The Secret of the Ninth Planet

by Donald A. Wollheim

Clyde's face, which had been tense, was now more relaxed. "I think we've got the problem licked," came the good word.

"What's up?" asked Burl. "If we shoot past Venus, we should still be able to come to a stop, fall away from the Sun and maybe catch up with Venus again. It would take longer, but...."

"We're altering our plans," interrupted Russ. "Of course, we could brake—that much we found out for sure. The trouble lay in our lack of effective tests for the Magellan's drive. We thought we knew just what it would do, but after all, the problems of space are intricate. It turned out that it did not act so effectively against the Sun as had been calculated. Either that, or the Sun's pull was stronger at this proximity than registered on our instruments. Chasing after Venus, after coming back to its orbit, could be done, but it would prove time-consuming and difficult to plan. What we are doing instead is altering our schedule."

"But then there's no other place to go from here but Mercury. Is that what the new plan is?" Burl asked him.

Russ nodded. "Mercury is coming around this side of the Sun. By the time we have braked, we will be closer to its orbit than to that of Venus. So we shall proceed inward toward it and make our first planetfall there."

Mercury, the smallest and hottest planet in the system. Burl remembered that it was one of the two worlds that they knew for sure had a Sun-tap station on it. He went down the hatch to carry the news to the landing crew.

Haines, Burl discovered, had already heard the new plan on the intercom from Lockhart. As soon as Burl joined them, the four men, including Ferrati and Boulton, went into a planning session.

The problem of Mercury was a hard one. As Ferrati remarked, "It would have been better to tackle this one last instead of taking it on first."

"Yes, but on the other hand," was Haines's comment, "Mercury's station is probably one of the most important—located as it is, so close to the Sun. With ideal conditions for steady, undiverted concentration of solar power, it must be the primary station in the system."

"The problem boils down—and I do mean 'boils'—to heat," Boulton laughed. "Mercury rotates on its axis only once a year—its year being only eighty-eight of our days long. This means that just as the Moon presents only one side to the Earth, Mercury always presents the same hemisphere to the Sun. On the Sun side, therefore, there is always day. The Sun appears to be fixed in the sky. Naturally, we assume the Sun-tap station will be on that sunny side. And the heat must be terrific."