EXCERPT

     Red sky at night, sailor's delight; red sky at morning, sailors take warning. But what if the sky is red all the time? Ed Shepard looked up at the salmon pink glow of late morning on Mars and shivered despite the heat in his pressure suit. When he worked miles away from the nearest colony, he'd sometimes feel a moment of loneliness and isolation. He'd been on Mars for three years, one of the first construction workers to qualify for sponsorship to make the trip. Having worked on construction sites from the deserts of the Middle East to the ice fields of Antarctica, he'd never thought the vast emptiness of a new world would bother him, but it did now. The unending sea of bloody red rocks and sand, cut with streaks of black and orange, filled his view all the way out to a horizon that was too close. He knew he'd feel better if he could smell his dusty surroundings -- he related best to new environments by smell -- but all he could detect was an odor reminiscent of old gym shoes in the recycled air of his suit.

     Ed heard a loud ping when his tracker made contact with one of the diggers. Two of the robot excavators, controlled part-time by human teleoperators at the Vulcan's Forge colony, had collided with each other the previous day. They were precision diggers, designed to work in tight spaces, but the cheap models covered with tools would often get caught between rocks or on other robots. During the night, the interlocked robots wandered away from their work site to fall in a hole somewhere, hidden from the satellites, and it was Ed's job to find them. His partner, Larry DiMarco, searched on the opposite side of the ridge that separated the Umbra Labyrinthus -- the Labyrinth of Shadows -- from the Noctis Labyrinthus -- the Labyrinth of Night. Both areas were mazes of narrow canyons at the summit of the Tharsis uplift, a volcanic region dominated by Mons Olympus and three other shield volcanoes. The robots couldn't have chosen a worse place to fall in a hole.

     Following the position indicators on his handheld tracker, Ed shuffled over to the opening of a large volcanic vent -- maybe eighty feet across -- that angled steeply down into the darkness. A few years earlier, surveys of this area with deep-ground-penetrating radar discovered hot water reservoirs trapped just three thousand feet beneath the surface. Deep geothermal heat sources melted subsurface ice to form trapped pools of water. Water mining rigs were set up in volcanic vents such as this one because the lava tubes often ran deep under the surface, simplifying access to the water pockets. However, he couldn't see any survey markers, so there was little chance of finding a well-worn trail to a water mining rig. Ed switched on his flashlight, wishing that his sponsor had provided one of the fancier pressure suits with the big lights built into the chestplate and helmet. He peered into the pit as he signaled his partner, noting that he could work his way down the slope without a rope. If the vent got steeper as he ventured lower, he'd wait for Larry to arrive before going any further. Technically, he knew he should wait for Larry before entering the vent, but it would take his partner at least ten minutes to walk over the ridge and Ed needed his breakfast. The sooner he could find the robots, the sooner they could get back to the rover and eat.

     Larry's voice barked in his ears. After twenty years of working at noisy construction sites, he'd developed the habit of shouting, even when wearing a pressure suit -- only one of many irritating habits. "Shep? Ya got 'em?"

     "Tracker says they're in a hole," said Ed, turning his audio volume down. "I'm goin' in to eyeball it."

     "Better wait for me."

     "Yeah, I'll wait for ya. I'll be the guy standin' here with the two robots."

     "You gonna haul 'em out all by yourself, tough guy?"

     "If you weren't such an old lady, you'd be down here already."

     "You're gonna look awful silly when ya fall down that hole and I have to winch ya out."

     "I'll take my chances. I'm hungry."

     "Suit yourself, ace."

     Ed rolled his eyes and started down the vent, picking his way among the deep gouges in the rough reddish-brown rock. When he was about sixty feet down, he noticed that the walls of the vent didn't look quite the same as other volcanic tubes he'd seen on Mars. The walls seemed rougher, scored by explosive pressure but not melted from the heat of the lava. Something unusual about the local rock, maybe, but he wasn't a geologist and he didn't really care that much. The tracker pinged again, its strong signal implying that the two diggers were still close together wherever they'd fallen.

     The vent steepened and narrowed as Ed continued his lurching progress. Almost an hour of strenuous effort brought him to a ledge where the walls of the vent sparkled with shards of milk-white volcanic glass, as if someone had broken dishes at a fancy picnic. He picked up one of the flat shards and frowned at the sharp edges, wondering how hot glass could have broken that way. Maybe a sudden change in temperature as the glass cooled? The thick shard slipped from his glove despite his tight grip.

     Ed aimed his flashlight down beyond the ledge. The drop was vertical now, maybe sixty feet to the next flat area. Rubble had narrowed the opening in the vent to about ten feet across, but a wider chamber yawned beneath the hole. He could climb down further with the spider line, but he'd need Larry's help to haul the robots out. Naturally, the perverse little machines had rolled far into the vent, making it impossible for Ed to drag them out by himself. Then he noticed that the floor of the pit was glowing. He shut off the flashlight to be sure, and found that he no longer needed it. The walls of the chamber below him were coated with the white glass, glowing enough to provide sufficient light for his needs. He crouched for a better look, then bent over and poked his head through the opening.

     The diggers sat on the floor of a horizontal tube with smooth white walls. Their running lights were off, but one of the robots twitched. Each spasm jerked the six tool arms, making the digger look like a sand crab that had been flipped on its back. The dead unit had a trenching tool buried in its side, presumably left there after the two robots broke apart from the impact after their tumbling dance of death. Lubricant leaked from the wounded digger, forming a pool of brown liquid beneath the two machines.

     "Larry? I see 'em."

     "Good. I'm tired," he said, breathing hard.

     "We'll need both spider lines to get 'em outta this hole."

     "Yeah, I figured."

     Ed continued studying the tube. It looked straight, like a subway tunnel, ending at rockfalls that blocked both ends. "And there's somethin' else, Larry."

     "Let me guess. Ya want me to carry your sorry ass outta there."

     Ed's gaze fell on a glint of metal protruding from the rockfall at the east end of the tunnel, less than a hundred feet away. "There's a tunnel down here, and it ain't natural."

     "Water miners?"

     Ed patched the end of his spider line to the ledge and lowered himself into the hole. "I don't think so. There ain't no rig, unless it got buried in a cave-in. But this whole tunnel looks artificial, like the walls are coated with white glass stuff."

     "Nobody's worked this area. No exploration markers up top."

     Ed slipped on the smooth floor as his boots made contact. When he regained his footing, he stepped on areas that were covered in sand so that he could get better traction. Free of the spider line, he walked over to the shiny metal protruding from the rockfall. It didn't look like a natural deposit, more like chrome that had been formed into a delicate curving shape. Elaborate patterns were visible at close range.

     He reached out to touch it.

     His head exploded with light.

     "Ed?" Larry's voice, the last human sound he'd ever hear.

     Ed tried to scream, but he couldn't make a sound. He slumped against the metal surface, his brain burning with internal fire. The coppery taste of blood filled his mouth. His body twitched while nerve impulses misfired in a high voltage flow of energy. As his eyes rolled back into his head, a mental image of a shadowy face tried to take shape before his synapses failed.

     When the incomplete face faded away, to be replaced by the brilliant multi-colored glow of expanding gases from an exploding star, he felt a sense of loss, certain that he'd failed some sort of test he didn't understand.

     And failure meant death.