After that winds blew from the south for several days. They caught a glimpse of Cassini, another great old crater, and passed over hundreds of smaller ones. They dropped several windmills per day, but the flight was giving them a stronger sense of the size of the planet, and the project began to seem like a joke, as if they flew over Antarctica and tried to melt the ice by setting down a number of camping stoves. “You’d have to drop millions to make any difference,” Nadia said as they climbed up from another drop.
“True,” Arkady said. “But Sax would like to drop millions. He’s got an automated assembly line that will just keep churning them out, it’s only distribution that is a problem. And besides, it’s just one part of the campaign he has in mind.” He gestured back toward the last arc of Cassini, inscribing the whole northwest. “Sax would like to bang out a few more holes like that one. Capture some icy moonlets from Saturn, or from the asteroid belt if he can find any, and push them back and smash them into Mars. Make hot craters, melt the permafrost— they’d be like oases.”
“Dry oases, wouldn’t they be? You’d lose most of the ice on entry, and have the rest disappear on contact.”
“Sure, but we can use more water vapor in the air.”
“But it wouldn’t just vaporize, it would break into its constituent atoms.”
“Some of it. But hydrogen and oxygen, we could use more of both.”
“So you’re bringing hydrogen and oxygen from Saturn? Come on, there’s lots of both here already! You could just break down some of the ice.”
“Well, it’s just one of his ideas.”
“I can’t wait to hear what Ann says to that.” She sighed, thought about it. “The thing to do, I suppose, would be to graze an ice asteroid through the atmosphere, as if trying to aerobrake it. That would burn it up without breaking the molecules apart. You’d get water vapor in the atmosphere, which would help, but you wouldn’t be bombing the surface with explosions as big as a hundred hydrogen bombs going off all at once.”
Arkady nodded. “Good idea! You should tell Sax.”
“You tell him.”
East of Cassini the terrain grew rougher than ever. This was some of the oldest surface on the planet, cratered to saturation in the earliest years of torrential bombardment. A hellish age, the Noachian, you could see that in the landscape. No Man’s Land from a titanic trench war, the sight of it induced a kind of numbness after a while, a cosmological shell shock.
They floated on, east, northeast, southeast, south, northeast, west, east, east. They finally came to the end of Xanthe, and began to descend the long slope of Syrtis Major Planitia. This was a lava plain, much less densely cratered than Xanthe. The land sloped down and down, until finally they drifted over a smooth-floored basin: Isidis Planitia, one of the lowest points on Mars. It was the essence of the northern hemisphere, and after the southern highlands it seemed especially smooth and flat and low. And it too was a very large region. There really was a lot of land on Mars.
Then one morning when they lofted up to cruising altitude, a trio of peaks rose over the eastern horizon. They had come to Elysium, the only other Tharsislike “bulge continent” that the planet had. Elysium was a much smaller bulge than Tharsis, but it was still big, a high continent, 1,000 kilometers long and ten kilometers taller than the surrounding terrain. As with Tharsis, it was ringed by patches of fractured land, crack systems caused by the uplift. They flew over the westernmost of these crack systems, Hephaestus Fossae, and found the area an unearthly sight: five long deep parallel canyons, like claw marks in the bedrock. Elysium loomed beyond, a saddleback in shape, Elysium Mons and Hecates Tholus rearing at each end of a long spine range, 5,000 meters higher than the bulge they punctuated: an awesome sight. Everything about Elysium was so much bigger than anything Nadia and Arkady had seen so far that as the dirigible floated toward the range, the two were speechless for minutes at a time. They sat in their seats, watching it all float slowly toward them. When they did speak, it was just thinking aloud: “Looks like the Karakoram,” Arkady said. “Desert Himalayas. Except these are so simple. Those volcanoes look like Fuji. Maybe people will hike up them someday in pilgrimages.”
Nadia said, “These are so big, it’s hard to imagine what the Tharsis volcanoes will look like. Aren’t the Tharsis volcanoes twice as big as these?”
“At least. It does look like Fuji, don’t you think?”
“No, it’s a lot less steep. Why, did you ever see Fuji?”
“No.”