National Geographic : 1964 Nov
Ranger's view of Guericke Crater from 470 miles: Hitherto unseen craters appear in sharp definition. Two of the flying TV cameras scanned 1,150 lines per image, as compared to 525 lines in ordinary TV pictures in the United States. MOUNI LSON A PALOMAR OBSERTOIES Earth-based telescope picture approximates Ranger's, but atmosphere blurs details. Guericke Crater, whose filled basin and broken rim show its age, is 36 miles across; Ari zona's Meteor Crater, one of the best known on earth, is less than a mile wide. was more than a thousand times better than had been achieved with earth-based telescopes. Like all televised pictures, Ranger's had scan lines, but so much finer and more numerous than those of a standard television screen that they looked like direct photographs. What had been mere specks through the telescopes became clear, crisp shapes. In the closest shot we saw forms no bigger than a small boy. We had little time and a lot to look at, but all of us noted at once the single greatest fact revealed by Ranger 7's cameras: The moon's surface, seen for the first time at close range, was not radi cally different from our idea of it. To scientists, confirmation is as val uable as information. Since Dr. Kuiper THIS PAGE FOLDS OUT and I have shared responsibility for tell ing the builders of future moon-landing vehicles what kind of terrain their ma chines would encounter, this discovery was deeply gratifying. I headed back to my laboratory in Flag staff, Arizona, elated and relieved. There was urgent work to be done connected with space projects already under way. Mapping the geology of the moon was, and is, our main occupation. We are con cerned not only with topography, but also with the distribution of different kinds of rock and the effects of forces that shape the surface. To a degree, we map the moon the way the Geological Survey maps the United States. Several quadrangle maps are finished - each covering an area about the size of Arizona. The whole equatorial area of the moon will be mapped by the end of this year; this is the region in which our first manned craft will land. In three or four years we'll have mapped the whole visible side-about 50 quadrangles in all. This geological mapping was the basis of my own pre-Ranger "model"-my personal conception-of what the moon might be like, close up. To explain what the Ranger pictures mean to me, I must first explain my mental picture and how I arrived at it. As it turned out, it wasn't far wrong. Craters Pock Lunar Plains There are differences, of course, between my mental picture and the real thing. All of us had tried for years to second-guess the results of Ranger's success. Each of us 702 was surprised differently, according to his own preconceptions. And there are still dif ferences between thoroughly qualified scien tists as to what Ranger 7 taught us about the moon's surface. I give you my own conclusions. We can set aside the various theories of lu nar origin; Ranger's pictures for the most part don't bear on it. It's the surface we care about right now. We want to put a man on it. Our satellite's main features have been known for centuries: rugged mountains; rocky, plainlike areas called maria, or seas (by Galileo, who thought they were); and cra ters. The moon is so pock-marked that even its craters have craters. Hundreds of thou sands of them can be counted from earth. The biggest are hundreds of miles across, and, prior to Ranger 7, we could see smaller ones down to our frustrating limit of visibility.