During the time of its rotation it changes four times from full
to new and new to full. The appearance of this satellite to the
Martians is equal, if not a little brighter than the view of
Jupiter from your Earth.

The second satellite, known to us as Benii, and to your
astronomers as Phobos, sheds considerable amount of light on the
Martian landscape by means of its large size and close proximity,
being distant about 3,700 miles from the surface of Mars. This
satellite is shut out from view beyond 69 degrees latitude by
reason of the curvature of its primary. Its period is 7 hours
and 30 minutes--less than one-third the time of the rotation of
Mars. It rises in the West and courses across the Heavens in 11
hours, during which time it undergoes one entire cycle of its
phases and gets through half another. Its disc appears to us as
a little more than half of the moon's disc on your Earth at full
appears to you.

The realm of Physics presents another interesting study to the
Martian student. We have advanced to the study of Nature's laws
to a point which would appear to your understanding most
incomprehensible. Long ago we mastered the knowledge of the
method of releasing Interatomic Energy,[2] a knowledge which in
the brain of an unscrupulous person would be most disastrous, not
only to himself but to those about him. The energy locked up in
an atom of matter is tremendous, and the release of this power is
only a matter of knowing the law. The inhabitants of your world
will have to bide a long time before the key that will release
this giant is placed within their reach.