Part 4

Other wonders of the sky were the round beacons of Jupiter’s other moons, three of which were about the same size as Callisto. They hung like bright searchlights in the starry heavens.

The men at the mining place greeted the Shannons warmly. They had not seen anyone from Earth for so long that they had grown very lonely.

The chief mining engineer said he would be glad to take the visitors on an underground tour. His name was Dr. Harding. He was plump and short and wore black-rimmed glasses inside his space helmet.

He led them into an elevator and it sank into the darkness. Steve remembered about the poisonous gases that crept about underground and it made him shiver to think about it.

Dr. Harding watched Bud hopping around uncomfortably inside his small space cage. “Do you remember, Mr. Shannon,” he asked over his suit radio, “when they used to use canary birds in mines to warn about leaking gas? The birds would notice it first and give the miners time to get out.”

“I’ve read about that, Dr. Harding,” said Mr. Shannon.

“Now we have automatic warning machines in the tunnels to do that,” the chief engineer told Sue and Steve.

Deeper and deeper below the soil of Callisto the elevator sank. At last the cage reached the bottom, and the riders found themselves in a large cavern. There were machines and men all about, working busily. Tracks led off into tunnels and ore cars were running on them. Some were going empty into the tunnels while others were coming out full of rock and gravel.

“The magna is separated from the rock in that big machine over there,” Dr. Harding explained. “Want to ride an ore car into one of the tunnels?”

“Sure!” Steve spoke up.

“The mine is air-conditioned,” the chief engineer said, “so we can take off our helmets.”

This done, Steve let Bud out of his cage. The little bird hopped up on his gloved finger, saying, “Rocket away!” several times. His two-word language seemed to do for everything.

One worker controlled all the cars at a main switch in the middle of the cavern. The Shannons and their guide climbed into an empty ore car and it rolled into a tunnel.

Glistening dark rock crowded in on Sue and Steve from all sides. Steve hoped the walls were strong enough so they would not come crashing down on their heads! There were lights along the way to help brighten the gloom.

After clicking along like a trolley for awhile, the car came to the end of the line. It was a large room with more machines and workmen. The men were digging magna ore out of the wall with drills.

As Dr. Harding explained about the work, Bud began flitting about as though sight-seeing on his own. He was shy of the workers at first, but then made friends with them. He spoke to them with his favorite two words and the men laughed in great fun to hear him.

Then a few minutes later, Bud began acting queerly. He flew back to Steve’s finger and started wobbling as though dizzy.

“What’s the matter with him?” Steve asked.

“He’s sick or something!” Sue cried out. She took the budgy from Steve and cuddled him in her own gloves. But the little blue bird seemed to be no better.

Dr. Harding walked over to look at the bird. Then he ordered, “Everybody into the ore car! We have to get out of here fast! Sue, hold the bird up close to your suit!”

The workers dropped their tools as if they were red hot and climbed into the car. Mr. Shannon helped Sue and Steve on, then jumped on himself.

Dr. Harding pressed the electric button that was the signal to the operator in the main cavern to move the car. The car began to roll down the track. It picked up speed as Dr. Harding kept pressing the button.

“Leaking gas, Dr. Harding?” Mr. Shannon asked worriedly.

The chief engineer nodded. He sniffed the air like a hunting dog after a scent. “Take a deep breath, everyone, then hold it!”

Steve thought his lungs would burst, but finally Dr. Harding let them take another deep breath. By the time they had taken one more, the car had reached the main cavern. As it rolled to a stop, Dr. Harding jumped down and ran over to the car operator.

Steve saw a door slide down and close off the tunnel where they had come out. Then the little man gave a deep sigh and took off his black-rimmed glasses to wipe them.

Sue and Steve watched Bud hopefully. He was standing more steadily on Sue’s finger now.

“I think he’ll be all right,” the chief engineer said. “We sure owe Bud a lot for warning us the way he did. Something must have happened to the warning machine. It was supposed to set off a siren.”

“If it weren’t for Bud we might have been overcome before we could have gotten out of there!” Mr. Shannon added.

“You’re so right!” Dr. Harding said. “The men will go back in there in gas masks to find the leak and see what’s wrong with the warning machine.”

