After a time, they fell silent, and he listened to the soft hiss of the static on the air-to-ground loop.

And eventually, after much debate and protest, official permission was granted to proceed with the mission.

First, Arkady had to change the plane of the orbit of his Soyuz.

At present, the orbit was a ground-hugging circle, angled at some twenty-five degrees to the Moon’s equator, a shallow tilt. Now, Arkady needed a ground track that would take him over the Moon’s South Pole. So his orbit must be tipped up at a more jaunty angle, eighty degrees or more, so that he looped over both poles.

Steering a spacecraft to a new orbit was not a question of turning a wheel, like a car. The Soyuz’s main propulsion system would have to burn at an angle to its present velocity vector, gradually pushing it sideways, like a tug hauling at a supertanker.

The velocity changes required were well within the capabilities of Soyuz with its Block-D booster — which was, after all, capable of returning him all the way from lunar orbit and to the Earth — and it was a neat exercise in three-dimensional orbital mechanics, which Arkady conducted in conjunction with the ground, to calculate the rocket burns required.

But the manoeuvre would absorb most of the fuel reserve put aside for the return of Soyuz to the Earth, whether Arkady proceeded with the landing or not.

And so it was that when Arkady felt the gentle push of the propulsion system at his back, he knew he was, already, committed.

Arkady allowed himself a complete orbit, in his new polar orientation, before he began his descent.

As he passed over the Earth-facing hemisphere of the Moon, he spoke to Geena.

…Are you lonely up there? Do you miss me?

“Yes,” said Arkady. Yes. But I cannot tell you how much. Not when the whole world, including your ex-husband, is listening in. “I even miss Baikonur.”

Baikonur? The steppe?

“The steppe has its beauty. At this time of year the grass and flowers have burned off, and the steppe has turned grey, save for the green of the camel thorn and the pale pink of the saxifrage flowers. Sometimes after the rain, puddles form, like little lakes, in the middle of the salty desert. Swans come to breed there!…”

It sounds beautiful.

“It can be.”

Now, unexpectedly, Geena sang a song for him. Her voice was hesitant, not very tuneful, her Russian accent poor. But he recognized it immediately. It was a favourite from his childhood, On the Porch Together. Her voice was nervous and thin, reduced to a scratch by the radio loop, and it all but reduced him to tears. She had learned this song from his family, and had now brought it to the Moon for him. And she was filling his heart. Most Americans could never understand the importance of such simple human moments.

And when she was done, Geena sang one of Yuri Gagarin’s favourites — so it was said, anyhow — called I Love You, Life. All the cosmonauts knew this one, and he joined in, but his voice was weak and he feared he would lose control.

At last, without warning, he sailed around the rocky limb of the Moon, and the radio signal turned to mush, cutting short her song.

He turned off the receiver, and drifted away into the empty, ticking cabin.

In solitude once more, Arkady watched the shadows lengthen, and, for the last time, he sailed into the shadow of the Moon.

It was necessary for his craft now to perform the final burn. As so often happened with the key events of this mission, it seemed, it must be done here, in the radio shadow of the Moon, when he was alone and out of touch with the Earth.

But if it must be, it must be.

He ensured that all the loose equipment in the craft was stowed away. Then he swam through to the descent module and sealed shut the hatch behind him.

He climbed into his pressure suit. He fixed his gloves and helmet in place. He made to close his visor.

He paused.

He clasped his hands on his lap, closed his eyes, and intoned, “Help us, God.” It was just as if his family was with him, here in the sphere of the Moon. Then he straightened up to begin his work.

He closed his helmet, and settled into the contoured couch at the centre of the descent module. He pulled his restraints around his body, adjusted them, and locked them in place.

Now, he need only wait for the computer to count down to the final burn.

Arkady sailed over the Moon’s North Pole. The flat sunlight picked up particles swimming along with the Soyuz — flakes of paint or insulation — and if he banged his fist on the wall a whole shoal of them would be born. They seemed to sparkle as they moved away from Soyuz, but some of them floated nearby, as if tracking a current through water.

Three, two, one.

There was no noise. Not even a vibration. Just a gentle, steady, push in the back.

Good engineering, he thought.

Soon it was over.

He had lost velocity, and the orbit of the Soyuz had become an ellipse. As he sailed around the Moon, he would come gradually lower, until — as he approached the South Pole, all of halfway around the Moon — he would reach his new orbit’s lowest point, which would graze the surface itself.

So he was committed. His only regret was that he would die alone, without so much as touching another human being again.

But then he would not be alone, on the Moon. Geena was there.

In the dark, the attitude system fired. He could hear the hollow rumble of the vernier rockets, like somebody dragging a chain across the hull of the ship. The Soyuz was automatically turning itself around, for it must come down nose-first. Through his portholes he could see flashes, a pinkish spray of particles from the reaction control nozzles, like sparks from a fire.

And then he flew into sunlight, without warning, as he had every two hours since entering this lunar orbit. As the light flooded over him, and the sun’s heat sank into the fabric of the ship, making the hull tick and expand, he felt a surge of renewal, of rebirth. He basked in the light, like a cat on a zavalinka, the earthen wall of a peasant’s house.

Coupled by the emergency hoses like Siamese twins, moving awkwardly, clumsily, constantly fearful of breaking their contact, ever aware of the way their time on the Moon’s surface was diminishing…

Thus, Henry and Geena laboured to collapse their shelter, their only home on the Moon, and to load up the old Apollo Rover with their survival gear.

When they were done the Rover was piled high with equipment. The collapsed shelter, a big pie-dish, was tied to the back by nylon rope.

“Like something out of The Beverly Hillbillies,” said Henry.

“I always hated that show.”

They clambered onto the Rover, and Geena pushed at the joystick.

The Rover lumbered forward.

It was a rocking and rolling ride, all the way to the rille complex. Every time it hit a mound or a depression or a crater rim — which was every few seconds — the Rover teetered precariously, obviously top-heavy.

Geena followed yesterday’s tracks, but today they rolled right past the point where they’d parked.

They approached the rim of a side rille, much smaller than Schröter’s Valley.

“That’s it,” Henry said. “Pull over.” Henry got out of the Rover even before they stopped, but his hoses yanked him back, and he tumbled back into his seat.

She rapped his helmet. “Do not do that again, asshole.”

“Sorry.”

They went through the complex and embarrassing ballet of getting themselves, as a joined pair, off the Rover.

Together, they walked to the rille. Geena held Henry’s hand, to ensure they didn’t separate too far. She couldn’t feel his hand, inside the thickness of his glove. It was difficult to Moonwalk, joined like this; they had to synchronize their loping.