But with all his variations in brilliancy and beauty Mars remains ever a charming, rosy-hued planet, shining always with a steady, clear light, and when once we have come to know him is not easily mistaken for any other planet, or for any of the brilliant stars that may more or less resemble him in color. Red in varying degrees of intensity is, perhaps, the most obviously distinguishing mark of Mars; but his own characteristics are never more distinct than when his path takes him into the region of the two best-known red stars in the heavens. These are Antares, the glowing star in the constellation Scorpio, which we see in the southern sky during the summer, and ruddy Aldebaran, which shines in the head of Taurus and under the Pleiades through the bright wintry nights. On every journey around the skies Mars passes near these two stars. They are both in the constellations of the zodiac, and are often quite near to Mars, as well as to the other planets and the moon. The stars, though of the same color as Mars, are much more jewel-like than the planet. Mars is less sparkling. When it is small, it shows a placid, rosy little disc, without much gaiety, and not in any way suggesting anything martial; but at its largest, it has a distinctly flame-like aspect, which easily suggests why it was named for the god of war. [Illustration: THE TWO PHASES OF MARS We see its full face when it is opposite the sun. When half-way between opposition and conjunction it becomes gibbous, as shown in the photograph on the right. These photographs were made at the Mt. Wilson Observatory.] Mercury is the only planet that in color even suggests Mars, and for Mercury it can never be mistaken after one has once seen the two planets. Mercury, we know, is always very near the sun; but when visible at all is, even in that unfavorable situation, always as bright as a first-magnitude star. Mars is near the sun, to our view, only when it is approaching conjunction, and it is then so far from us that it always appears as a rather small star, and, while never insignificant, is, in this situation, quite inconspicuous even as compared with the rarely visible Mercury. On seeing a planet, then, sufficiently high above the horizon to attract one’s attention, one may be sure that it is Mars if it is red, and equally sure that it is not Mars if it does not show this color. Under certain atmospheric conditions the sun, moon, and all the planets sometimes appear red when they are very near the horizon; but in this situation there is always something other than color that marks them.