“Let us first fly over the surface at a safe height and examine it carefully, then select a landing site,” suggested Professor Palmer. “If it seems to be inhabited we had best land outside some smaller village where we will have an opportunity to interview a few of the natives without so much danger of being overpowered if they prove antagonistic.” Sluggishly, the vast map slid westward before their gaze, in panoramic review as the planet rotated in its axis. Thus its entire surface from pole to pole was gradually presented to their view as they continued to descend at a considerably reduced speed. * * * * * The fifteenth “day” found them within about 25,000 miles of the planet’s surface. At this elevation Professor Palmer commenced a sharp lookout for the two moons which were known to revolve about Mars at great speed. These moons had been glimpsed on rare occasions by a few of the earth’s astronomers through powerful telescopes, but only when conditions for observation had been ideal. Professor Palmer had seen them more than once, although they were each approximately but ten miles in diameter, as he explained to Robert and Taggert. “Ten miles?” repeated Taggert, doubtfully. “Why--dammit, these blamed Martian moons aren’t much more than balls of mud! Say, I’d rather have our moon than half a dozen like those. Ours is more than 2,000 miles in diameter, isn’t it?” “You must remember that the Earth’s moon is about 240,000 miles away from it, while Mars’ nearest moon is only about 3,700 miles above its surface.” “How high is the other one?” “Approximately 13,000 miles; but it is doubtful whether it would be visible to the naked eye from Mars--certainly not plainly. The one nearer Mars, however, should present an interesting spectacle from that planet. It requires eleven hours to cross Mars’ heavens, by reason of the moon’s own swift revolution and the slower rotation of Mars, going through all its phases and half again during that time.” “It’s odd that it doesn’t fall into the planet from that height,” said Robert. “Rapid revolution in its orbit round Mars produces sufficient centrifugal force to balance the planet’s attraction,” said Professor Palmer. “The same principle is involved as in the swinging of a pail of water over one’s head without spilling it. Yet, some day one of these moons may be drawn into the planet. Should that happen, the blow may be great enough to change the planet’s own orbit.” “How about landing on one of these moons?” said Robert. “Ha! Novel thought, that,” exploded Taggert. “Say, if we’d play catchers on it, we would be apt to run right off.”