shifted from pockets of complete clarity, with thick yellow clouds like thunderheads sailing north with them, to complete obscurity, all the window surfaces streaming with dust that wormed and spun like a particularly unpleasant screensaver. Even at twelve millibars the blast of the wind was tossing the dirigible about; up in the cockpit Arkady was cursing the autopilot’s insufficiency. “Reprogram it,” Nadia called forward, and then remembered all his sadistic simulations on the Ares, and laughed out loud: “Problem run! Problem run!” She laughed again at his shouted curses, and went back to work. Arkady yelled back information from Ann. The dust was extremely fine, average particle size about 2.5 microns; total column mass about 1−3 grams per cm−2, pretty evenly distributed from top to bottom of the column. That wasn’t so bad; drop it on the ground and it would be a really thin layer, which was consistent with what they had seen on the oldest freight drops at Underhill.
When she had prepped all the solar panels she banged down the passageway to the cockpit. “Ann says the winds will be slowest close to the ground,” Arkady said.
“Good. We need to land to get the panels outside.”
So that afternoon they descended blind, and let the anchor drag until it hooked and held. The wind here was slower, but even so Nadia’s descent in the sling was harrowing. Down and down into rushing clouds of yellow dust, swinging back and forth … and there it was right under her boots, the ground! She hit and dragged to a halt. Once out of the sling she found herself leaning into the wind; thin as it was it still struck like blows, and her old feeling of hollowness was extreme. Visibility billowed back and forth in waves, and the dust flew past so fast it was disorienting—on Earth a wind that fast would simply pick you up and throw you, like a broom-straw in a tornado.
But here you could hold your ground, if only just. Arkady had been slowly winching the dirigible down on the anchor line, and now it bulked over her like a green roof. It was weirdly dark underneath it. She unreeled the wires out to the wingtip turboprops, taped them to the dirigible and crimped them to the contacts inside, working fast to try to reduce their exposure to dust, and to get out from under the Arrowhead, which was bouncing on the wind. With difficulty she drilled holes in the bottom of the gondola fuselage, and attached ten solar panels with screws. As she was taping the wiring from these to the plastic fuselage, the whole dirigible dropped so fast that she had to collapse onto her face, her whole body spread-eagled on the cold ground, the drill a hard lump under her stomach. “Shit!” she shouted. “What’s wrong?” Arkady cried over the intercom. “Nothing,” she said, jumping up and taping faster than ever. “Fucking thing—it’s like working on a trampoline—” Then as she was finishing the wind picked up strength yet again, and she had to crawl back down to the bomb bay, her breath rasping in and out of her.
“The damn thing almost crushed me!” she shouted forward to Arkady when she had her helmet off. While he worked to unhook the anchor she staggered around the interior of the gondola, picking up things that they wouldn’t need and taking them into the bomb bay: a lamp, one of the mattresses, most of the cooking utensils and dinnerware, some books, all the rock samples. In they went, and she jettisoned them happily. If some traveler ever came upon the resulting pile of stuff, she thought, they would really wonder what the hell had happened.
They had to run both props full out to get the anchor unhooked, and when they succeeded they were off and flying like a leaf in November. They kept the props on full, to gain altitude as fast as possible; there were some small volcanoes between Olympus and Tharsis, and Arkady wanted to pass several hundred meters over them. The radar screen showed Ascraeus Mons falling steadily behind. When they were well north of it they could turn east, and try to chart a course around the northern flank of Tharsis, and then down to Underhill.
But as the long hours passed they found that the wind was rushing down the north slope of Tharsis, across their bow, so that even when running full power toward the southeast, they were still only moving