Below Mercury

by Mark Anson

  ‘Okay.’

  There was a pause while Wilson found the sealant gun in his tool pouch. The sound of his breathing came over the speakers on the command deck. He moved slowly, taking his time.

  Wilson held the gun up to where the pipe entered the coupling, and pressed the nozzle of the gun into the join. He checked that he was still securely anchored to the ship, and squeezed the trigger gently. A thin bead of transparent gel oozed from the nozzle and spread along the join. He withdrew the gun, and then sprayed the gel with a short burst of setting compound from a pressurised canister.

  The gel set solid in moments, and Wilson stayed there, watching the join carefully. After a couple of minutes, he was satisfied that he’d sealed the leak, and he stuck a red arrow close by, pointing at the join, so that they could find it again.

  Wilson stowed his tools back in the tool pouch and unfastened the rigid braces holding him in place. He clipped his safety line onto a ladder that led back to the tug’s EVA airlock.

  He moved back to the airlock, moving only one hand or foot at a time as he passed along the ladder, keeping his feet placed on the rungs to stop his body from drifting away. Working in zero gravity needed slow, careful movements, always against a firm purchase, and Wilson resisted the temptation to rush things.

  He manoeuvred himself carefully round the main antenna mount, and swung his legs and lower body through the open outer hatch of the airlock. He paused there for a moment, his head and shoulders looking out of the hatch, and took in the scene around him.

  Directly in front of him, behind the black disc of the sunshade, the Sun blazed, its titanic light held at bay, and the stars shone out clear and unwavering in the blackness of space. To his left, in the constellation of Gemini, Wilson could see the brilliant crescent of Venus, and over his left shoulder, between Cancer and Leo, the small, pink dot of Mars.

  He looked sunward again, wondering if he could glimpse their destination, but checked himself. Mercury was invisible, hidden behind the Sun. The small planet was flying past its furnace-like perihelion, racing round the Sun on its penultimate orbit before their meeting in three month’s time.

  Instead, he turned to the right, scanning the stars, until he found the brilliant, creamy-coloured point of light that was Jupiter.

  He took a long look at the distant planet. Jupiter’s giant moons, worlds in their own right, were invisible to the naked eye, but he could imagine that they were there, circling their massive primary. Volcanic Io, closest to the planet, its interior kept molten by competing tidal forces.. Then the blue-white moon of Europa, its hidden oceans covered with a thick crust of ice. Giant Ganymede – a world even bigger than Mercury – and then the cold, pock-marked ball of Callisto circling beyond the radiation belts.

  He wondered what the view was like from Valhalla Base, on Callisto. Were they watching the faint light of the distant Sun reflecting off the fields of blackened ice, or was it dark in their alien sky, with the disc of Jupiter waxing above the mountains?

  As he watched, he found his mind wandering in a familiar direction, and he made up his mind then, floating halfway into the airlock; he wanted to go out there, out to Jupiter.

  Once this mission was over, he would have enough flying hours in space to apply for a posting to Callisto. It would cost him three years of his life, with two of them spent in stasis on the long voyages there and back, but he would come back a rich man, with an almost guaranteed promotion to captain.

  It was a tempting, exhilarating thought, and all he needed to do was complete this routine mission. His flying hours were racking up with every day that passed, and this EVA would look good in his logbook, too. Not many people got a chance like this so early in their career, and he intended to make the most of it.

  The thought dragged him back to the present, and he realised he had been standing there for longer than he had intended. Better get inside now.

  Before he closed the airlock hatch, he took one last, slow look at the stars.

  Soon, they would be too close to the Sun and its deadly radiation to risk venturing outside the protection of the ship. This was probably his last chance to see the stars and planets like this, with just the thin plastic of his helmet visor between him and the Solar System, until they reached Mercury.

  The emptiness of space stretched into infinity all around him, silent, vast and still. The Baltimore fell through the vault of stars towards the Sun and the empty planet that awaited them, without any hint of its incredible speed.