“We’re plenty lucky!” Steve sighed, his spine still prickly from their narrow escape.

Sue kissed the budgy. “You’re a hero, Bud,” she told him, “and we love you!”

Bud blinked lazily. Then as if to show that he was all right again, he squawked, “Rocket away!”

_THE BIG SHOW ON TITAN_

The space freighter had landed on Titan, the largest moon in all the Solar System. The Shannon twins had been anxious to reach this moon of Saturn because their father had told them that something very exciting might happen here before they left.

There was still another reason why the children had looked forward to the landing. They would meet a boy of their own age who was the son of a worker. He had been living on Titan for the past two years and would be able to show them around.

Steve and Sue came down the outside “gangway” of the cargo ship and stepped onto the frozen ground of the distant world. The twins wore space suits, of course, for the air outside was extremely cold and it was poisonous as well with raw methane and ammonia.

Steve saw beautiful Saturn, with its colored rings, filling much of the blue sky. Titan was a world of close mountains, worn smooth by lots of windy weather. A film of glistening ice covered the peaks like caps of glass.

“Look up there, Sue!” Steve said. “Over our heads! That’s the famous skyport of Titan!”

“I wish we could go up there!” Sue said.

“Maybe we’ll get the chance,” answered Steve.

Ahead of them stood a rounded plastic dome. Men were carrying into it cartons of supplies which the space freighter had brought. The twins’ father, who was an official of the American Space Supply Company, was still aboard to take care of the unloading.

A boy came out of the domed building. “Are you the Shannons?” he asked over his space radio.

“Yes, we are,” Steve replied.

“I’m Bobby King.”

Sue and Steve said they were glad to meet him. He asked if they would like to go up and see the skyport.

Both the young Shannons answered a quick, “Sure!” together.

They followed their new friend into the plastic dome. Bobby King pointed to an overhead cable. Hanging from the heavy cord was a cable car.

“All aboard!” Bobby called, like a train conductor.

Sue and Steve giggled with pleasure as they entered the car, followed by Bobby. Bobby pushed a switch and the cable car began to move.

“We’re going up like a corkscrew,” Bobby said.

Round and round, right out of the top of the building, moved the cable car. Up and up it went. It took about ten minutes to reach the top. As soon as they got out, two men passed them who were talking about a storm that was on the way.

“Boy, if there’s a storm coming, you two are sure in luck!” Bobby told Sue and Steve.

Steve and Sue looked at one another, puzzled. Why should their young friend be pleased over a coming storm?

They saw before them a space that looked as flat as a highway and larger than a football field. There was a row of hangars along the far side.

“Wow, we sure must be high!” Steve burst out. They seemed to be almost on a level with the mountains.

“We’re a whole mile off the ground,” Bobby told him. “The skyport rests on the corners of two mountain ridges.”

They went over to one of the clear plastic walls that edged the skyport.

“Gee, the freighter sure is little down there!” Sue said.

It almost took Steve’s breath away. The big space ship indeed looked no larger than a toy down below.

“Why did they go to such trouble to build this?” Steve asked.

“Because there wasn’t any place flat enough on the ground,” Bobby answered. “My father says they need a main skyport on Titan because there are so many companies here digging for uranium. The colonists fly here to get their supplies and mail.”

“I see some dark clouds over the mountains,” Sue said. “Does that mean a storm is coming?”

Bobby’s helmet nodded. “It sure does! You two are the luckiest ones! You got here right at the start of the storm season.”

Steve and Sue were still puzzled as to why Bobby wanted it to storm.

Bobby showed his guests a faint star burning through the blue atmosphere. “That’s Earth,” he told them, “750 million miles away. My father thinks we can go back for a visit in a few weeks. I’ll be glad.”

“Where do you live here, Bobby?” Sue asked.

“My father and I stay in an apartment a little way from here,” Bobby answered.

“How about school?” Steve wanted to know. “Do they have one on Titan?”

Bobby shook his head. “My father teaches me. He’s out with some prospectors today.”

Bobby showed them Titan’s other nine sister moons, which looked like glowing fireballs. Steve saw that most of the daylight came from Saturn because the sun was so far away. It wasn’t nearly as bright here as it was on Earth.

