"We must be doing fully a million," replied Cortlandt, "for by this time we are pretty well in motion, having got a tremendous start when so near the moon, with it and the earth in line."
By steering straight for Jupiter, instead of for the place it would occupy ten days later, they knew they would swing past, for the giant planet, being in rapid motion, would advance; but they did not object to this, since it would give them a chance to examine their new world in case they wished to do so before alighting; while, if they preferred to land at once, they could easily change their course by means of the moons, the fourth, from which their car was named, being the one that they knew would be of most use. Their tremendous speed showed them they should have time for exploration on their arrival, and that they would reach their destination sooner than they had expected. The apergetic force being applied, as we have seen, only to the Callisto, just as power in starting is exerted on a carriage or railway car and only through it to the passengers, Ayrault and his companions had no unusual sensation except loss of weight, for, when they were so far from the earth, its attraction was very slight, and no other planet was near enough to take its place. After breakfast, wishing to reach the dome, and realizing that it would be unnecessary to climb, each in turn gave a slight spring and was obliged to put up his hands to avoid striking the roof. In the cool quiet of the dark dome it was difficult to believe that only twenty feet away the sun was shining with such intensity upon the metal base as to make it too hot on the inside to touch without gloves.
The first thing that attracted their attention was the size and brilliance of Mars. Although this red planet was over forty million miles from the earth when they started, they calculated that it was less than thirty million miles from them now, or five millions nearer than it had ever been to them before. This reduction in distance, and the clearness of the void through which they saw it, made it a splendid sight, its disk showing clearly. From hour to hour its size and brightness increased, till towards evening it looked like a small, full moon, the sun shining squarely upon it. They calculated that on the course they were moving they should pass about nine hundred thousand miles to the right or behind it, since it was moving towards their left. They were interested to see what effect the mass of Mars would have on the Callisto, and saw here a chance of still further increasing their speed. Notwithstanding its tremendous rate, they expected to see the Callisto swerve from its straight line and move towards Mars, whose orbital speed of nine hundred miles a minute they thought would take it out of the Callisto's way, so that no actual collision would occur even if their air-ship were left to her own devices.
Towards evening they noticed through their glasses that several apparently island peaks in the southern hemisphere, which was turned towards them, became white, from which they concluded that a snow-storm was in progress. The south polar region was also markedly glaciated, though the icecap was not as extensive as either of those at the poles of the earth.
"As the Martian winters must be fully as severe as ours," said Cortlandt, "on account of their length, the planet's distance from the sun, and the twenty-seven and a half degrees inclination of its axis, we can account for the smallness of its ice-caps only by the fact that its oceans cover but one fourth of its surface instead of three quarters, as on the earth, and there is consequently a smaller evaporation and rain and snow-fall."
They were too much interested to think of sleeping that night, and so, after dining comfortably returned to their observatory. When within four million miles of Mars the Callisto began to swerve perceptibly, its curve, as when near the moon beginning with a spiral. They swung on unconcernedly, however, knowing they could check their approach at any time. Soon Mars appeared to have a diameter ten times as great as that of the moon, and promised shortly to occupy almost one side of their sky. "We must be on the lookout for the satellites," said Cortlandt; "a collision with either would be worse than a wreck on a desert island."
They therefore turned their glasses in the direction of the satellites.
"Until Prof. Hall, at Washington, discovered the two satellites in 1877," he continued, "Mars was supposed to be without moons. The outer one, Deimos, is but six miles in diameter, and revolves about its primary in thirty hours and eighteen minutes, at a distance of fourteen thousand six hundred miles. As it takes but little longer to complete a revolution than Mars does to rotate on its axis, it remains in the Martial sky one hundred and thirty-two hours between rising and setting, passing through all the phases from new moon to full and back again four times; that is, it swings four times around Mars before going below the horizon. It is one of the smallest bodies discovered with a telescope. The inner one, Phobos, is considerably larger, having a diameter of about twenty miles. It is but twenty-seven hundred miles from Mars's surface, and completes its revolution in seven hours and thirty-eight minutes, which is shorter than any other known period, Jupiter's nearest moon being the next, with eleven hours and fifty-nine minutes. It thus revolves in less than a third of the time Mars takes to rotate, and must consequently rise in the west and set in the east, as it is continually running ahead of the surface of the planet, though the sun and all the other stars rise and set on Mars in the same way as on the earth."
When about fifteen thousand miles from Mars, they sighted Deimos directly ahead, and saw that they should pass on its left--i. e., behind--for it was moving across them. The sun poured directly upon it, making it appear full and showing all its features. There were small unevennesses on the surface, apparently seventy or a hundred feet high, which were the nearest approach to mountains, and they ran in ridges or chains. There were also unmistakable signs of volcanic action, the craters being large compared with the size of the planet, but shallow. They saw no signs of water, and the blackness of the shadows convinced them there was no air. They secured two instantaneous photographs of the little satellite as the Callisto swept by, and resumed their inspection of Mars. They noticed red and brownish patches on the peaks that had that morning turned white, from which they concluded that the snow had begun to melt under the warm spring sun. This strengthened the belief they had already formed, that on account of its twenty-seven and a half degrees inclination the changes in temperature on Mars must be great and sudden. So interested were they with this, that they did not at first see a large and bright body moving rapidly on a course that converged with theirs.
"We must be ready to repel boarders," said Bearwarden, observing it for the first time and fixing his glass upon it. "That must be Phobos."