Mars (One of the superior planets)

Collier's New Encyclopedia (1921)

one of the superior planets situated between the earth on the one side and the vast cluster of asteroids on the other. Its mean distance from the sun is 141,500,000 miles, and at times it is only 36,000,000 miles from the earth. It revolves around the sun a few minutes under 687 days, and rotates upon its axis in 24 hours, 37 minutes, 22.67 seconds. Its equatorial diameter is about 4,200 miles, its polar about 40 less. Its mass is about one-eighth that of the earth. When at its greatest distance from the earth its telescopic di diameter is less than four seconds of are, but when nearest this is increased to 24 seconds, hence the planet varies greatly in brightness. Viewed by the naked eye, Mars appears of a uniformly red and fiery tint; but looked at through a powerful telescope the ruddy color is found to be confined to certain definite areas. In 1877, Hall, of the Observatory at Washington, by the aid of the great Washington refracting telescope, discovered that Mars has two satellites. The outer moon, named of " Frank Deimos, is estimated to be from 5 to 6 by " The miles in diameter, and revolves around , " " Jacob the planet, at a distance of 12,500 miles, of a Fa- in 30 hours, 18 minutes. Phobos, the in- Midshipman ner moon, is but 3,700 miles from the Tales, " " The planet, and completes its revolution " Snarley- around Mars in 7 hours, 39 minutes. This " Percival is much less than the period of rotation , " " Poor of Mars itself, and constitutes a unique Langham, fact in the solar system, which has furnished forcible corroboration of Darwin's theory of the tides. Certain markings on the surface, known as "Canals," have caused much speculation among astronomers. A certain similarity with earth conditions has created a theory that Mars might be inhabited, and serious efforts have been made, notably in 1920, to communicate with the planet by wireless telegraphy.