Mars rotates about its axis in almost the same time that Earth does. A day on Earth is 23 hours, 56 minutes, and 4.09 seconds long. A day on Mars is only slightly longer: 24 hours, 37 minutes, and 22.7 seconds.

To avoid confusion, space explorers refer to the Martian day as a "sol." In one Martian year there are 669 sols, plus an untidy fourteen hours, forty-six minutes, and twelve seconds.

Is there life on Mars?

That question has haunted the human psyche for centuries. It is the primary force behind our drive to reach the red planet. We want to see for ourselves if life can exist there.

Or once did.

Or does now.

The first thing the scientists did, after their little arrival speeches, was collect contingency samples of the Martian rocks, soil, and atmosphere.

Just in case a sudden emergency forced them to scramble into their landing/ascent vehicle and blast back into orbit around the planet, they spent their first two hours on the surface stuffing rocks and soil samples into airtight cases and filling vials with whiffs of air taken from ground level on up to ten meters, the latter obtained with the use of a gangling titanium pole.

Meanwhile, the construction robot trundled across the rocky ground out to the three unmanned cargo carriers that had landed the previous day, scattered over a two-kilometer-wide radius from their nominal landing site. Like an oversized mechanical ant, the robot busily hauled their cargos back to the inflated dome that would be home to the explorers for the next eight weeks.

Mikhail Andreivitch Vosnesensky, veteran of a dozen space missions, sat up in the cockpit in the commander’s seat, one eye on the scientists and the other on the mission schedule. Beside him, Pete Connors monitored the robot and conversed with the expedition command in orbit around the planet. Although both men stayed in their hard suits, ready to dash outside if an emergency required their help, they had taken their helmets off.

Connors switched off the radio and turned to the Russian. "The guys in orbit confirm that we landed only a hundred thirty meters from our nominal target spot. They send their congratulations."

Vosnesensky offered a rare smile. "It would have been closer, but the boulders were too big farther south."

"You did a damned good job," said Connors. "Kaliningrad will be pleased." His voice was a rich baritone, trained in church choirs. The American had a long, almost horsey face with a complexion the color of milk chocolate and large sorrowful brown eyes rimmed with red His hair was cropped militarily short, showing the distinct vee of a widow’s peak.

"You know what the old pilots say," Vosnesensky replied.

Connors chuckled. "Any landing you can walk away from is a good landing."

"All systems are working. We are on schedule." It was Vosnesensky’s way of making light of his skillful landing. The Russian did not trust flattery, even from a man he had worked with for nearly four years. A scowl was the normal expression on his broad, beefy face. His sky-blue eyes always looked suspicious.

"Yeah. And now the second team has to land where we are. Wonder how good Mironov and my old buddy Abell will be?"

"Mironov is very good. An excellent pilot. He could land on our roof, if he wanted to."

Connors laughed, light and easy. "Now that would cause a helluva problem, wouldn’t it?

Vosnesensky made his lips curl upward, but it obviously took an effort.

The scientists stored their contingency samples inside the airlock section of the L/AV. In an emergency, the airlock section and the cockpit atop it would lift off the ground. The lower half of the lander — the cargo bays and aerobrake — would remain on Mars. Even if one or more of the explorers were left behind, the precious samples would make it to the expedition spacecraft riding in orbit and then back to the scientists waiting on Earth.

That first chore completed to Vosnesensky’s satisfaction, he ordered the team to move supplies into the dome. They hurried to beat the oddly tiny sun as it got close to the western horizon. The construction vehicle towed the heavy pallets of equipment, while the explorers performed feats of seemingly superhuman strength, lifting man-tall green cylinders of oxygen tanks and bulky crates that would have weighed hundreds of pounds on Earth.

Sweating like a laborer inside his pressurized hard suit, Jamie smiled bitterly at the thought that the first task of the first explorers on Mars was to toil like coolies, grunting and lifting for hours in mindless drudgery. The public-relations statements and TV pictures make it all look so damned easy, he thought. Nobody ever watches a scientist at work — especially when he’s doing dog labor.

Neither he nor the others paid any special attention to their low-gravity strength. Over the nine-plus months of their flight from Earth their spacecraft had spun on a five-kilometer-long tether to simulate a feeling of weight, since prolonged periods in zero gravity weakened muscles dangerously and demineralized bones. Their artificial gravity began at a normal Earthly one g, then was slowly reduced during the months of their flight to the Martian value of roughly one-third g. Now, on the surface of Mars, they could walk normally yet still lift enormous weights with their Earth-evolved muscles.

At the end of their long, exhausting day they moved at last inside the inflated dome. The tiny sun was turning the sky flame-red and the temperature outside was already fifty below zero.

The dome was filled with breathable air at normal Earth pressure and temperature, according to the gauges. The thermometer read precisely twenty-one degrees Celsius: sixty-nine point eight degrees Fahrenheit.

The six of them were still inside their pressurized hard suits, however, and would stay in them until Vosnesensky decided it was safe to breathe the dome’s air. Jamie’s suit felt heavy against his shoulders. It no longer had that "new car" odor of clean plastic and untouched fabric; it smelled of sweat and machine oil. The backpack regenerator replaced carbon dioxide with breathable oxygen, but the filters and miniature fans inside the suit could not remove all of the odors that accumulated from strenuous work.

"Now comes the moment of truth," he heard Ilona Malater’s husky voice, sounding sexy — or maybe just tired.

Vosnesensky had spent the past few hours checking the dome for leaks, monitoring the air pressure and composition, fussing over the life-support pumps and heaters grouped together in the center of the hardened plastic flooring. One by one, the others slowly drifted to him, clumping in their thick boots, waiting for him to give the order they all awaited with a strange mixture of eagerness and dread.

Like it or not, Vosnesensky was their team leader, and years of training had drilled them to obey their leader’s orders without a thought for his nationality. Everything they did on this dangerously different world would be carried out according to rules and regulations painstakingly developed on Earth. Vosnesensky’s first and most important task was to see that those rules and regulations were carried out here on Mars.

Now the Russian turned from the gently humming air-circulation fans and the row of backup oxygen tanks to see that his five team members had gathered around him. It was difficult to make out his face through the helmet visor, impossible to read his expression. In his barely accented American English he said, "All the gauges are in the normal range. It appears safe to get out of our suits."

Jamie recalled a physicist at Albuquerque, frustrated over an experiment that refused to work right, telling him, "All of physics boils down to reading a goddam dial on a goddam gauge."