The Mountains of the Moon

The lack of air is considered by many astronomers to furnish the explanation of the enormous number of “craters” which pit the moon’s surface. There are about a hundred thousand of these strange rings, and it is now believed by many that they are spots where very large meteorites, or even planetoids, splashed into the moon when its surface was still soft. Other astronomers think that they are the remains of gigantic bubbles which were raised in the moon’s “skin,” when the globe was still molten, by volcanic gases from below. A few astronomers think that they are, as is popularly supposed, the craters of extinct volcanoes. Our craters, on the earth, are generally deep cups, whereas these ring-formations on the moon are more like very shallow and broad saucers. Clavius, the largest of them, is 123 miles across the interior, yet its encircling rampart is not a mile high.

THE MOON

Mars and Venus are therefore the only planets, besides the earth, on which we may look for life; and in the case of Venus, the possibility is very faint. But what about the moons which attend the planets? They range in size from the little ten-miles-wide moons of Mars, to Titan, a moon of Saturn, and Ganymede, a satellite of Jupiter, which are about 3,000 miles in diameter. May there not be life on some of the larger of these moons? We will take our own moon as a type of the class.