on the commissioner’s desk. Hawks watched him carefully as he studied the papers.
“You say this is the ninth report you’ve received since the fair opened, Mike?” asked Strong finally.
Hawks nodded. He hadn’t known whether to laugh off or seriously consider the nine space skippers’ reports that the sky over the exposition site was dirty.
“Yes, Steve,” he said. “That one came from the skipper of an express freighter. He blasted off this morning and ran through this so-called dirt. He thought it was just a freak of nature but reported it to be on the safe side.”
“I don’t suppose he took a sample of the stuff?”
“No. But I’m taking care of that,” replied Hawks. “There’s a rocket scout standing by right now. Want to come along?”
“Let me finish these reports first.”
“Sure thing.”
As Strong carefully checked each report, Commissioner Hawks rose and began to stride restlessly back and forth across the spacious office. He stopped in front of the window and stared out over the exposition grounds, watching the thousands of holiday visitors streaming in and out of the buildings, all unaware of the strange mystery in the sky above them. Hawks’ attention was drawn to the giant solar beacon, a huge light that flashed straight out into space, changing color every second and sending out the message: “Quis separabit homo”—Who shall separate mankind?
This beacon that at the beginning of the exposition had reached into the black void of space like a clean bright ray was now cloudy and murky—the result of the puzzling “dirty sky.”
“All right, Mike,” Strong announced suddenly. “Let’s go.”
“Get anything more out of those reports?” asked Hawks, turning back to his desk.
“No,” replied the Solar Guard officer. “They all tell the same story. Right after blast-off, the ships ran into a dirty sky.”
“Sounds kind of crazy, doesn’t it?”
“Crazy enough to check.”
Hawks pressed a button on the desk intercom.
“Yes, sir?” replied a metallic voice.
“Have the rocket scout ready for flight in five minutes,” Hawks ordered. He snapped off the intercom without waiting for a reply and turned to Strong. “Let’s go, Steve.”
The two veteran spacemen left the office without further comment and rode down in the vacuum elevator to the highway level. Soon they were speeding out to the spaceport in Hawks’ special jet car.
At the blast-pitted field they were met by a young Solar Guard officer and an elderly man carrying a leather case, who were introduced as Lieutenant Claude and Professor Newton.
While Claude prepared the rocket scout for blast-off, Strong, Hawks, and Newton discussed the possibility of lava dust having risen to great heights from another side of the planet.
“While I’m reasonably sure,” stated Newton, “that no volcano has erupted recently here on Venus, I can’t be sure until I’ve examined samples of this so-called dirt.”
“I’ll have Lieutenant Claude contact the University of Venus,” said Hawks. “Their seismographs would pick up surface activity.”
Claude stuck his head out of the hatch and reported the ship ready for blast-off. Strong followed the professor and Hawks aboard and strapped himself into an acceleration chair. In a moment they were blasting through the misty atmosphere of Venus into the depths of space.
Fifteen minutes later, Hawks and Strong were standing on the hull of the ship in space suits, watching the professor take a sample of a dirty black cloud, so thick it was impossible to see more than three feet. Strong called to the professor through the spacephone.
“What do you make of it, sir?” he asked.
“I wouldn’t want to give you a positive opinion without chemical tests,” answered the professor, his voice echoing in Strong’s fish-bowl helmet. “But I believe it’s one of three things. One, the remains of a large asteroid that has broken up. Two, volcanic ash, either from Venus or from Jupiter. But if it came from Jupiter, I don’t see how it could have drifted this far without being detected on radar.”
Now, holding a flask full of the black cloud, the professor started back to the air lock.
“You said three possibilities, professor,” said Strong.
“The third,” replied the professor, “could be—”
The professor was interrupted by Lieutenant Claude calling over the intercom.
“Just received a report from the University of Venus, sir!” said the young officer. “There’s been no volcanic activity on Venus in the last ten years serious enough to create such a cloud.”
Strong waited for the professor’s reaction, but the elderly man was already entering the air lock. Before Strong and Hawks could catch up to him, the air-lock hatch slammed closed.
“Hey,” exclaimed Strong, “what does he think he’s doing?”
“Don’t worry about it, Steve,” replied Hawks. “He probably forgot we were out here with him, he’s so concerned about this dirt. We’ll just have to wait until he’s out of the air lock.”
The Solar Guard officer nodded, then looked around him at the thick black cloud that enveloped the ship. “Well,” he said, “one of the professor’s theories has been knocked out.”
“Yes,” replied Hawks. “Which means this stuff is either the remains of a large asteroid or—”
“The third possibility,” finished Strong, “which the professor never explained.”
Suddenly the air-lock hatch opened again and the two spacemen stepped inside. Closing the hatch behind them, they waited until the pressure was built up again to equal that of the ship, and then they removed their helmets and space suits.
Leaving the air lock and walking down the companionway, Hawks suddenly caught Strong by the arm.
“Have you considered the possibility of this cloud being radioactive, Steve?” he asked.
Strong nodded slowly. “That’s all I’ve been thinking about since I first heard about it, Mike. I think I’d better report this to Commander Walters at Space Academy.”
“Wait, Steve,” said Hawks. “If you do that, Walters might close the exposition. Wait until you get a definite opinion from Professor Newton.”
Strong considered a moment. “I guess a few more minutes won’t make a lot of difference,” he said finally. He realized how important the exposition was to his old friend. But at the same time, he knew what would happen if a radioactive cloud suddenly settled on the city of Venusport without warning. “Come on. Let’s see what the professor has to say about this stuff.”
They found the professor on the control deck bending over a microscope, studying samples taken from the flask. He peered intently into the eyepiece, wrote something on a pad, and then began searching through the pages of a reference book on chemicals of the solar system.
Lieutenant Claude stepped up to Hawks and saluted sharply. “Power deck reports they’ve got a clogged line, sir. It’s in the gas exhaust.”
Strong and Hawks looked at each other, and then Hawks turned to the young officer. “Send a couple of men outside to clear it.”
“Aye, aye, sir,” said Claude, and then hesitated. “Shall the men wear lead suits against possible radioactivity, sir?”
Before Hawks could answer, Newton turned to face the three men. The professor was smiling. “No need to take that precaution, Lieutenant. I never did tell you my third opinion, did I, Captain Strong?”
“Why,