Aleksander Mironov hummed softly as he checked Jamie’s backpack. The rover’s airlock was crowded with just the two of them in it: Mironov in his fire-engine red hard suit, Jamie in his sky-blue, with a gray spare helmet to replace his meteorite-gouged original.

Mironov’s visor was up, and Jamie could see that the Russian was smiling as he clomped back into his view. Mironov’s face looked chunky, almost compressed in his helmet, as if stuffed into a container a half size too small. It was a broad-cheeked, snub-nosed face, slightly ruddy, sprinkled lightly with freckles, with pale blue eyes and eyebrows so fair they were barely visible.

"Gloves?" Mironov asked.

"Right here on my belt, Alex." Jamie tugged them on. Of all the equipment on the mission, the gloves were the most advanced piece of technology. Thin enough to be easily flexible and give the wearer a good feel for whatever he grasped, yet tough enough to protect the hands against the near vacuum of the Martian atmosphere.

"Visor down," Mironov said. Only after they had both sealed their helmets did he turn to the pumps and start them chugging.

"You look tired," the cosmonaut said over the suit-to-suit radio.

Surprised, Jamie said to the gold-tinted visor, "I feel okay."

"You were outside four hours yesterday, then you stayed up very late last night. You were outside all morning, and now you go again."

The pumps stopped. The indicator light turned red. Mironov pushed the hatch open.

"We’ve only got three days here," Jamie replied as they stepped through the hatch and down the short ladder to the rough, blackened ground. "We’ve got to make the most of them."

"Patel makes you feel guilty."

Jamie forgot himself and tried to shrug inside the suit. All he got for his effort was a fresh irritation under his armpit, where the suit chafed him.

"You must not drive yourself so hard," Mironov went on. "When you are tired you make mistakes. Mistakes can kill a man."

"I’ll be all right. The others are pushing just as hard," Jamie said.

"I gave them the same lecture," said the Russian. His voice sounded more disappointed than distressed.

"And?" Jamie asked.

Mironov pointed a gloved finger toward the butter yellow and dark green figures of Patel and Naguib. "They ignored me just as you are ignoring me."

Patel and Naguib were already chipping samples of the dark basaltic rock that spread as far as the eye could see. Old lava flow, Jamie knew. Pavonis Mons had erupted over and over again, red-hot magma flowing in all directions. How long ago? The samples they were taking would give them the answer. They had decided to spend these three precious days at the base of the volcano’s shield, collecting as many samples from as many different locations as possible. They would start to analyze them on the trek back to the base, they had agreed.

Yet none of the three scientists could resist testing the samples they had collected. Last night they had stayed up for hours, while Mironov reminded them of the mission schedule like an ineffectual camp counselor. They ran a dozen samples through the portable GC/ MS in the rover’s lab module.

The mass spectrometer told them that their samples were iron-rich basalts, no more than five hundred million years old, based on their ratio of potassium to argon.

"But the argon might have outgassed," Jamie warned. "Some of it may have escaped into the atmosphere."

"Much of it may be missing," Naguib agreed.

"Which means that the samples could be much older," said Jamie.

Patel, still refusing to meet Jamie’s eyes, said to the Egyptian, "We will run more definitive tests back at the base, where we can irradiate the samples in the power reactor."

Naguib nodded and said, "Yes. If the remote handling system is working. It was down…"

"Pete said he’d have it running by the time we got back," Jamie said.

"Astronaut Connors!" Patel almost snorted. "He spends all his time flying the RPV instead of attending to maintenance."

"Pete will have the remote handlers working by the time we get back," Jamie insisted.

Finally they folded down their bunks for sleep: Patel and Naguib on the uppers, Mironov and Jamie below. Jamie fell asleep quickly, only to be awakened by a whining, almost sobbing sound from above. One of them’s having a nightmare, he realized. He turned his face toward the curving wall of the rover and went back to sleep. His last conscious thought was that the metal skin of the vehicle felt cold; the freezing night of Mars waited outside, less than an inch away.

Over breakfast they had agreed that their best strategy was to work along the line of fissures and sinkholes that ran up one side of the volcano’s massive base. They would go as far as they could up the gentle slope of the shield, with Mironov driving the rover behind them so they would not exceed the safe walk-back distance specified in the mission regulations.

All three of these volcanoes sit astride this big fault line, Jamie said to himself as he laboriously chipped away at the tough black basalt. Looking back toward the rover, he saw Mironov planting another beacon into the ground. It was not easy work; this was real rock, not the compacted sands they had found around their domed base. The thin layer of reddish dust that covered the rock was easily scuffed away. Jamie wondered why the wind did not remove it entirely.

Inside his hard suit Jamie could not feel any wind, and there were no clouds in the salmon sky to show air movements. Yet the meteorology instruments on their beacons showed a fairly steady breeze of more than forty miles per hour running up the long gradual slope toward the volcano’s distant summit. At night the wind direction reversed to downslope and slowed to little more than twenty miles per hour.

Forty miles per hour would be a stiff gale on Earth, Jamie knew. But in the thin air of Mars there was no strength in the wind, not even enough to scour the last layer of sand off the rocks.

Jamie put his hands on his knees and let the suit’s fans cool him down for a while. His visor was starting to fog over from his exertion. He waited, scanning the barren rocky waste that stretched all around him. Dead rock, as rough and bare as the worst badlands he had ever seen in New Mexico. Blasted and pitted by meteor craters, some as big as a football field, most nothing more than the dent a hammer might make on the hood of a car. There were cracks in the solidified lava, vents and fissures that twisted from one crater pit to another. The ground rose almost imperceptibly toward the volcano’s high caldera, so far away that it was well over the horizon.

Strangely, not so many rocks were scattered around. The molten basalt must have pushed them downslope. Jamie pictured the black rocky field on which he stood as it must once have been: a broad surging stream of red-hot lava spewing from those vents to flow sluggishly down toward the plain, melting or bulldozing the rocks in its path.

Heat must be coming up from the interior along this fault line, Jamie reasoned. Molten magma flowing time and time again, building these big cones, spilling out to form the shields. Then what about Olympus Mons, some fifteen hundred kilometers to the northwest? It’s not sitting on a fault, not that we can see. But it’s probably younger than these three beauties. Could there be a hot spot down below that built Pavonis and its two companions, then migrated northwest to build Olympus?

Jamie realized his back ached from stooping awkwardly in the cumbersome suit. He straightened up, wondering, Does Mars have plate tectonics, like Earth? Wouldn’t think so, the planet’s so small that its core can’t possibly have enough heat energy to move whole continents of mantle rock. But there was enough heat energy to build these volcanoes. Where did it come from? Is it still flowing?