  The only sound was his breathing, and the steady pulsing of blood in his ears.

  ‘See you again soon,’ he said in a quiet voice, and he retreated into the airlock, closing the hatch behind him.

  PART III

  Chao Meng-fu

  CHAPTER NINETEEN

  Innermost and smallest of the Sun’s family of planets, Mercury floats in the silent emptiness of space.

  Mercury is so close to the Sun that it falls round in just 88 days, swinging out slow and wide on one side of its eccentric year, then racing close and fast at the other, a mere third of the distance from the Earth to the Sun.

  Time and tide has slowed Mercury’s rotation, and locked it into a permanent rhythm, turning exactly twice on its axis for every three circuits round the Sun, so that Mercury’s burning day is far longer than its year. With no atmosphere, and only a feeble magnetic field to protect itself, Mercury is alone and exposed to the full might of the Sun’s heat and radiation.

  Now, on August 9, 2151, just six days short of Mercury’s fearsome perihelion, a bloated Sun three times the diameter of the one seen from Earth crawls towards its searing noon. The day has lasted over 900 hours from sunrise, baking the surface of Mercury to temperatures that would turn many metals to pools of shimmering liquid. There is no air in Mercury’s jet-black sky to carry the heat away to cooler climes; the atmosphere escaped into space long ago, forced away by the intense heat and silent solar wind.

  The motion of the Sun, as it nears noon, is alien and strange; it has already slowed to a near-halt in the sky. Soon, it will reverse direction for a few days, before continuing on its slow journey across the sky.

  Stranger still, on this tiny world of furnace-like heat, is what lies hidden at its poles.

  Mercury spins round the Sun in an almost precisely vertical orientation with respect to its orbit; the Sun’s mighty grip on the tiny world does not permit any tilt to bring the seasons.

  At the poles, the Sun circles the distant horizon, never setting, and the slanting sunlight that glints across the rims of deep craters cannot penetrate into their depths. At the bottoms of these craters there are deep, cold places that have never seen the Sun, and in their depths, water from the impacts of ancient comets has frozen into great fields of glittering ice.

  The ice is black from the layers of dust and impact ejecta in its depths, and the frozen ammonia, methane, and other chemicals that the comets brought from the furthest reaches of the Solar System, remnants of the primordial solar nebula. In the coldest, deepest craters, some of the ice fields are billions of years old and hundreds of metres thick. Within them are trapped millions of tonnes of the rare isotope helium-3, brought here by the comets, or implanted in the ice by the solar wind.

  Helium-3 is the wonder-fuel of the twenty-second century. It can be forced to join with deuterium in the cores of fusion reactors to produce titanic amounts of energy. It produces little dangerous radiation, and it leaves no long-lived wastes or greenhouse gases. Helium-3 provides power almost beyond imagination. It has replaced all fossil fuels for power generation, reducing carbon emissions on Earth to levels not seen since the nineteenth century. It provides the power to drive the gigantic atmosphere processors on Mars, slowly changing the air over hundreds of years to terraform the planet.

  There is no natural helium-3 left on Earth; it disappeared long ago under the recycling tectonic plates of the crust. It cannot be created on Earth by any safe or economic process. The only economic sources are in
the ice deposits of Mercury, or on a few remote worlds in the Outer Solar System.

  At billions of times the price of oil, it remains the most precious substance ever found.

  Many years ago, Mercury was home to a dozen mines, extracting helium-3 from the black ice that lay in the polar craters, glistening under the stars.

  Now though, the skies over Mercury are empty; the fleets of circling tugs and tankers are long gone.

  Once the automated refineries in the Outer Solar System began to deliver helium-3 to Earth, the price of the precious isotope fell. The labour-intensive mines on Mercury became uneconomic, and closed one by one, until only Erebus Mine remained, surviving on deposits of rare metals deep below the crater plain.

  In 2142, the mine was abandoned following the accident. Mercury was left alone once more, circling with the silent dead in the emptiness of space.

