The Planet Venus

The planet Venus, the bright globe which is known to all as the morning and evening "star," seems at first sight more promising as regards the possibility of life. It is of nearly the same size as the earth, and it has a good atmosphere, but there are many astronomers who believe that, like Mercury, it always presents the same face to the sun, and it would therefore have the same disadvantage—a broiling heat on the sunny side and the cold of space on the opposite side. We are not sure. The surface of Venus is so bright—the light of the sun is reflected to us by such dense masses of cloud and dust—that it is difficult to trace any permanent markings on it, and thus ascertain how long it takes to rotate on its axis. Many astronomers believe that they have succeeded, and that the planet always turns the same face to the sun. If it does, we can hardly conceive of life on its surface, in spite of the cloud-screen.

FIG. 14.—THE MOON

Showing a great plain and some typical craters. There are thousands of these craters, and some theories of their origin are explained on page 34.

FIG. 15.—MARS

1} Drawings by Prof. Lowell to accompany actual photographs of Mars showing many of the
2} canals. Taken in 1907 by Mr. E. C. Slipher of the Lowell Observatory.
3 Drawing by Prof. Lowell made January 6, 1914.
4 Drawing by Prof. Lowell made January 21, 1914.
Nos. 1 and 2 show the effect of the planet's rotation. Nos. 3 and 4 depict quite different sections. Note the change in the polar snow-caps in the last two.

FIG. 16.—THE MOON, AT NINE AND THREE-QUARTER DAYS

Note the mysterious "rays" diverging from the almost perfectly circular craters indicated by the arrows (Tycho, upper; Copernicus, lower), and also the mountains to the right with the lunar dawn breaking on them.

We turn to Mars; and we must first make it clear why there is so much speculation about life on Mars, and why it is supposed that, if there is life on Mars, it must be more advanced than life on the earth.