Gravity on its surface is only 38 per cent of terrestrial gravity--i.e., a one hundred-pound weight removed from the earth to Mars would there weigh but thirty-eight pounds.

Mars evidently has an atmosphere, the details of which we shall discuss later.
The poles of the planet are inclined from a perpendicular to the plane of its orbit at very nearly the same angle as that of the earth's poles, viz., 24 deg.

50 min.

Its rotation on its axis is also effected in almost the same period as the earth's, viz., 24 hours, 37 minutes.
When in opposition to the sun, Mars may be only about 35,000,000 miles from the earth, but its average distance when in that position is more than 48,000,000 miles, and may be more than 60,000,000.

These differences arise from the eccentricities of the orbits of the two planets.