  It is cold in the craters at Mercury’s poles, a cold that has existed since the beginning of time. Out on the ice fields, the mining machines lie abandoned, their cutter arms frozen in strange poses, black silhouettes against the sea of stars above.

  A brighter speck of light moves slowly against the backdrop of the distant stars; after a voyage of 97 days through the deeps of interplanetary space, the Baltimore is approaching the silent planet.

  Once, people working out on the ice fields would have lifted their heads and looked up at the brightening star that rose towards the zenith. Now, only the mining machines are left, frozen in the ice, and they do not stir.

  CHAPTER TWENTY

  ‘Don’t look at the Sun.’

  Clare Foster’s voice cracked out across the Baltimore’s command deck as a wave of brilliant light swept across the cockpit windows. The glass darkened automatically, but the six members of the mission team could still feel the Sun’s heat and glare as the light moved over them.

  They were all back on the command deck, strapped into their seats, for the most dangerous part of their voyage to Mercury. The seats had been reoriented for the thrust manoeuvres, so that they faced away from the engine, and Clare and Steve’s positions now looked forward, through the main docking windows at the front of the crew compartment.

  For the past few days, Mercury had been growing in the long-range camera displays, from a brilliant crescent rising out of the Sun’s glare, waxing to a perfect half-full as the ship chased the planet along its orbit. Now the planet lay directly ahead of them, filling the sky, bisected at the line between night and day.

  The tug was turning round, aligning itself so that the engine pointed forward, ready to fire against their direction of motion and brake them into orbit round Mercury. Far away on the body of the tug, the thrusters burned again briefly, and the tug slowed and stopped in its new attitude, accurate to a second of arc.

  The six large solar panels and the giant sunshade, that had shielded them from the relentless glare of the Sun over the past three months, started to fold up now. The panels and sunshade were too fragile to withstand the forces of the orbit insertion burn, and the tug could manage without the sunshade for a short time, before the Sun’s heat made it essential to spread the protective shadow around the vessel again.

  Monitors on the command deck showed the crew the forward view from one of the inspection cameras. The four passengers watched the scene in fascination. Lit at an extreme angle by the Sun, the stark shadows of craters and scarps gave the planet’s edge a strange, half-eaten appearance. From this distance, it was impossible to believe that they were going to miss the planet; it filled the field of view, and the tug seemed to be plummeting headlong towards its centre. The navigation displays, however, told the true story; their flight path would take them over the North Pole, missing Mercury by a scant 200 kilometres.

  The minutes to ignition counted down.

  In the tense quiet of the command deck, Clare spoke.

  ‘Okay, electrical power to batteries. Shut down power generators.’

  Wilson punched switches on the engine controller panel, watching as the power levels fell. On another console, he brought up the fuel system, readying the giant tanks of ammonia and the turbopumps to deliver hundreds of tonnes of fuel to the engine.

  ‘Arm engine for firing.’ Clare spoke quietly, watching the approach display and the minutes and seconds to the orbit insertion.

  ‘Control drums armed. Fuel system is pressurised and armed. Safeties off.’ He looked across at Clare. ‘Ready to bring up power.’

  ‘Reactor to fast idle.’

  Wilson flipped a safety cover off a switch and pressed it, holding it down while the reactor power increased, ready for the insertion burn.

  ‘Reactor power rising.’ Wilson released the starting switch as the temperature readings rose inside the reactor’s deadly heart. He watched as the core stabilised at the lowest power setting, verifying items from the checklist on the screen in front of him. Finally, he was satisfied, and flipped off the safeties for full power.

  ‘Reactor stable at fast idle. Coolant flow normal. Neutron flux is normal.’ He glanced round the instruments one last time. ‘Ready for ignition.’

  Clare gave her full attention to the approach display, which showed the relative orbital paths of the ship and Mercury, and the long deceleration vector that they had to achieve for successful orbital insertion. In all the Solar System, few manoeuvres were more dangerous if anything went wrong, and they were on their own, far from any help.

