Oddly, she felt as if the shades of Armstrong and Muldoon were beside her, as if she was echoing their first, famous expedition. It was a thought that somehow diminished this moment.

She turned to face Challenger. The MEM was an angular pyramid, huge before her, silhouetted against the light of the shrunken sun, and propped up in an unlikely fashion on its six fold-down legs. She was still in the shadow of Challenger. The ambient light was like a late sunset, with Challenger drenched in a weak, deep pink color; against that, the rectangle of fluorescent light from the hatch, framing Stone, was a harsh pearl-gray, startlingly alien.

The dominant red tones came from dust suspended in the air. There was about ten times as much dust, she knew, as over Los Angeles on a smoggy day. And no rain, ever, to wash it out.

She walked away from Challenger then, working her way over into the sunlight, moving along the shadow of Challenger, toward the west. The MEM’s shadow was a long, sharp-edged cone on the rocky surface before her.

She passed beyond the edge of the shadow and into the light.

She turned. Sunlight shone into her face, casting reflections from the surfaces of her faceplate.

Sunrise on Mars: the sky here was different, the way the light was scattered by the dust…

The sun, rising above the silhouetted shoulders of Challenger, was surrounded by an elliptical patch of yellow light, suspended in a brown sky. It looked unreal.

The sun was small, feeble, only two-thirds of its size as seen from Earth.

She shivered, involuntarily, although she knew that her suit temperature couldn’t have varied; the shrunken sun, the lightless sky, made Mars seem a cold, remote place.

She turned around, letting her camera pan across the landscape. The Martian dust felt a little slippery under her boots.

She stepped farther away from Challenger, her line of footprints extending on into the virgin regolith. She felt as if the long, thin line of communications attaching her to Challenger and her home planet was growing more attenuated, perhaps fraying, leaving her stranded on this high, cool plain.

The land wasn’t completely flat, she saw now, as the light continued to increase; there was a subtle mottling in the shading. And she made out what looked like low sand dunes, off to the west. But the dunes were more irregular than terrestrial sand dunes, because, she guessed, of the small size of the surface particles; the dunes were actually more like drifts in the dust.

Away to the west, she saw a line, a soft shadow in the sand. It looked like a shallow ridge, facing away from her.

She walked forward, farther from the MEM.

After perhaps fifty yards she came to the ridge. It turned out to be the lip of a small crater, quite sharply defined, a few dozen yards across, embedded in the floor. But the crater walls were worn, and there was a teardrop-shaped mound behind it.

That mound had to be an erosional remnant, streamlined like the remnants found in terrestrial braided streams. And she thought she could see stratification in the sides of the remnant. It was just like the scablands, after all.

She began to step down into the crater, clumsily; her legs were stiff, and dust swirled up around her, sticking to her legs and her HUT.

Her faceplate was misted up, her breath rapid. She leaned forward.

In the lee of the crater rim, something sparkled, something that finally banished the lunar ghosts of Armstrong and Muldoon from this moment, something that made her feel that her life’s circle had closed, at last. I guess I got to step into the picture after all.

It was frost.

She leaned sideways, and stretched down to the crater’s floor, awkwardly. She scraped at the dust with her fingers. Her fingers cut easily into the surface, leaving sharp trench marks. I’m like a kid, digging on a beach. A planetwide beach. Everywhere she dug, she found the same soft, powdery surface, the same cohesiveness, what looked like pebbles.

She lifted her glove to her face, to get a closer look at the dirt. It was oddly frustrating. The bit of regolith was very light, so light she couldn’t even feel its weight. She couldn’t even feel its texture because of the thickness of her clumsy suit. And the glare of the rising sun in her glass faceplate made it difficult to see, and the whir of pumps, the hiss of the radio, cut her off from whatever thin sounds were carried by the Martian winds.

She had a sense of unreality, of isolation. She was here, but she was still cut off from Mars. It wasn’t like a field trip at all.

She closed her fingers over the sample; the little “pebbles” burst and shattered. They were just fragments of a calichelike duricrust.

She tipped her hand and let the crushed dust drift back to the surface; much of it clung to the palm of her glove, turning it a rust brown.

She took the diamond marker out from the sample pocket on her suit. She held the little coin in her hand; it caught the sunlight and refracted it, turning its glow to a bright scarlet, jewellike, against the ocher of Mars.

She felt a sudden, and unexpected, surge of pride. She distrusted patriotism intensely; and maybe this expedition, these few days of scrambling over Mars like rabbits, really was all a grand technocratic folly. But the fact was that her country had — in little more than two centuries of existence — sent its citizens to walk on the surfaces of two new worlds.

And if some calamity were to wipe Earth clean of life before anyone decided to come again, this little marker, with its flag, would still be here, as a monument to a magnificent human achievement: this, and the remnants of Challenger, and three Lunar Module descent stages on the surface of the Moon.

And to think we nearly didn’t come here; to think, after Apollo, we might have closed down the space program.

Carefully she dropped the marker and let it float through the weak gravity down into the hole she’d dug, where it lay, sparkling, in the base of the crater.

Then, silently, she reached into her pocket again. With some difficulty, she drew out a small silver pin. Its 1960s design was tacky: a shooting star soaring upward, a long, cometlike tail.

For you, Ben.

She dropped the pin into the little ditch, after the diamond marker. Then she kicked dust back into the hole, and scuffed over the surface.

The footprints Armstrong and Muldoon had left behind on the Moon’s surface were still there — would remain there for many millions of years, until micrometeorite erosion finally obliterated them. But it was different on Mars. The prints she was making today would last for many months, perhaps years; but eventually the wind would cover them over.

In a few years her footprints would be erased by the wind, the first little pit she’d dug all but untraceable.

“…Natalie?”

She hadn’t said anything, she realized.

She turned to Challenger. The human artifact was a squat, white-painted toy, diminished by the distance she had come; the sun made the sky glow behind it. She could still see the pearl-gray interior of the airlock, embedded at the center of the MEM, and above that she could make out the fat cylinder of the ascent stage, with its propellant tanks clustered like berries around a stalk.

There was a single set of footsteps, crisp in the duricrust, leading from Challenger to where she stood, beyond the circular splash of dust from the MEM’s landing rocket. They looked like the first steps on a beach after a receded tide; they were the only footsteps on the planet.

By God, she thought, we’re here. We came for all the wrong reasons, and by all the wrong methods, but we’re here, and that’s all that matters. And we’ve found soil, and sunlight, and air, and water.

She said: “I’m home.”