Sas agreed, and they each set out. Don easily hopped ten meters, and it didn’t take more than digging with his boot’s toe to uncover more of the metal. He hopped another ten and again easily found metal, although it seemed a little deeper down this time. Ten more; metal again. A further ten and, although he had to dig through about a meter of dust to get to it, he found metal once more. Of course, because of the puny gravity, there was no danger of sinking into the dust, but the stuff that had been disturbed was now hanging in charcoallike clouds above the surface.
Although it had been Don’s plan to go by ten-meter increments, he was starting to think that such trifling hops might result in a lot of wasted time. He gave a more vigorous kick off the ground this time and sailed forward fifty-odd meters. And yet again he found smooth metal, although it was buried even deeper out here, and—
“Don!” Sas’ voice, shouting into his speaker. “I’ve found the edge!”
Don turned around and quickly flew across the 150 or so meters to where Sas was standing. The edge he’d uncovered was perfectly smooth. They both dug down around it with their gloved hands. It turned out the aluminum sheet was quite thin—no more than a centimeter. Don started working along one direction, and Sas along the other. They had to expose several meters of it before they noticed that the edge wasn’t straight. Rather, it was gently curved. After a few more minutes, it was apparent that they were working their way along the rim of a disk that was perhaps a kilometer in diameter.
But no—no, it wasn’t a disk. It was a dish, a great metal bowl, as if an entire crater had been lined with aluminum, and—
“Jesus,” said Don.
“What?” replied Sas.
“It’s an antenna dish.”
“Who could have built it?” asked Sas.
Don tipped his head up to look at Mars—but he couldn’t see Mars; they were on Deimos’ farside.
The farside! Of course!
“Sas—it’s a radio telescope!”
“Why would anyone put a radio telescope on the back side of Deimos?” asked Sas.
“Unless… oh, my. Oh, my.”
Don was nodding inside his space helmet. “It was built here for the same reason we want to build a radio telescope on the backside of Earth’s moon. Luna farside, with all those kilometers of rock between it and Earth, is the one place in the Solar System that’s shielded from the radio noise coming from human civilization…”
“And,” said Sas, “Deimos farside, with fifteen kilometers of rock between it and Mars, would be shielded from the radio noise coming from…” His voice actually cracked.
“…from Martian civilization.”
Sas and Don continued to search, hoping there would be more to the installation than just the giant dish, but soon enough Deimos’ rapid orbit caused the sun—only half the apparent diameter it was from Earth and giving off just one-quarter the heat—to sink below the horizon. Deimos took thirty hours and nineteen minutes to circle Mars; it would be almost fifteen hours before the sun rose on the tiny moon again.
“This is huge,” said Sas, when they were back inside the habitat. “This is gigantic.”
“A Martian civilization,” said Don. He couldn’t get enough of the phrase.
“There’s no other possibility, is there?”
Don thought about that. There had been a contingency plan for Apollo 11 in case it found Soviets already on the Moon—but NASA was no longer in a space race with anyone. “Well,” said Don, “it certainly wasn’t built by humans.”
“Zakarian and company are going to have a lot to look for on the surface,” said Sas.
Don shrugged a bit. “Maybe. Maybe not. There’s weather on Mars, including sandstorms that last for months. All the large-scale water-erosion features we see on Mars are at least a billion years old, judging by the amount of cratering overtop of them. That suggests that whatever Martian civilization might have once existed did so at least that long ago. In a billion years, wind erosion could have destroyed every trace of an ancient civilization down there.”
“Ah,” said Sas, grinning. “But not here! No air; no erosion to speak of. Just the odd micrometeoroid impact.” He paused. “That dish must have been here an awfully long time, to get buried under that much dust.”
Don smiled. “You know,” he said, “every space station humanity has ever been involved with has been inhabited by successive crews—Skylab, Mir, Alpha. One crew would go down; another would come up.”
Sas raised his eyebrows. “But there’s never been such a long hiatus between one crew leaving and the next one arriving.”
When they knew the sun would be up on Deimos farside, Don and Sas headed back to the site of the alien antenna dish. They had almost finished making their way around its perimeter when they found a spoke, projecting outward from the rim of the antenna.
They kept digging down, following it away from the dish, until—
“Allah-o-akbar!” exclaimed Sasim.
“God Almighty,” said Don.
The spoke led to a buried building, and—
Well, its inhabitants had been astronomers. It made sense that they’d have a glass roof, a clear ceiling through which they could look up at the stars.
As Don and Sas brushed away more and more dust, they were better able to see in through the roof. There was furniture inside, but none of it designed for human occupants: several bowl-shaped affairs that Don imagined were chairs, and low worktables, covered with square sheets of something that seemed to serve the same purpose as paper. Scattered about were opaque cylindrical units that looked like they might be for storage. And—
Slumped against the wall, at the far end—
It was incredible. Absolutely incredible.
A Martian, perfectly preserved for countless millennia. Either they had no such thing as bacteria leading to decay, or everything had been sterilized before coming to Deimos, or perhaps all the air had leaked out somehow, preserving the being in vacuum.
The former resident of the building was vaguely insectoid, with rusty exoskeletal armor, four arms, and two legs. In life, he would have walked proud and upright. His mandible was tripartite; his giant eyes, lidless behind crystal shells, were a soft, kind blue.
“Amazing,” said Sas softly. “Amazing.”
“There must be a way inside,” said Don, looking around. For all they knew from what they’d exposed of the transparent roof so far, the building might be no bigger than a single room. Still, it had been carved into the rocks of Deimos, so the air lock, if there was one, should be somewhere on the roof.
Don and Sas worked at clearing debris, and, after about twenty minutes, Don found what they were looking for. It was a transparent tube, like the one George Jetson shot up through, stretching between the glass roof and the floor. The tube had an opening in its circular walls at ground level, and a hatch up on the roof, forming a chamber that air could be pumped into or out of.
Any space station had lots of electrical parts, but doors were something sane engineers would make purely mechanical. After all, if the power went out, you didn’t want to be trapped inside or outside. It took Sas and Don a few minutes to work out the logic of the door mechanism—a central disk in the middle of the roof had to be depressed, then rotated counterclockwise. Once that was done, the rest of the hatch irised open, and the locking disk, attached by what looked like a plastic cord, dangled very loosely at one side.
Don glided down the tube first. He wasn’t able to open the inside door until Sas closed the upper lid; a safety interlock apparently prevented anyone from accidentally venting the habitat’s air out into space.
Still, it was immediately obvious to Don, once he was out of the air lock tube, that there was no air inside the habitat. The rigidity of his pressure suit didn’t change; no condensation ap-peared on his visor; there was no resistance to waving his arms vigorously. Doubtless there had been some air once, but, despite the safety precautions, it had all leaked out. Perhaps a small meteor had drilled through the roof at some point they hadn’t yet uncovered.