We will now say something with respect to the geography of our
fellow-planet, a subject which seems all the more interesting because
Mars is so like the earth in many respects. We require a fairly
good telescope for the purpose of seeing him well, but when such an
instrument is directed to the planet, a beautiful picture of another
world is unfolded (Fig. 60). There are many things visible on his
surface, but we must always remember that even with our most powerful
telescopes the planet still appears a long way off.
[Illustration: FIG. 60.--Views of Mars.]
[Illustration: FIG. 61.--Mars.
(_By Douglass, Lowell Observatory._)]
In the most favorable circumstances, Mars is at least one hundred times
as far from us as the moon. But we know that an object on the moon must
be as large as St. Paul’s Cathedral if it is to be visible in our
telescopes. An object on Mars must be, therefore, at least one hundred
times as broad and one hundred times as long as St. Paul’s Cathedral if
it is to be discernible by astronomers on our earth. We can, therefore,
only expect to see the general features of our fellow-planet. Were we
looking at our earth from a similar distance, and with equally good
telescopes, the continents and oceans, and the larger seas and islands,
would all be large enough to be conspicuous. It is, however, doubtful
whether they could ever be properly revealed through the serious
impediment to vision which our atmosphere would offer.
It fortunately happens that the surface of Mars is only obscured
by clouds to a very trifling extent, and we are thus able to see a
panorama of our neighboring globe laid before us. Mars is not nearly
so large as our earth, the diameters of the two bodies being nearly
as two to one. It follows that the number of acres on the planet is
only a quarter of the number of acres on the earth. Careful telescopic
scrutiny shows that the chief features which we see on Mars are of a
permanent character. In this respect Mars is much more like the moon
than the sun. The latter presents to us merely glowing vapors, with
hardly more permanence than is possessed by the clouds in our own sky.
On the other hand, the entire absence of clouds from the moon enables
us to see the permanent features on its surface. Most of the visible
features on Mars are also invariable; though occasionally it would seem
that the climate produces some changes in its appearance.
[Illustration: FIG. 62.--The South Pole of Mars, September, 1877
(_Green_).]
We first notice that there are differently colored parts on Mars. The
darkish or bluish regions are usually spoken of as seas or oceans;
though we should be going beyond our strict knowledge were we to assert
that water is actually found there. Look at the horn-shaped object in
the centre of the lower picture in Fig. 60. We call it the Kaiser Sea,
and it is so strongly marked that even in a small telescope it can be
often seen. You must not, however, always expect to notice this feature
when you look at the planet through a telescope, for it turns round
and round. We can make a globe representing Mars. On this are to be
depicted this great sea and the other characteristic objects. But as
we turn the globe around, the opposite side of the planet is brought
into view, and other features are revealed like those represented in
the upper figure. Mars requires 24 hours 37 minutes 22.7 seconds to
complete a single rotation. It is somewhat remarkable that this only
differs from the earth’s period of rotation by a little more than half
an hour.
Mars contains what we call continents as well as oceans, and we also
find there lakes and seas and straits. These objects are indicated in
the drawings that are here represented. But the most striking features
which the planet displays are the marvellous white regions, which are
seen both at its North Pole and at its South Pole (Fig. 62). If we
were able to soar aloft above our earth and take a bird’s-eye view of
our own polar regions, we should see a white cap at the middle of the
arctic circle. This appearance would be produced by the eternal ice and
snow. It would increase during the long, dark winter, and be somewhat
reduced by melting during the continuously bright summer. Though we
cannot thus see our earth, yet we can sometimes observe one Pole of
Mars and sometimes the other, and we find each of these Poles crowned
with a dense white cap, which increases during the severity of its
winter, and which declines again with the warmth of the ensuing summer.
Sketches of Mars have been made by many astronomers; among them we may
mention Mr. Green, who made a beautiful series of pictures at Madeira
in 1877. These may be supplemented by the drawings of Mr. Knobel in
1884, when the opposite Pole of the planet was turned to view. The
drawings show the polar snows, and there seem to be some elevated
districts in his arctic regions which retain a little patch of snow
after the main body of the ice cap has shrunk within its summer limits.
An interesting case of this kind is shown in Fig. 62, which has been
copied from one of Mr. Green’s drawings.
It has lately been surmised that the continents on Mars are
occasionally inundated by floods of water. There are also indications
of clouds hanging over the Martian lands, but the inhabitants of
that planet, in this respect, escape much better than we do. A
certain amount of atmosphere always surrounds Mars, though it is much
less copious than that we have here. As to the composition of this
atmosphere we know nothing. For anything we can tell, it might be a
gas so poisonous that a single inspiration would be fatal to us; or if
it contained oxygen in much larger proportion than our air does, it
might be fatal from the mere excitement to our circulation which an
over-supply of stimulant would produce. I do not think it the least
likely that our existence could be supported on Mars, even if we could
get there. We also require certain conditions of climate, which would
probably be totally different from those we should find on Mars.
Many remarkable observations of Mars have been lately made by Mr.
Percival Lowell. It seems very doubtful how far our former division
of continents and oceans on Mars can be maintained. Mr. Lowell has
paid special attention to a wonderful system of lines on the planet’s
surface to which the name of “canals” has been given, which often show
such a degree of regularity as would almost suggest the idea that they
had been laid down by intelligent guidance.