“A true giant leap,” said Sasim, over the radio. “Beats all heck out of a small step.”
Don smiled, although he knew he was too far away for Sasim to see him do that. The jump had been exhilarating. “Maybe this station isn’t going to be so bad after all.”
“I’ve got an idea,” said Sasim, as they continued to work converting the fuel tank into a habitat. “We could call this place Asaph Hall.”
“That’s the name of our spaceship,” said Don, perplexed.
“Well, yes and no. Our ship is called Asaph Hall, after the guy who discovered the moons of Mars. And when you refer to a ship, you write the name in italics. But this whole station could be Asaph Hall—’hall,’ like in a building, get it?—all in roman type.”
“That’s a pretty picayune distinction,” said Don, unfolding an articulated section divider that had been stored for the out-ward journey. “It’ll get confusing.”
Sas frowned. “Maybe you’re right.”
“Don’t worry. We’ll think of something.”
It took several days to finish the conversion of the empty fuel tank into the habitat, even though all the fixtures were designed for easy assembly. During the process, Don and Sasim had slept in their spaceship’s command module, but at last the habitat was ready for them to move in. And although it was roomy—bigger than Skylab or Mir—Don was finally beginning to appreciate the wisdom of making an entire moonlet into a space station. He could see how being confined to just the habitat would have gotten claustrophobic after a while, if he and Sas didn’t have the rest of Deimos to roam over.
And roam over it they did. It only took a dozen leaps to circumnavigate their little—well, it wasn’t a globe; the technical name for Deimos’ shape was a triaxial ellipsoid. It was a lot of fun leaping around Deimos—and, despite the low gravity, it was actually excellent exercise, too. Up, up, up, that brief magical moment during which you felt suspended, at one with the cosmos, and then gently, oh so gently, sliding down out of the sky.
Don and Sas were approaching the line that separated Deimos’ nearside—the part of the moon that always faced toward Mars—from its farside. Like the blooded horn of some great beast, the now-crescent Mars stretched from Deimos’ smooth surface up toward the zenith. One more leap, and—
Yup, there it went: the Red Planet disappearing behind the horizon. With its glare gone from the sky, Don tried to find Earth. He oriented himself with Ursa Major, found the zodiac, scanned along, and there it was, a brilliant blue point of light, right in the heart of Scorpius, not far from red Antares, the rival of Mars.
Sas, Don had noticed, had a funny habit of bending his knees when he contacted the surface. It wasn’t as if there was any real impact to absorb—it was just a bit of theater —and it made Don smile. Don’s space suit was a sort of mustard color, a nice contrast with Sas’. The dark ground loomed closer and closer to him, and—
There wasn’t enough speed with contact to make any sort of sound that might be conducted through Don’s boots. And yet, still, as his soles touched Deimos, something felt strange this time, just different enough from every other landing Don had made so far to pique his curiosity.
He’d raised up a fair bit of dust, and it took him a few seconds to realize exactly what had happened. His foot hadn’t hit crumbly regolith. It had hit something unyielding.
Something smooth.
Don did a gentle backflip, landing upside down on his gloved hands. He used his right one to brush away dust.
“Sas!” Don called into his helmet mike. “Come here!”
Sasim did a long jump, bringing him close to where Don was. Another small hop brought him right up to Don. “What’s up?” asked Sas—perhaps a joking reference to Don’s current odd posture.
Don used his fingertips to gently flip himself back into a normal orientation. “Have a look.”
Sas tipped over until he was more or less hovering just above the surface. “What the heck is that?” he said.
“I’m not sure,” said Don. “But it looks like polished metal.”
Don and Sas brushed dust away for more than an hour, and were still exposing new metal. It was indeed manufactured—it looked to be anodized aluminum. “Maybe it’s part of the Viking orbiter, or one of those Mars missions like Mars Polar Lander that went astray,” said Don, sounding dubious even to himself.
“Maybe,” said Sas. “But it’s awfully big…”
“Still no sign of an edge,” said Don. “Maybe we should try another approach. Let’s each go ten meters away, dig down, and see if the sheet is there under the surface. If it is, go on another ten meters, and try again. Keep going until we come to the edge. You go leading; I’ll go trailing.” On any tidally locked satellite, “leading” was toward the leading hemisphere, the one that faced forward into the direction of orbital motion; trailing was the opposite way.
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.