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runners are straight. If we let gravity lead the sled and we don't interfere, we're guaranteed to travel in a straight line."

"Neat trick," Tolland yelled. "Wish there were something like that for the open sea."

This IS the open sea, Rachel thought, picturing the ocean beneath them. For a split second, the most distant flame caught her attention. It had disappeared, as if the light had been blotted out by a passing form. A moment later, though, the light reappeared. Rachel felt a sudden uneasiness. "Norah," she yelled over the wind, "did you say there were polar bears up here?"

The glaciologist was preparing a final flare and either did not hear or was ignoring her.

"Polar bears," Tolland yelled, "eat seals. They only attack humans when we invade their space."

"But this is polar bear country, right?" Rachel could never remember which pole had bears and which had penguins.

"Yeah," Tolland shouted back. "Polar bears actually give the Arctic its name. Arktos is Greek for bear."

Terrific. Rachel gazed nervously into the dark.

"Antarctica has no polar bears," Tolland said. "So they call it Anti-arktos."

"Thanks, Mike," Rachel yelled. "Enough talk of polar bears."

He laughed. "Right. Sorry."

Norah pressed a final flare into the snow. As before, the four of them were engulfed in a reddish glow, looking bloated in their black weather suits. Beyond the circle of light emanating from the flare, the rest of the world became totally invisible, a circular shroud of blackness engulfing them.

As Rachel and the others looked on, Norah planted her feet and used careful overhand motions to reel the sled several yards back up the slope to where they were standing. Then, keeping the rope taut, she crouched and manually activated the sled's talon brakes-four angled spikes that dug into the ice to keep the sled stationary. That done, she stood up and brushed herself off, the rope around her waist falling slack.

"All right," Norah shouted. "Time to go to work."

The glaciologist circled to the downwind end of the sled and began unfastening the butterfly eyelets holding the protective canvas over the gear. Rachel, feeling like she had been a little hard on Norah, moved to help by unfastening the rear of the flap.

"Jesus, NO!" Norah yelled, her head snapping up. "Don't ever do that!"

Rachel recoiled, confused.

"Never unfasten the upwind side!" Norah said. "You'll create a wind sock! This sled would have taken off like an umbrella in a wind tunnel!"

Rachel backed off. "I'm sorry. I... "

She glared. "You and space boy shouldn't be out here."

None of us should, Rachel thought.

Amateurs, Norah seethed, cursing the administrator's insistence on sending Corky and Sexton along. These clowns are going to get someone killed out here. The last thing Norah wanted right now was to play baby-sitter.

"Mike," she said, "I need help lifting the GPR off the sled."

Tolland helped her unpack the Ground Penetrating Radar and position it on the ice. The instrument looked like three miniature snowplow blades that had been affixed in parallel to an aluminum frame. The entire device was no more than a yard long and was connected by cables to a current attenuator and a marine battery on the sled.

"That's radar?" Corky asked, yelling over the wind.

Norah nodded in silence. Ground Penetrating Radar was far more equipped to see brine ice than PODS was. The GPR transmitter sent pulses of electromagnetic energy through the ice, and the pulses bounced differently off substances of differing crystal structure. Pure freshwater froze in a flat, shingled lattice. However, seawater froze in more of a meshed or forked lattice on account of its sodium content, causing the GPR pulses to bounce back erratically, greatly diminishing the number of reflections.

Norah powered up the machine. "I'll be taking a kind of echo-location cross-sectional image of the ice sheet around the extraction pit," she yelled. "The machine's internal software will render a cross section of the glacier and then print it out. Any sea ice will register as a shadow."

"Printout?" Tolland looked surprised. "You can print out here?"

Norah pointed to a cable from the GPR leading to a device still protected under the canopy. "No choice but to print. Computer screens use too much valuable battery power, so field glaciologists print data to heat-transfer printers. Colors aren't brilliant, but laser toner clumps below neg twenty. Learned that the hard way in Alaska."

Norah asked everyone to stand on the downhill side of the GPR as she prepared to align the transmitter such that it would scan the area of the meteorite hole, almost three football fields away.