“I wish we could run over to Saturn for a visit,” Sue said, jokingly.

“You don’t really, Sue,” Bobby told her. “You couldn’t stand up in its heavy gravity. Saturn’s almost as big as Jupiter, you know.”

“What are Saturn’s rings made of?” Steve asked.

“Oodles and oodles of rocks,” Bobby replied. “They are traveling so fast that they make the rings look like one solid piece.”

Wind was beginning to howl around them and this seemed to make Bobby very excited.

The coming storm must be something special, Steve thought. His curiosity had been aroused strongly.

The clouds gathered darker and more thickly behind the mountains. The wind was driving harder.

“Hadn’t we better go inside?” Sue asked, worriedly.

“Shucks, no!” Bobby said. “It won’t be any fun unless we’re right out in it! There won’t be any rain. It’s too cold on Titan for rain.”

Suddenly the three heard a loud siren wail.

“That means a jet plane is coming in,” Bobby said. “All planes have to land when word of a storm gets around.”

The plane’s wheels touched down and the ship rolled along until a hook on it caught a line that stretched across the runway. The line brought the plane to a sharp halt.

The jet’s wings were folded down and the ship was pushed off to a hangar. Two more ships landed afterward. Then a blinding flash lighted up the sky. It made Steve and Sue blink and jump in fright.

“Look!” Bobby exclaimed. “The storm has begun!”

Other men had come out to see what was going to happen and they lined up along the edges of the skyport with the children.

Bobby pointed to a sparkling balloon of light that burst into a blossom of sparks over the mountains. A moment later a red dagger flash skipped across the peaks. During all this there were loud crashes and rumblings. Steve was scared and thrilled at the same time.

“It’s just like fireworks!” Sue called out.

Now Steve could understand why Bobby had looked forward to the storm. He guessed, too, that this was the exciting surprise their father had said might happen while they were here.

An orange pinwheel, like a Fourth of July sparkler, rose from a mountain top and looped upward. It grew bigger and bigger and fainter and fainter at the same time. It was really a beauty.

“What causes the fireworks?” Steve asked above the noise.

“Partly strong wind,” Bobby said loudly, “and partly Titan’s gases exploding against the mountain tops!”

They watched spellbound for fifteen minutes, then a half hour. The Shannons were sure they had never seen anything quite so breathtaking as this.

At one time a row of peaks seemed to glow with a sheet of red flame. The flame danced and flickered like a forest fire for a long time before it faded out.

The children had been enjoying themselves so thoroughly that they knew nothing of the peril that was heading their way.

The first warning came when one of the skyport men standing nearby shouted over his space suit radio. Steve whirled in alarm. His heart seemed to stop beating completely for a terrible moment.

A tardy plane had come in for a landing on the sky platform. But the howling wind had kept everyone from hearing the warning siren.

Because of the fierce blowing, the plane had not hooked firmly to the braking line. It scooted off to the side and was heading for the very spot where Bobby, Steve and Sue stood.

“Bobby!” Steve cried. “Get out of the way!” As Bobby ducked for safety, Steve also moved quickly. Sue screamed as Bobby grabbed her hastily by her space glove. He had to jerk her sharply in order to get her out of the path of the runaway plane.

The plane crashed into the plastic wall of the skyport, tearing out a section of wall as though it were thin cardboard. The ship was left dangling on the very edge as if ready to fall a mile to the ground.

“The poor pilot!” Sue cried. “Oh, I can’t look!”

But the skyport men had come running quickly over and together they pulled the jet plane back to safety. They helped the scared pilot out. He walked shakily off into one of the hangars.

“Whew! That was close!” Steve breathed. “For him and us, too!”

“My heart is still thumping like a drum!” Bobby said.

As for Sue, she was too upset to say anything at all.

They turned to look at the fireworks to take their minds off the accident. The wonderful ending of the show almost made them forget it completely.

They saw a dazzling white light burst like an empty volcano. The banner of fire rose as high into the sky as huge Saturn. Then it spilled over like a great fountain. It changed into purple, then blue, green and red.

Before dying out, it gave the big planet a lovely ruddy glow, showing up its rings like a gleaming necklace of rubies. That was the end of Nature’s grand performance.