  She took a deep breath. It was now or never.

  ‘Okay, let’s do it. Set engine to autopilot.’

  ‘Engine to autopilot. Ignition sequence armed.’ Wilson’s eyes flickered round the engine and fuel situation displays, watching for any signs of trouble.

  Clare checked the plan loaded in the autopilot for the twentieth time, looking for any error. Her hands moved in an unconscious cycle, hovering over the reactor scram button, then the autopilot mode panel, then the abort button, in a practised sequence.

  She wished she wasn’t so nervous; she was convinced the others were picking it up and were watching her for signs of not being able to cope.

  Nearby, Matt gripped the arms of his seat. He wished he were more than a passenger, and that he had something to do to take his mind off the anxiety. He watched Clare as she sat in the commander’s seat, monitoring the countdown, obviously in control. He hated orbital insertion burns; they were the tensest part of any flight, and he couldn’t relax until the burn was over.

  ‘Deep Space Control, Mercury Two Zero Seven commencing Mercury orbit insertion, firing in sixty seconds.’ Wilson’s voice would not reach Earth for another nine minutes, and by then, the crew’s fate would be determined, one way or another.

  ‘Firing in forty seconds.’

  Ahead of the ship, Mercury had grown so large that fine detail in the surface features could be made out on the displays. Wandering lines of rilles and lobate scarps, smooth plains, and crater upon crater filled the field of view, ready to smash them to fragments if they miscalculated their approach.

  The planet’s surface continued to expand, until it filled their field of view in every direction. The sensation of falling straight towards the surface was overpowering, and Matt nervously checked the navigation displays, to reassure himself that they weren’t going to smash into the planet.

  At last, however, just as he thought that the displays were wrong and that impact was unavoidable, he realised that the landscape was slowing in its headlong rush towards them, and had begun to move past in front of the ship. As he watched, the sense of lateral motion increased, the surface moving faster and faster until it seemed to flow past them like a river, a mere hundred kilometres below.

  The Sun slid towards the horizon on their left, and the shadowed terrain below them, great bowls of craters made billions of years ago, darkened into night.

  ‘Fifteen seconds to firing. Ignition sequence started.’ Wilson reached up and tightened his seat straps.

  The bloated disc of the Sun shrank to a point, and dis
appeared below the horizon, plunging the space tug into the darkness of Mercury’s shadow.

  ‘Ignition sequence commit. Firing in five, four, three—’

  Far behind them, at the end of the long propellant tanks of chilled liquid ammonia, the waiting vanes of the turbopumps spun up to their full rated power, a dizzying 26,000 revolutions per minute, forcing the cold ammonia fuel at tremendous pressure into the waiting engine. Huge volumes of ammonia surged into the reactor, right into the heart of the blizzard of neutrons, as the reactor came to full power.

  The incandescent core of the reactor blazed a searing ultra-violet, a captive sun pouring gigawatts of pure energy into its surroundings. The ammonia fuel flashed into superheated gas, and erupted through the engine nozzles in an enormous, spreading flame.

  ‘—zero.’

  A giant hand gripped the space tug and shoved it backwards in space, pressing the crew into their seats. The command deck quivered, and a steady rumble came through the ship’s structure from the distant nuclear furnace.

  ‘Full thrust. Reactor stable.’ Wilson’s eyes never left the engine status displays, flicking over the readouts as he watched the fuel inlet pressures and flow, the reactor power output, and the exhaust gas temperature.

  After so long in low-gravity and weightless conditions, the deceleration was hard on their bodies; Matt found it an effort to breathe as his chest was squeezed in by the tremendous thrust.

  By turning his head, he could see the planetary approach display on Clare’s navigation display. The white line of the tug’s track was changing, curving closer to the globe of Mercury with each passing minute, the ship’s headlong rush braked by the mighty thrust of the nuclear engine. The magenta line of the target orbit seemed to curve impossibly close to the planet – surely there was no way the ship could slow down enough?