The Year's Best Science Fiction, Vol. 20

Pull out again, in a long, astronomical-scale zoom. The pressure-suited figure is just one of many, human and machine. The machines outnumber the humans in number and variety. The valley floor is a hive of machine species. There are high-stepping nanofacturing robots, pausing to stab proboscises into the surface and release swarms of nanoassemblers. There are surveying machines, exchanging heliographs of laser light. There are great orange worm machines, burrowing deep in the regolith, chewing dead red rock into pumice. There are planters and fermentories-great, slow, sessile things-gulping in carbon dioxide atmosphere by the ton and reacting it with water and wan sunlight into organic matter. Living stuff. The stuff of worlds. There are the fleets of heavy-lift LTAs-the man in the suit is marshaling them on some precision maneuver-and smaller, nimbler sky-craft, zipping between the big slow dirigibles on their priority missions. There are track layers and road builders and brick makers and patient little spider machines that mortar them into the neat adobes for the humans. There are machines that build machines and machines that service machines and machines that program machines and machines that repair machines and everywhere is the green circle logo and sigil of ROTECH. Remote Orbital Terraform and Environmental Control Headquarters. Swarming machine life calls green out of the red; tentative, fragile plantations of gene-tweak grasses and mosses. Beneath human perceptions, the cleverest, the most important machines, the nanoassemblers, fuse red sand into silicon pillar. On the scale of planets, other hives of machines extend primeval run-water channels into canals to carry water from the thawing north pole to the terraformed lands of Grand Valley. A flash of light: eighty kilometers up in low, fast orbit, a vana, a spinning mirror of silver polymer, frail as a hope, rolls its focus on to its true target; the northern polar cap. The scale of the work in this four-thousand kilometer rift valley only becomes apparent at this kind of altitude. To the northwest the forest of towers rise above our ascending point of view. Their tops open out into branches, those branches into twigs, bare, waiting. To the east the towers are still growing, one kilometer, two kilometers. Farther east still, trillions of assemblers swarming in the subsoil are pushing the great root-buttresses out of chaotic mesa-lands of Eos and Capri. The wave of construction passes down the chasm like a slow, silicon spring. Another glitter of light, not from an orbital mirror this time, but sun catching the edge of the world roof, five kilometers above the wind-shaved hills of Coprates. Above it now, climbing fast. The world roof flows from the east like a river of glass that falls into red emptiness.

How to terraform Mars. Easy. Stick a roof over Valles Marineris. Real greenhouse effect. By the time it is complete, it will be visible from Earth, a bright white mote in the eye of the ancient red war god.

Higher now, past the littler, lower moon. Keeping precise pace with it on the other side of the planet is the SkyWheel, the spinning ground-to-orbit space-cable. All the humans, all the machines that build the bases and plants and the machines, were spun down this cable. But the real work of terraforming, the RO in the ROTECH, is done from orbit. Up beyond the vanas and the supercores, weaving a magnetic cocoon around this tectonically dead, defenseless world, are the orbital habitats and factories and mass drivers of the planetary engineers and terraformers. By the time humans can walk unclad under the Grand Valley roof, they will form a ring around the planet, a band of satellites. The night will glitter with them.

All in a construction worker’s visor; reflected.

Ashwin Mehta edges the heavy-lift flotilla in over the construction site. His belly sensors and satellite uplinks to ROTECH’s moon ring redoubt could guide him in with laser precision but human atavism endures. The gloved hands wave him down, and he follows. Spinners skitter clear. The winds that howl the full length of the rift valley have buried the load with sand: Ashwin’s trim-fans sweep it clear as he maneuvers with millimeter precision. He feels the lift cables go out of him: it is a physical, pleasurable sensation but not one for which his flesh body has an analogue.