“Wow, wasn’t that terrific?” Steve asked. “A show like that in a grandstand on Earth would cost you three-and-a-half.”

“Maybe four!” Sue chimed in.

“You can’t see this show anywhere on Earth, Steve,” Bobby said. “Titan is the only place. And the good thing about it is that it’s all for free!”

_ADVENTURE ON THE SUN’S DOORSTEP_

Sue and Steve Shannon watched the magic world of stardust through a port of the rocket freighter. The ship was moving under power of its atomic engines, headed toward the sun.

They had one more cargo stop to make before returning to their beloved soil on the Earth.

The twins heard the clack of magnetic soles behind them. Without such shoes holding them to the floor, space travelers would float about helplessly like wingless birds.

“Hi, kids,” greeted their father. “Growing tired of the view?”

“I guess I am, Dad,” Steve admitted. His blue eyes were tired.

“How far away is Apollo’s Chariot now?” Sue asked.

Mr. Shannon grinned. “That’s the umpteenth time you two have asked that. But I suppose I’m as restless as you are to get back to Mom in Arkansas.”

Hearing this made Steve suddenly homesick. There was really no place like home, just like the poet had said. Steve knew Sue felt the same way. He had seen a wistful look in her hazel eyes every time they had talked of Little Rock.

The seemingly endless days finally did end. The three Shannons went up into the lookout dome with the crewmen. The dome was covered by a darkened plastic screen to cut down the blinding glare of the sun, which was very close.

It was a heart-stopping sight for Sue and Steve. The planet Mercury covered the face of the sun like a black plate. Streaming out from the edges were mountainous tongues of living fire. Mr. Shannon called this flaming halo the sun’s _chromosphere_.

“Gee, what a thing to see!” Steve gasped.

“It’s—it’s unbelievable!” Sue added, breathless.

“Indeed, it is,” Mr. Shannon agreed. “See that thing like a lighted wheel just ahead of us? That’s Apollo’s Chariot. It was named after the famous Greek sun god, you know.”

Sue and Steve knew that Apollo’s Chariot was really a space laboratory that was a home for scientists who were studying the sun. They had been the ones who had given their tiny world its colorful nickname. It was protected with asbestos and other special material to shield it from the heat as it circled the great star, month after month, year after year.

“We had to contact Apollo’s Chariot while Mercury was shading our ship from the sun’s rays,” Mr. Shannon said. “We aren’t protected like Apollo’s Chariot is.”

“Mercury seems as big as the sun, the way it covers it completely,” Steve remarked.

“That’s because we’re so close to Mercury,” his father explained. “Actually, the sun is so much bigger it’s like comparing a pinpoint to a grapefruit!”

In the midnight darkness between the ships, giant searchlights had to be turned on. Then the scientists on the other ship came out onto their loading platform to receive their cargo. Conversation was carried on by means of space suit radios with those aboard the freighter, who stood on their own outside platform.

“Why can’t we get closer to Apollo’s Chariot?” Steve asked Biff Warren, who was the twins’ favorite among the crewmen. Biff was piling boxes and crates at the edge of the platform.

“Space regulations,” answered Biff. “If a meteor should hit one of us, the other ship would explode too if we were close. Also, rocket tubes are so tricky that you never know when one is going to misfire and send your ship scooting off suddenly in the wrong direction.”

One end of a double cable was fastened to rings on the freighter’s platform. Then the other end was tossed across the space between the two ships and attached by the scientists to their own side.

Steve saw the crewmen around him pick up cords from out of the cable equipment box. They fastened one end to buckles on their suits and the other to the cable. Steve guessed that the lines were a safety measure to keep the men from drifting off into space as they carried the cargo across.

The first crewman picked up a crate as lightly as if it were a pile of feathers. Then with his foot he shoved off from the platform.

He guided the crate through the emptiness with his gloved hands and the men on the opposite platform helped him aboard. Another crewman stepped off the freighter with another crate. Then another crewman with another piece of cargo. The carriers returned by the other cable line.

Steve went over to his dad who, as an official of the American Space Supply Company, was supervising the work as always. “Dad, may Sue and I carry a box across? We’ll be careful.”

