“Which part of Earth would you like to visit?” I asked.
“The deserts,” he said.
“Not the rain forests?”
He grinned behind his face plate. “Better fossils in dry places.”
We climbed into the lab, destatted and sucked off our dust, and ate soup in the cramped kitchen. We had barely finished our cups when a shrill alarm came from our slates and the lab’s com.
Emergency displays automatically flickered before us. The distinctive masculine voice of Security Mars spoke. “A cyclonic low-pressure system in Arcadia Planitia has produced a force ten pressure surge moving southwest at eight-hundred and thirty kiphs. All stations and teams between Alba Patera in the north and Gordii Dorsum in the south are advised to take emergency precautions.” Graphs of the surge and a low-orbit satellite picture appeared, superimposed on a projected map. The surge resembled a thin curving smudge of charcoal drawn over the terrain. Its numbers were impressive: two thousand kilometers long, following a great-circle contour, absolutely clear atmosphere ahead and murk behind, with a dark pressure curl along its central axis. The surge had already reached a pressure of one third of a bar — almost fifty times normal.
First seen in the twentieth in early Viking photographs, surges were the worst Mars had to offer. Induced by supersonic shock-waves, the high-pressure curls were unique to Mars, with its thin atmosphere, cold days, and even colder nights. Here, the borders between night and day could become weather fronts in themselves. There were no oceans, as on Earth, to liberate heat slowly and mediate between ground and sky… At nightfall, the ground cooled quickly, and the thin air above the ground descended dramatically, only to warm and rise rapidly at daybreak. Most of the time, the worst weather patterns Mars could muster were the thin, high-wind-speed storms familiar to all. These spread across basins and plains, covering everything with dust but producing only slight changes in barometric pressure.
Under the right conditions, however, and in the proper terrain — crossing the plains of the northern lowlands, in mid-morning or late evening — winds generated by the terminator could exceed the speed of sound, compressing the air to as much as a hundred times its normal pressure of four to seven millibars. Passing from the plains to rough terrain, the shock-wave could be given a deft horizontal spin, producing a super-dense rolling curl that picked up huge volumes of fine clay, and sand, and at peak, even pebbles and rocks.
Ilya and I immediately suited and set to work lowering the mobile lab and shooting anchors deep into the soil and rock beneath. We slung cables over the lab from anchor to anchor, then pulled folded plastic foils from the boot in the lab’s round stern, stretching them from the ground and fastening them to the lab’s sides to make a wind ramp. The foil stiffened quickly into the proper shape. It would also function as a shield against debris.
“We’ve got about ten minutes,” I said. We both looked into the arroyo at the slab-sided shed with its precious specimens, a tin shanty that would love to fly.
“There’s a spare tarp and foil,” Ilya said. “We can rig it in six minutes — or we can get inside.”
“Rig it,” I said. He grabbed my hand and squeezed it.
We worked quickly. Surges could be terribly destructive even to a buried station if it was unprepared. The center of a surge’s curl could compress to as much as half a bar, a rolling-pin of tight-packed air moving at well over eight hundred kiphs; and the farther a surge rolled, the tighter it packed, until it blew itself out against a volcano or plateau and spread dust and cyclones over half of Mars.
We stiffened the shed’s foil and kicked the tarp pegs. All was firm. We ran for the lab and sealed the flap behind us. A little excavator clambered up from a fresh-dug trench under the lab’s cylindrical body and fastened itself to its receptacle in the bottom of the lab. We crawled into the trench and spread our personnel foils. The foils undulated, stiffened, and glued themselves to the edges of the trench.
Ilya switched on a torch and shined it in our faces. We lay in the coffin-shaped ditch, with two layers of foil and the ponderous mobile lab over our heads, hands tight-clenched.
Outside: a horrid empty silence. Even the rock was quiet; the surge was still dozens of kilometers away. Ilya removed his slate from his utility belt and instructed the mobile lab’s roof camera to show us what was happening. To the northwest, all was dark gray shot through with streaks of brown.
“Are we cozy?” he asked. Our helmet radios whined faintly, we lay so close together.
“Snug as bunnies in a pot,” I said, teeth clenched.
“I’m sorry I got you into this, Casseia…”
I couldn’t clamp my hand over his mouth, but I made the gesture against his helmet anyway. “Shh,” I said. “Tell me a story.”
Ilya excelled at making up fairy tales on the spur of the moment. “Now?” he asked.
“Please.”
“Long ago,” he began, voice husky, “and long after now, two rabbits dug a hole in the farmer’s garden and ate through all of his water lines…”
I closed my eyes, listening.
Our helmets pressed against the rocks and each other. Before Ilya had finished the story, I laid my hand against the bottom of the ditch, palm flat to pick up vibrations. The line of dust and compressed atmosphere to the west stretched inky-black and very close. It began to obscure the horizon. Only seconds now…
All around, through the rocks, we heard a low grumbling, then a distinct, rhythmic pounding. “There it is,” I said. “Plains buffalo.” We had all seen Terrie Westerns.
Ilya placed his hand over mine. “Freight trains,” he said. “Hundreds of them.”
I began to shiver. “Have you been through one of these?” I asked.
“When I was a kid,” he said. “In a station.”
“Anybody hurt?”
He shook his head. “Small one. Only a quarter of a bar. Made a lot of noise when it went over.”
“What does it sound like when it goes over?”
He was about to tell me when I heard for myself. The sound started out ghostly — the sibilant patient whine of a strong Martian wind, audible through our helmets even in the trench, backed by the staccato of pebbles and dust striking against the foils and tarps. The blackness seemed to leap over the land.
I felt pressure in my ears, thin fingers pushing into my head. I opened my eyes to slits — my eyelids had pressed themselves tight shut instinctively — to see Ilya. He lay on his back, shoulder wedged against the side of the trench, staring up, eyes searching.
“This is going to be a bad one,” he said. “I’ll finish the story later, okay?”
“Okay. But don’t forget.” I shut my eyes again.
For a moment, the surge sounded like huge drums. A thin shriek descended into a monstrous, horrifying bellow. I thought of a ravening god marching over the land, Mars itself, god of war, furious and implacable, searching for things that might be frightened, things that might die.
The pressure suit loosened around me, then clung tight to my skin. A sharp pain in my ears made me screw up my face and groan. The torch fell between us. Ilya grabbed it again, shined it on his face, shook his head, face slick with tears, and held me tightly. I could feel his heart through the suits.
The vibration of the trench walls stopped. We lay for a moment, waiting for it to begin again. I started to get up, pushing against the tarp, frantic to see daylight — but Ilya grabbed my shoulder and pressed me down. I could not hear very well. The torch illuminated his face; he was trying to mouth words to me. Somehow I understood through my fear — rocks and dust would be falling outside. We might be killed by rocks falling from thousands of meters in the wake of the surge, striking at eighty or ninety meters per second. I pressed myself against him, mind racing, grimacing at the pain.