'Mail ship,' Preston said. 'From Earth. What's going on?'
There was the sound of voices whispering somewhere near the microphone. Finally: 'Hello, Mail Ship?'
'Yeah?'
'You're going to have to turn back to Earth, fellow. You can't land here. It's rough on us, missing a mail trip, but—'
Preston said impatiently, 'Why can't I land? What the devil's going on down there?'
'We've been invaded,' the tired voice said. 'The colony's been completely surrounded by iceworms.'
'Iceworms?'
'The local native life,' the colonist explained. 'They're about thirty feet long, a foot wide, and mostly mouth. There's a ring of them about a hundred yards wide surrounding the Dome. They can't get in and we can't get out— and we can't figure out any possible approach for you.'
'Pretty,' Preston said. 'But why didn't the things bother you while you were building your Dome?'
'Apparently they have a very long hibernation-cycle. We've only been here two years, you know. The iceworms must all have been asleep when we came. But they came swarming out of the ice by the hundreds last month.'
'How come Earth doesn't know?'
'The antenna for our long-range transmitter was outside the Dome. One of the worms came by and chewed the antenna right off. All we've got left is this short-range thing we're using and it's no good more than ten thousand miles from here. You're the first one who's been this close since it happened.'
'I get it.' Preston closed his eyes for a second, trying to think things out.
The Colony was under blockade by hostile alien life, thereby making it impossible for him to deliver the mail. Okay. If he'd been a regular member of the Postal Service, he'd have given it up as a bad job and gone back to Earth to report the difficulty.
'Give me a landing orbit anyway, Ganymede.'
'But you can't come down! How will you leave your ship?'
'Don't worry about that,' Preston said calmly.
'We have to worry! We don't dare open the Dome, with those creatures outside. You
'You want your mail or don't you?'
The colonist paused. 'Well—'
'Okay, then,' Preston said. 'Shut up and give me landing coordinates!'
There was a pause, and then the figures started coming over. Preston jotted them down on a scratch- pad.
'Okay, I've got them. Now sit tight and wait.' He glanced contemptuously at the three mail-pouches behind him, grinned, and started setting up the orbit.
He brought the Postal Ship down with all the skill of his years in the Patrol, spiralling in around the big satellite of Jupiter as cautiously and as precisely as if he were zeroing in on a pirate lair in the asteroid belt. In its own way, this was as dangerous, perhaps even more so.
Preston guided the ship into an ever-narrowing orbit, which he stabilized about a hundred miles over the surface of Ganymede. As his ship swung around the moon's poles in its tight orbit, he began to figure some fuel computations.
His scratch-pad began to fill with notations.
Finally he looked up. He had computed exactly how much spare fuel he had, how much he could afford to waste. It was a small figure—too small, perhaps.
He turned to the radio. 'Ganymede?'
'Where are you, Postal Ship?'
'I'm in a tight orbit about a hundred miles up,' Preston said. 'Give me the figures on the circumference of your Dome, Ganymede?'
'Seven miles,' the colonist said. 'What are you planning to do?'
Preston didn't answer. He broke contact and scribbled some more figures. Seven miles of iceworms, eh? That was too much to handle. He had planned on dropping flaming fuel on them and burning them out, but he couldn't do it that way.
He'd have to try a different tactic.
Down below, he could see the blue-white ammonia ice that was the frozen atmosphere of Ganymede. Shimmering gently amid the whiteness was the transparent yellow of the Dome beneath whose curved walls lived the Ganymede Colony. Even forewarned, Preston shuddered. Surrounding the Dome was a living, writhing belt of giant worms.
'Lovely,' he said. 'Just lovely.'
Getting up, he clambered over the mail sacks and headed toward the rear of the ship, hunting for the auxiliary fuel-tanks.
Working rapidly, he lugged one out and strapped it into an empty gun turret, making sure he could get it loose again when he'd need it.
He wiped away sweat and checked the angle at which the fuel-tank would face the ground when he came down for a landing. Satisfied, he knocked a hole in the side of the fuel-tank.
'Okay, Ganymede,' he radioed. 'I'm coming down.'
He blasted loose from the tight orbit and rocked the ship down on manual. The forbidding surface of Ganymede grew closer and closer. Now he could see the iceworms plainly.
Hideous, thick creatures, lying coiled in masses around the Dome. Preston checked his spacesuit, making sure it was sealed. The instruments told him he was a bare ten miles above Ganymede now. One more swing around the poles would do it.
He peered out as the Dome came below and once again snapped on the radio.
'I'm going to come down and burn a path through those worms of yours. Watch me carefully, and jump to it when you see me land. I want that airlock open, or else.'
'But—'
'No buts!'
He was right overhead now. Just one ordinary-type gun would solve the whole problem, he thought. But Postal Ships didn't get guns. They weren't supposed to need them.
He centered the ship as well as he could on the Dome below and threw it into automatic pilot. Jumping from the control panel, he ran back toward the gun turret and slammed shut the plexilite screen. Its outer wall opened and the fuel-tank went tumbling outward and down. He returned to his control-panel seat and looked at the viewscreen. He smiled.
The fuel-tank was lying near the Dome—right in the middle of the nest of iceworms. The fuel was leaking from the puncture.
The iceworms writhed in from all sides.
'Now!' Preston said grimly.
The ship roared down, jets blasting. The fire licked out, heated the ground, melted snow—ignited the fuel- tank! A gigantic flame blazed up, reflected harshly off the snows of Ganymede.
And the mindless iceworms came, marching toward the fire, being consumed, as still others devoured the bodies of the dead and dying.
Preston looked away and concentrated on the business of finding a place to land the ship.
The holocaust still raged as he leaped down from the catwalk of the ship, clutching one of the heavy mail sacks, and struggled through the melting snows to the airlock.
He grinned. The airlock was open.
