“You accelerate halfway to your destination, turn around and decelerate for the second half of the trip.”

The physicist shook his head. “Short trips yes, longer trips no. You only need to accelerate for a few days to be going quite fast. Longer trips you should coast through the middle, to save fuel.”

The head adviser nodded, handed the others full cups. They sipped.

The mathematician said, “Travel times will change so radically. Three weeks from Mars to Uranus. Ten days from Mars to Jupiter. From Mars to Earth, three days. Three days!” She looked around at the others, frowning. “It will make the solar system something like Europe in the nineteenth century. Train trips. Ocean liners.”

The others nodded. The engineer said, “Now we’re neighbors with people on Mercury, or Uranus, or Pluto.”

The head adviser shrugged. “Or for that matter Alpha Centauri. Let’s not worry about that. Contact is a good thing. Only connect, the poet says. Only connect. Now we will connect with a vengeance.” He raised his cup. “Cheers.”

Nirgal got in a rhythmand kept it all day. Lung-gom-pa. The religion of running, running as meditation or prayer. Zazen, ka zen. Part of the areophany, as Martian gravity was integral to it; what the human body could achieve in two fifths the pull it had evolved for was a euphoria of effort. One ran as a pilgrim, half worshiper half god.

A religion with quite a few adherents these days, loners out running around. Sometimes there were organized runs, races: Thread the Labyrinth, Chaos Crawl, the Transmari-neris, the Round-the-Worlder. And in between those, the daily discipline. Purposeless activity; art for art’s sake. For Nirgal it was worship, or meditation, or oblivion. His mind wandered, or focused on his body, or on the trail; or went blank. At this moment he was running to music, Bach then Bruckner then Bonnie Tyndall, an Elysian neoclassicist whose music poured along like the day itself, tall chords shifting in steady internal modulation, somewhat like Bach or Bruckner in fact but slower and steadier, more inexorable and grand. Fine music to run by, even though for hours at a time he didn’t consciously hear it. He only ran.

It was coming time for the Round-the-Worlder, which began every other perihelion. Starting from Sheffield the contestants could run east or west around the world, without wristpad or any other navigational aid, shorn of everything but the information of their senses, and small bags of food and drink and gear. They were allowed to choose any route that stayed within twenty degrees of the equator (they were tracked by satellite, and disqualified if they left the equatorial zone), and all bridges were allowed, including the Ganges Strait Bridge, which made routes both north and south of Marineris competitive, and created almost as many viable routes as contestants. Nirgal had won the race in five of the nine previous runnings, because of his route-finding ability rather than his speed; the “Nirgalweg” was considered by many fell runners to be in the nature of a mystical achievement, full of counterintuitive extravagance, and in the last couple races he had had trackers following him with the plan of passing him at the end. But each year he took a different route, and often he made choices that looked so bad that some of his trackers gave up and took off in more promising directions. Others couldn’t keep up the pace over the two hundred days of the circumnavigation, crossing some 21,000 kilometers — it required truly long-distance endurance, one had to be able to sustain it as a way of life. Running every day.

Nirgal liked it. He wanted to win the next Round-the-Worlder, to have won a majority of the first ten. He was out researching the route, checking new trails. Many new paths were being built every year, there had been a craze recently to inlay staircase trails in the sides of the canyon cliffs and dorsa and escarpments that everywhere seamed the outback. The trail he was on now had been constructed since he had last been in this area; it dropped down the steep cliff wall of a sink in the Aromatum Chaos, and there was a matching trail on the opposite wall of the sink. Going straight through Aromatum would add a fair bit of verti-cality to a run, but all flatter routes had to swing far to north or south, and Nirgal thought that if all the trails were as good as this one, the cost in elevation might turn out to be worth it.

The new trail occupied angled cracks in the blocky cliff wall, the steps fitted like the pieces of a jigsaw puzzle, and very regular, so that it was like running down a staircase in the ruined wall of some giant’s castle. Cliffside trailmaking was an art, a lovely form of work that Nirgal had joined from time to time, helping to move cut rocks with a crane, to wedge them into position on top of the step below — hours in a belay harness, pulling on the thin green lines with gloved hands, guiding big polygons of basalt into place. The first trail builder Nirgal had met had been a woman constructing a trail along the finback of the Geryon Montes, the long ridge on the floor of lus Chasma. He had helped her all of one summer, down most of the ridge. She was still in Marineris somewhere, constructing trails with her hand tools and high-powered rock saws, and pulley systems with superstrong line, and glue bolts stronger than the rock itself — painstakingly assembling a sidewalk or staircase from the surrounding rock, some trails like miraculously helpful natural features, others like Roman roads, others still with a pharaonic or Incan massiveness, huge blocks fitted with hairline precision across boulder slopes or large-grained chaos.

Down three hundred steps, counting, then across the sink floor in the hour before sunset, the strip of sky a velvet violet glowing over dark cliff walls. No trail here on the shadowed sand of the sink floor, and he focused on the rocks and plants scattered over it, running between things, his glance caught by light-colored flowers on top of round-barreled cacti, glowing like the sky. His body was also glowing, with the end of the day’s run, and the prospect of dinner, his hunger a gnawing from within, a faintness, getting more unpleasant by the minute.

He found the staircase trail on the western cliff wall, up and up, changing gears into the uphill push stride, smooth and regular, turning left and right with the switchbacks, admiring the elegant placement of the trail in the crack system of the cliff, a placement that usually had him running with a waist-high wall of rock on the air side, except during the ascent of one bare sheer patch of rock, where the builders had been forced to the extremity of bolting in a solid magnesium ladder. He hurried up it, feeling his quadriceps like giant rubber bands; he was tired.

On a plinth to the left of the staircase there was a flat patch with a great view of the long narrow canyon below. He turned off the trail and stopped running. He sat down on a rock like a chair. It was windy; he popped his little mushroom tent, and it stood before him transparent in the dusk. Bedding, lamp, lectern, all pulled hastily from his fanny pack in the search for food, all burnished by years of use, and as light as feathers — his gear kit altogether weighed less than three kilos. And there they were in their place at the back, battery-powered stove and food bag and water bottle.

The twilight passed in Himalayan majesty as he cooked a pot of powdered soup, sitting cross-legged on his sleeping pad, leaning back against the tent’s clear wall. Tired muscles feeling the luxury of sitting down. Another beautiful day.

He slept poorly that night, and got up in the predawn cold wind, and packed up quickly, shivering, and ran west again. Out of the last Aromatum jumbles he came to the northern shore of Ganges Bay. The dark blue plate of the bay lay to his left as he ran. Here the long beaches were backed by wide sand dunes, covered by short grass that made for easy running. Nirgal flowed on, in his rhythm, glancing at the sea or into the taiga forest off to the right. Millions of trees had been planted along this coastline in order to stabilize the ground and cut down on dust storms. The great forest of Ophir was one of the least populated regions on Mars; it had been rarely visited in the earlier years of its existence, and had never been host to a tent town; deep deposits of dust and fines had discouraged travel. Now these deposits were somewhat fixed by the forest, but bordering the streams were swamps and quicksand lakes, and unstable loess bluffs that caused breaks in the lattice roof of branches and leaves. Nirgal kept to the border of forest and sea, on the dunes or among stands of smaller trees. He crossed several small bridges spanning river mouths. He spent a night on the beach, lulled to sleep by the sound of breaking waves.