It is not at all certain that Saturn, more than Jupiter, has any solid
surface. Indeed, it is almost certain that it has not. It is surrounded
by an atmosphere of great density, and we do not at any time see the
surface of the planet. It is believed probable that it is at least
largely in a liquid state, if not to a great extent even gaseous.
The planet is certainly not in any way dependent on the sun for the
extraordinary heat that everything indicates it to have, and its
surface is brighter than it is believed it could be if shining only
by the reflected light of the sun. This does not mean that Saturn is
self-luminous; but it is nearly certain that it is extremely hot and
glowing, and its brightness may be in part due to its own internal
fires and the extremely luminous and dense atmosphere that surrounds
it. It receives one hundred times less heat and light from the sun
than we do. If it depended entirely upon the sun for its heat,
the temperature would be nearly three hundred degrees below zero,
Fahrenheit. It is probably not only very hot itself, but its heavy
atmospheric envelope perhaps allows comparatively little heat to escape.
Its surface is belted and spotted somewhat after the manner of
Jupiter’s, but, being so much farther from us than Jupiter, it does not
disclose its surface features with the same distinctness. Apparently
it is much less turbulent than Jupiter; but even this we are not quite
certain of, and it may seem more placid because we do not so well see
its agitations.
Like all the outer planets, it differs in its constitution from the
earth and the other inner planets. Its atmosphere contains compounds
with which we are not familiar, and the body of the planet itself is
rarer and lighter, and less condensed, and in a much earlier stage of
evolution than the earth and the small planets so comparatively near us.