JF Ptak Science Books Quick Post
This fine image from Popular Mechanics (January 1927) imagines the Martian moon "Ganymeade", mentioning that it is only 7 miles around, and could hardly host a large city, which the artist imagined in this free-for-all concept piece. I like the idea of putting the size of the moon in perspective like this--I must say that I've never seen one quite like this. But first, the magazine identifies the Martian moon as "Ganymede", which is actually a Jovian moon. The moons of Mars are Phobos and Deimos (the names meaning panic/terror and terror/dread), and they are 13.8 miles and 7.8 miles, respectively. They were discovered in 1877 by Asaph Hall at the National Observatory, and there wasn't a "Ganymede" between them--weirdly and wonderfully, though, their existence was imagined by non other than Jonathan Swift, who had his Laputan astronomers discover two moons in Gulliver's Travels in 1726. But no Ganymede. As it turns out, Ganymede is the largest moon in the solar system, and is nearly the size of Mars, so maybe that is where the confusion started.
Anyway, this is a great image: