Owing to the undoubted permanent markings on the surface of Mars,
astronomers have been able to determine the length of its day with
much less likelihood of error than in the case of any other planet
except the one on which we dwell. It rotates on its axis in twenty-four
hours, thirty-seven minutes, and twenty-three seconds, which makes its
day nearly forty minutes longer than ours. In our greed for all too
fleeting time we may feel a little envy of these extra minutes, which
would mean so much to us if added to our day. But they do not seem so
important when we consider that while Mars is having six hundred and
seventy of these days we are having six hundred and eighty-seven of
ours, which, after all, seems to give us eighteen days more of time.
Our attitude toward the situation depends upon the point of view.
The axis of Mars is inclined to its orbit about twenty-four degrees
and fifty minutes. This is but little more than the inclination of the
earth’s axis, which is twenty-three degrees and twenty-seven minutes.
Mars, therefore, has seasons very much like ours. They are, however,
slightly more marked than ours, because of the somewhat greater
inclination of the axis of the planet; and they are nearly double
the length of ours, because it takes Mars nearly two of our years to
make its journey around the sun. Its seasons, then, are nearly six
months long, while ours are but three. It has frigid, temperate, and
torrid zones, practically the same as the earth has. Its greatest
inequalities of season are caused by the eccentricity of its orbit.
It is, like the earth, farthest away from the sun when it is summer
in the northern hemisphere; and in this situation it travels so much
more slowly than when it is near the sun that summer in its northern
hemisphere is seventy-five days longer than the same season in the
southern hemisphere. The northern summer and the southern winter are
each three hundred and eighty days long, while the reverse seasons in
each hemisphere are only three hundred and six days long. The northern
summer is not only longer but also cooler than the southern, and
the northern winter is shorter and warmer than the southern. Which
hemisphere has the more favorable climate depends upon what is needed
on Mars to maintain life. It may be that in this regard the shorter,
hotter, southern summer is the best season the planet affords.