Mr. Shannon thought a moment. “I suppose it will be all right. There’s no way you can go adrift if you fasten on to the cable. But you have to be careful you’re snapped on securely.”

Mr. Shannon made a place for them in line. Sue in front. There was a wait before Sue’s turn so that more crates could be placed on the platform’s edge. The children looked beyond Apollo’s Chariot at the huge black circle of Mercury as it masked the mighty sun.

“Biff,” Steve asked his friend as he was stacking the crates, “why couldn’t the Apollo scientists study the sun from Mercury?”

Biff chuckled and it made a funny crackling sound over the young Shannons’ radios. “Men will land on Mercury when they grow hides of asbestos, Steve. It’s so hot on the sunward side that there are supposed to be lakes and pools of lead there! The other side never sees the sun, so you can imagine how cold it is! Think you two would like to go there?”

“I should say not!” Sue answered for both of them.

When the next piece of cargo was ready to go over, Biff checked the children’s safety cords. Then he let Sue push off from the platform with a box in front of her. A few moments later, Steve followed. The boy heard his sister giggle excitedly as they floated across. Searchlight beams were in their eyes but they didn’t mind. Steve, too, thought this great fun after being cramped for so long on the freighter. He looked down at the empty space below, but he knew he could not fall and so was not afraid. Reaching the other platform, he and his sister were helped aboard.

“They sure are using young crewmen these days!” joked one of the scientists, a tall man who seemed to be working harder than the others. “Nice work, young folks!”

The scientist was in the act of changing the children’s cords over to the returning cable when a slight mishap occurred. One of the crates coming over bumped into him. He laughed as he again got to his feet but his laughter quickly changed to alarm when Sue suddenly pushed off from the platform. She had thought her cable line was secure and that she was ready to make the exciting trip back across the gulf.

“Wait, miss!” the scientist called. “I didn’t finish fastening your cable cord!” He reached for Sue but her suit slipped out of the fingers of his bulky space gloves.

Steve froze for an instant in terror at what he had seen. Then without thought of anything else except his sister’s danger, he dove right off the platform after Sue, not realizing or caring that his own cable cord was not fastened.

If the scientist had not grabbed for Sue she might have floated safely across to the freighter. But by touching her he had sent her off in a direction beneath it.

Over his radio, Steve heard her screaming for help and saw her flinging her arms and legs about like a drowning swimmer. Steve was moving faster than she and presently caught up with her.

“What are we going to do, Steve?” she cried, holding tightly to him. “We can’t stop! And it’s so dark out here!”

Steve knew that unless someone came to their aid they would drift on and on since there was no air to slow them down. But he didn’t tell Sue this.

He remembered, as he had at times before, that a spaceman must keep his head in an emergency. He spoke comforting words to Sue, telling her to try to be calm, that help would be coming.

Even as he told her this a spear of light hit them and a voice broke in on their radio: “Steve! Sue! Stop struggling! I’m on my way to you!”

“Biff!” Steve exclaimed, and the dread in his heart suddenly lifted. He looked over his shoulder and saw their big friend approaching, guided by the light that had been flashed on them from the freighter.

There was a little plume of flame trailing behind him. In a few minutes he had caught up with them. Sue was so glad to see him she grabbed the big spaceman and her helmet bumped against his in an attempted kiss.

“Oh, I’m so glad to see you, Biff!” she sobbed. “I was so _awfully_ scared!”

“You’re all right now,” Biff said gently. “Both of you hold on to me and we’ll go back.”

Steve took Biff’s left arm and Sue firmly grasped one of Steve’s. Biff carried a type of hand rocket, called a “pusher,” that he had used to shoot himself along toward them. By pointing the rocket in the opposite direction from which he wanted to go, the “pusher” pushed him in the manner of the rocket tubes on the freighter.

Biff pointed the pusher away from the freighter. Steve saw a burst of fire beside them and the three of them sped off toward the big ship. As Sue reached the platform, her father was there to help her aboard. She could see in his eyes the fear he had felt for them.

Steve was surprised to have the crew greet him warmly with pats on the back. The boy turned to his father. “Why are they calling me a hero?” he asked. “It was Biff who saved us!”