Space: Quarter Earth in the Sky

At first glance, it seemed to be merely a photograph of a quarter moon in the night sky. What made the picture remarkable was that it actually showed a quarter earth, reflecting sunlight in the dark lunar sky. It was the first photograph of earth ever taken from deep space, and it was shot by Lunar Orbiter 1 from a point only 27 miles above the surface of the moon. Clearly visible in the foreground was part of the lunar surface marked by its familiar craters. But most of the visible portion of the earth was covered by swirling white clouds that obscured the outlines of the terrestrial continents.

Scientists had ordered the picture shot to show the earth’s terminator line —the boundary between the daylight and nighttime hemispheres—which they had predicted would be fuzzy and indistinct because of the earth’s atmosphere. Inspection of the first rough print of Orbiter’s picture showed a terminator about as sharp as that on the moon —which has no atmosphere.

Displaying the precise control of a teen-ager over a spinning Yo-Yo, controllers at Pasadena’s Jet Propulsion Laboratory maneuvered Orbiter ever closer to the moon’s surface in an attempt to eliminate the fuzziness of its high-resolution camera shots (TIME, Aug. 26). Acting after a suggestion from Eastman Kodak technicians that the camera might begin returning clear pictures of possible astronaut landing sites if it were operated from an altitude of 25 miles, they fired Orbiter’s retrorocket for three seconds, reducing the low point of its orbit from 30.4 to 25.1 miles, and got it into position for more photography.

On the basis of preliminary data reflecting eccentricities in the spacecraft’s orbit, scientists came to an unexpected conclusion: the moon, like the earth, may be slightly pear-shaped. Instead of being a perfect sphere, the moon seems to be depressed about a quarter of a mile out of shape at its south pole and bulges out about the same distance at its north pole. Because the moon has a diameter of about 2,200 miles, the distortion would hardly be noticeable when viewed from the earth. Said a NASA official: “Let’s not expect to go out and look at the moon tonight to confirm this.”