"That's just it," said Astro. "I'm not mistaken! Those jokers must have changed over from chemical fuel to reactant drive!"
"But why?" asked Roger. "That would cost more than they could make in ten years of hauling passengers on joy rides!"
Astro whirled around and faced the two cadets. "I'm telling you the ship that blasted off from here was an atomic drive. I don't know any more than that, but I do know that!"
There was a sudden shout from Strong and the three boys hurried to the shack. The Solar Guard captain and the exposition commissioner were standing inside and playing the beam of an electric torch around the walls.
"Looks as though you were right about the atomic drive, Astro," said Strong. He flashed the light into one corner where a tangled jumble of lines lay on the floor. "That's feed-line gear for a chemical burner, and over there"—he played the light on some empty cartons—"is what's left of the crate's lead baffling it shipped in. They must have changed over to atomic drive recently."
Astro accepted the statement with a nod. It wasn't in the nature of the big cadet to boast. Now that the secret of the ship had been resolved, he turned, like the others, to the question of why?
"I think the best thing we can do," said Strong, "is to spread out and search the whole area. Might find something to indicate where they went." Commissioner Hawks nodded his head in agreement.
While Tom, Roger, and Astro searched outside, Strong and Hawks went through the drawers of the dusty desk standing in one corner.
"Nothing here but a record of the flights they made, bills for chemical fuel delivered, and the like," said Hawks at last. "They were losing money on the operation, too. Think they might have just gotten fed up and pulled out?"
Strong was rummaging around in one corner of the shack. "I'd go along with that, but for one thing, Mike," he said. "Take a look at this." He held up a small cloth bag. "There's dirt in the bottom of this bag. And there are about fifty more bags in that corner."