Second Moon?

Astronomer Clyde Tombaugh, who spotted the planet Pluto (1930), is looking for a nearer and even more elusive object: a second satellite of the earth. Since he refuses to give details and refers questioners to Army Ordnance-in Washington, it is fair to assume that the famous rocket-men who work for Army Ordnance are interested in the project. They may want merely to know what opposition from nature their rockets are apt to encounter when they climb deep into space. Or they may have a more ambitious interest: a nearby, natural satellite might be a more convenient base in space than the much-discussed artificial satellite.

There is no evidence so far that the earth has a second satellite, but Mars has two satellites, Jupiter has twelve satellites, and Saturn probably has millions of them in its rings. The earth may have picked up a few small ones. The fact that they have not been discovered yet does not prove that they do not exist.*

A small satellite close to the earth would be hard to spot. It might circle near the equator, invisible to most of the world's observatories. In any case, it would spend nearly half its time in the shadow of the earth, where it would be invisible. Most of the rest of the time it would be passing over the sunlit earth, and would look no brighter at best than a tiny fragment of the moon as seen by day. Best time to look for a small satellite would be at dawn or dusk, when it would be shining brightly above the dim-lit earth.

A satellite near the earth would have to move very fast to keep itself out of the clutches of the earth's gravitation, and its speed would make it doubly hard to spot. A miniature moon 1,000 miles above the earth would whiz around the earth in about two and a half hours, too fast for its image to be caught by ordinary photographic plates. Best way to catch it would be with a swinging telescopic camera turned to match its speed. Thousands of small areas in the sky must be examined and completion of such a search could take years. Presumably, that is what Dr. Tombaugh is doing.

*In Jules Verne's From the Earth to the Moon, a small satellite of the earth disturbed the course of the space ship and almost kept it from ever returning to earth.

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