Free Marsquake! by Brad Strickland, THOMAS E. FULLER

creatures coming up onto the beach is a common pattern on Earth. Might be the same on Mars. Could be that most of the fossils would be on the edges of the water, not in the depths.”
    Sean said, “Depths is right. Have you noticed the air pressure down here? We could walk around with our suits off.”
    “Except we wouldn’t be able to breathe. The pressure’s almost the same as near the top of Mount Evereston Earth—but it’s all CO2. You’d be able to take about five breaths of that before you asphyxiated.”
    “We turn back tomorrow,” Sean said. “I think Miles would like to stay behind, to tell you the truth. He’s still wanting to find more of his bony little buddies.”
    “He can come back later with his team,” Jenny said. She sniffed, taking a bigger bite of her ration bar than Sean ever dared to take of his own. “You know, Pavel Rormer’s doing better than I expected.”
    Sean made a so-what gesture. “He’s got atmospheric testing to interest him. As long as he’s occupied, he’s not spouting nonsense. I don’t see him going out of his way to be chummy with anyone else, though.”
    “No, he’s not friendly with anybody. But at least he’s not fighting.”
    Though neither of them commented on it, more than the pressure was rising. The air temperature was heading up too. On the surface, even at noon the thermometer never registered more than ten below zero during the winter. In the lava tunnel, warmth increased as the exploration team went farther belowthe surface, until it leveled off at 14.6 degrees Celsius—the temperature of a cool spring day on Earth, but very balmy for Mars, and well above freezing. That brought a bit of a disadvantage though, because while the pressure suits could be heated to counteract the surface cold, they had a harder time dissipating the heat buildup. Sean thought that sometimes it felt as if he were working in a sauna, a portable sauna that he carried around with him.
    Still, the expedition was going well. Everyone was busy, Sean reflected the next day, and no one was fighting. That was the key. By this point everyone in the expedition was laden down with samples of minerals. Sean was grateful that all he and Jenny were taking was their series of pictures—and they didn’t weigh anything.
    For about the third or fourth time in their journey, they came into yet another enormous open chamber, this one more than a hundred meters from floor to ceiling. Powerful lights cutting through the gloom showed that the cavern’s upper reaches dripped withstalactites—long, pointed fingers of varicolored stone. As the water levels had dropped, these had been formed by mineral-rich water seeping down from the far distant surface. Each oozing water droplet had evaporated, leaving behind a minute trace of the minerals it carried, and so the stalactites had grown, a molecular layer at a time. Some of them now were ten meters long, great stone daggers pointing downward. Sean had a dizzy kind of feeling: looking up at the stalactites was a bit like hovering in the air above some ancient medieval cathedral on Earth and looking down at its spires.
    The sand underfoot lay in a strange, gently rippled pattern. No waves should have disturbed the underground sea—no winds ever blew down here to stir them up. Still, somehow the water had flowed, and it had left behind graceful traces of its passage. Here, as in many stretches of the tunnel, the sand had hardened, cemented into place by the minerals that the drying sea had left behind. It was sandstone now, extraordinarily fine grained, looking as if you could stir it with a toe. Miles was edging around the cavern’speriphery, his eyes keen on the sand underfoot. Sean knew that he dearly wanted to find a second fossil, and he wished the man luck.
    “This is odd,” Jenny said. They had switched to a private frequency to talk about the photos they were recording, though their helmet receivers were set to pick up the main frequency in