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Vijay, ready to offer his hand if she stumbled on the rocks scattered across the ground. His geologist’s eye took in the area. This must be a really old impact crater, he told himself. Weathering on Mars takes eons, and this rim is almost eroded down to the level of the sand floor. Must have been a big hit, from the size of the basin. What’s left of it.
    Trumball was already down in the shadows, on his knees, carefully scraping the fragile, paper-thin coating of ice into an open sample container.
    “It’s water ice, all right,” he was saying over the suit-to-suit frequency as they approached him. “Same isotopic composition as the ice at the north pole, I bet. Stuff sublimes into vapor up there and the atmosphere transports it down toward the equator.”
    Vijay pointed with a gloved finger. “It’s melting where the sun is hitting it.”
    “Subliming,” Trumball said without looking up from his work. “It doesn’t melt, it sublimes.”
    “Goes from ice to vapor,” Jamie explained, “with no liquid phase in between.”
    “I understand,” she replied.
    “The atmosphere’s so thin, liquid water evaporates immediately.”
    “Yes, I know,” she said, with a slight edge in her voice.
    Trumball snapped the container shut and inserted it into his sample case. “This’ll help us nail down the global circulation of the atmosphere.”
    “Will this water be carbonated, too?”
    Closing the plastic box and climbing to his feet, Trumball said, “Sure. Just like the water from the permafrost underground. Martian Perrier, loaded with carbon dioxide.”
    Jamie started them back toward the base, feeling left out of the conversation but not knowing how to jump in without making it seem obvious that he was competing with the younger man.
    “Life has the same needs here as on Earth,” Vijay was saying.
    “Why not?” Trumball replied, waving his free hand. “It’s all the same, basically: DNA, proteins—same on both planets.”
    “But there are differences,” Jamie said. “Martian DNA has the same double-helix structure as ours, but the base pairs are different chemicals.”
    ”Yeah, sure. And Martian proteins have a few different amino acids in ‘em. But they still need water.”
    They had reached the crest of the rim rock. Jamie could see the camera atop its high skinny pole peering at them.
    Reluctantly, he said, “We’d better get back to the dome and help finish the unloading.”
    She answered, “Yes, I suppose we should.”
    Jamie couldn’t see Trumball’s face behind the heavily tinted visor of his helmet, but he heard the younger man laugh.
    Hefting his container box, Trumball said, “Well, some of us have important work to do. Have fun playing stevedores.”
    And he loped across the rock-strewn ground toward the base shelter, leaving Jamie and Shektar standing on the rim of the ancient crater.

 
VIRTUAL TOUR: SOL 1
     
    LATER THAT AFTERNOON, C. DEXTER TRUMBALL WAS STILL EXCITED AS HE clicked the two miniaturized VR cameras into the slots just above his visor. They were slaved to the movements of his eyes, if the electronics rig worked right. Together with the molecular-thin data gloves he had already wormed over his spacesuit gloves, he would be able to show the millions of viewers on Earth whatever he himself saw or touched.
    Briefly he looked back at the rest of the crew, now carrying crates and bulky canisters through the dome’s airlock. They would spend the rest of the day setting up equipment and making the dome livable. Trumball’s job was to entertain the people back home who were helping to pay for this expedition.
    The first expedition to Mars had been run by national governments and had cost nearly a quarter-trillion dollar. This second expedition was financed mostly by private sources and cost less than a tenth as much.
    Of course, the six years between the two missions had seen the advent of Clipperships, reusable spacecraft that brought down the cost of flying into orbit from