MARS,
The fourth planet in distance from the sun, and, next to Venus, the one that comes nearest to the earth, has also to the latter some points of resemblance. Not that it is like it in size; for in fact, it is not more than about one-eighth as large; nor yet in the length of its year, which is nearly twice as long as one of our years (about 687 of our days). But it has about its equatorial regions, light and dark portions, which are generally admitted to be continents and oceans, whose distribution appears very much like that of the land and water on the earth’s surface. About the poles also appear during the planet’s winter brilliant white portions, which disappear during its summer. This is probably occasioned by the fall of snow in winter, and its melting in the spring and summer. Again, its time of revolution on its axis, which has been quite satisfactorily determined, and, indeed, much more accurately than that of any other planet, is shown to be 24 hours, 37 minutes, 23 seconds very nearly, making its days and nights very much like our own. Its seasons also resemble ours somewhat, though longer and subject to greater extremes of heat and cold. The inclination of the equator of Mars to the plane of its orbit is about 27°, or 3½° more than that of the earth; and its year being nearly twice as long and its orbit more eccentric, make the seasons in its northern hemisphere about as follows: Spring 191⅓ days, summer 181 days, autumn 149⅓, and winter 147 days (of the planet). When nearest to us, its apparent diameter is about seven times as great as when farthest away. These distances are in round numbers 35 and 247 millions of miles respectively. It appears brightest to us of course, when in opposition, that is, when we are between it and the sun, its distance from the earth at these periods varying from 35 to 62 millions of miles, making it seem four times as bright at the former as at the latter distance. On account of the inclination of the equator to the orbit, we can see 27° beyond the north pole at conjunction, and 27° beyond its south pole at opposition; hence astronomers are much better acquainted with its southern than with its northern regions. It is believed that Mars has not only land, water and snow, but also clouds and mists. The land is generally reddish when the planet’s atmosphere is clear; this is owing to the absorption of the atmosphere, as is the color of the setting sun with us. The water appears of a greenish tinge. Of this planet we have to report for this month, that it is decreasing in interest. Its diameter diminishes from 7.8″ to 6.6″. On the 2d it sets at 1:34 a. m.; on the 16th, at 12:55 a. m.; and on the 31st, at 12:13 a. m. On the 2d, at 9:01 a. m., it is 7° 9′ north of the moon; on the 5th, at midnight, 90° east of the sun; on the 30th, at 3:20 p. m., is again in conjunction with and 5° 50′ north of moon; and on the 31st, at 11:00 a. m., is 58′ north of Alpha Leonis.