distinctive changes. In short, most of the things one would think to look for in searching for signs of intelligent beings or lower forms of organic life don’t show up well at a resolution of about a kilometre. Yet the searching of Dr. Sagan and others has not been sterile.

Out of about 1000 pictures, one road was seen. It is U.S. 40 going into Memphis. It was identified as a road because of its linearity and because it cuts across rivers at right angles. It was visible because an extra wide swath had been cut for it through a forest. In time, the contrast between swath and forest will disappear. The road then will not show up in such a picture. Another picture shows a series of dark and light parallel bands in Ontario. These look too regular to be natural. In fact, they are swaths cut by lumbermen in a forest. Snow makes the swaths stand out against strips of trees left standing.

“Suggestive” Signs Other “suggestive” signs are streaks found in some photos that may be wakes of ships or contrails of jet aircraft, or at least clouds formed along the line of contrails. None of these features would be proof of intelligent life were they found in comparable photos of another planet. But they could be a strong stimulus to more detailed searching. For example, if enough trails of vehicle were found, their pattern would indicate intelligent activity. In like manner, “unnatural” rectilinear patterns would be suspect. The lumbering scars in Ontario show that such signs of intelligent activity will show up at resolutions of about a kilometre. Such a pattern, incidentally, was found in some of the Mariner photos of Mars. But Dr. Sagan says it probably is due to some quirk of the photo processing. The weather-satellite pictures thus show that Marinertype pictures, even if taken by the thousand, can never do more than tantalise those seeking signs of life. But with a boost of resolution of only

30 times, man's works on earth show up clearly.

Such improved resolution is being planned for cameras on satellites to be sent to orbit Mars within a decade. If any beings have left marks on that planet comparable to cities, roads, or canals, we can then expect to see them.