Footfall

She turned left at the intersection, and the way became even steeper. The TR-7 labored through the climb. There were fewer fresh lava fields here; now they were on the side of Mauna Kea . “She” was supposed to be pretty thoroughly dormant. They drove through endless miles of ranchlands given by King Kamehameha to a British sailor who’d become the king’s friend.

Richard Owen woke just as they reached the “temporary” wooden astronomy base station. “We stop here,” he said. “Have some lunch.”

There wasn’t much there. Long one-story wooden barracks in a sea of lava and mud, with a few straggly trees trying to live in the lava field. She pulled in alongside several GMC Jimmy fourwheel-drive vehicles. “We could go on up,” she said. “I don’t really need lunch.”

“Regulations. Acclimatization. It’s nearly fourteen thousand feet at the top. Pretty thin air. Thin enough here at ten thousand It’s not easy to do anything, even walk, until you get used to it.”

By the time they reached the clapboard barracks buildings she was ready to agree.

There were half a dozen observatories on the lip of the volcano. Richard parked the Jimmy in front of the NASA building. It looked like an observatory in a Bugs Bunny cartoon: a square concrete building under a shiny metal dome.

“Do I get to look through the telescope?” she asked.

He didn’t laugh. Maybe he had answered that one too often. “No one looks through telescopes anymore. We just take pictures.” He led the way inside, through bare-walled corridors and down an iron stairway to a lounge furnished with chrome-steel office tables and chairs.

There was a woman in the lounge. She was about Jeanette’s age, and she would have been pretty if she’d washed her face and put on some lipstick. She was frowning heavily as she drank coffee.

“Mary Alice,” Owen said, “this is Jeanette Crichton. Captain Crichton, Army Intelligence. Not a spook, she does photo reconnaissance and that sort of thing. Dr. Mary Alice Mouton. She’s an asteroid specialist.”

“Hi,” Mary Alice said. She went on frowning.

“Problem?” Owen asked.

“Sort of.” She didn’t seem to notice Jeanette at all. “Rick, I wish you’d come look at this.”

“Sure.”

Dr. Mouton led the way and Rick Owen followed. Jeanette shook her head and tagged after them, through another corridor and up some stairs, past an untidy computer room. All mad, she thought. But what did I expect?

She hadn’t known what to expect at all. This was her first trip to Hawaii , courtesy of an engineering association meeting that invited her to speak on satellite observation. That conference was over and she was taking a couple of days leave, swimming the Big Island’s reefs and enjoying the sun. She didn’t know anyone in Hawaii , and it had been pretty dull. Jeanette began to make plans to visit Linda and Edmund before going back to Fort Bragg .

Then Richard Owen had met her at the reef. They’d had breakfast after their swim, and he’d invited her to come up to see the observatory. She’d brought a sleeping bag; she didn’t know whether Owen expected to share it with her, but from little things he’d said at lunch and on the drive up after lunch she was pretty sure he’d make the offer. She’d been trying to decide what to do when he did.

Now it was as if she weren’t there at all.

She followed them into a small, cluttered room. There was a big viewscreen in one corner. Dr. Mouton did things to the controls and a field of stars showed on the screen. She did something else, and the star field blinked on and off; as it did, one star seemed to jump back and forth.

“New asteroid?” Owen asked.

“That’s what I thought,” Dr. Mouton said. “Except … take a good look, Rick. And think about what you’re seeing.”

He stared at the screen. Jeanette came closer. She couldn’t see anything strange. You take the pictures on two different nights and do a blink comparison. The regular stars won’t have moved enough to notice, but anything that moves against the background of the “fixed stars,” like a planet or an asteroid, will be in two different places on the two different photos. Blink back and forth between the two plates: the “moving” body would seem to jump back and forth. That was how Clyde Tombaugh discovered Pluto. It was also a standard photo reconnaissance technique, to see what had changed in the interval between two satellite photos.

“What’s the problem?” Owen asked.

“That’s moving too far for the interval.”

“It’s close …”

“Not that close,” she said. “I got the plates from a few weeks ago. Rick, I had to trace back damn near night by night, it’s moving so fast! It’s in a hyperbolic orbit.”

“Come on, it can’t be!”

“It is,” Dr. Mouton said.

“Excuse me,” Jeanette said. They both turned to look at her. They’d obviously forgotten she was there. “What’s a hyperbolic orbit?”

“Fast,” Owen said. “Moving too fast for the sun’s gravity. Objects in a hyperbolic orbit can escape from the solar system altogether.”

She frowned. “How could something be moving that fast?”