could have been burned in the Middle Ages or last weekend, right?"
Tolland chuckled. "Nobody said science had all the answers."
Rachel let her mind wander aloud. "A fusion crust is essentially just a severe burn. Technically speaking, the burn on this rock could have happened at any time in the past half century, in any number of different ways."
"Wrong," Corky said. "Burned in any number of different ways? No. Burned in one way. Falling through the atmosphere."
"There's no other possibility? How about in a furnace?"
"A furnace?" Corky said. "These samples were examined under an electron microscope. Even the cleanest furnace on earth would have left fuel residue all over the stone-nuclear, chemical, fossil fuel. Forget it. And how about the striations from streaking through the atmosphere? You wouldn't get those in a furnace."
Rachel had forgotten about the orientation striations on the meteorite. It did indeed appear to have fallen through the air. "How about a volcano?" she ventured. "Ejecta thrown violently from an eruption?"
Corky shook his head. "The burn is far too clean."
Rachel glanced at Tolland.
The oceanographer nodded. "Sorry, I've had some experience with volcanoes, both above and below water. Corky's right. Volcanic ejecta is penetrated by dozens of toxins-carbon dioxide, sulfur dioxide, hydrogen sulfide, hydrochloric acid-all of which would have been detected in our electronic scans. That fusion crust, whether we like it or not, is the result of a clean atmospheric friction burn."
Rachel sighed, looking back out the window. A clean burn. The phrase stuck with her. She turned back to Tolland. "What do you mean by a clean burn?"
He shrugged. "Simply that under an electron microscope, we see no remnants of fuel elements, so we know heating was caused by kinetic energy and friction, rather than chemical or nuclear ingredients."
"If you didn't find any foreign fuel elements, what did you find? Specifically, what was the composition of the fusion crust?"
"We found," Corky said, "exactly what we expected to find. Pure atmospheric elements. Nitrogen, oxygen, hydrogen. No petroleums. No sulfurs. No volcanic acids. Nothing peculiar. All the stuff we see when meteorites fall through the atmosphere."
Rachel leaned back in her seat, her thoughts focusing now.
Corky leaned forward to look at her. "Please don't tell me your new theory is that NASA took a fossilized rock up in the space shuttle and sent it hurtling toward earth hoping nobody would notice the fireball, the massive crater, or the explosion?"
Rachel had not thought of that, although it was an interesting premise. Not feasible, but interesting all the same. Her thoughts were actually closer to home. All natural atmospheric elements. Clean burn. Striations from racing through the air. A faint light had gone off in a distant corner of her mind. "The ratios of the atmospheric elements you saw," she said. "Were they exactly the same ratios you see on every other meteorite with a fusion crust?"
Corky seemed to hedge slightly at the question. "Why do you ask?"
Rachel saw him hesitate and felt her pulse quicken. "The ratios were off, weren't they?"
"There is a scientific explanation."
Rachel's heart was suddenly pounding. "Did you by any chance see an unusually high content of one element in particular?"
Tolland and Corky exchanged startled looks. "Yes," Corky said, "but-"
"Was it ionized hydrogen?"
The astrophysicist's eyes turned to saucers. "How could you possibly know that!"
Tolland also looked utterly amazed.
Rachel stared at them both. "Why didn't anyone mention this to me?"
"Because there's a perfectly sound scientific explanation!" Corky declared.
"I'm all ears," Rachel said.
"There was surplus ionized hydrogen," Corky said, "because the meteorite passed through the atmosphere near the North Pole, where the earth's magnetic field causes an abnormally high concentration of hydrogen ions."
Rachel frowned. "Unfortunately, I have another explanation."
87
The fourth floor of NASA headquarters was less impressive than the lobby-long sterile corridors with office doors equally spaced along the walls. The corridor was deserted. Laminated signs pointed in all directions.
LANDSAT 7
TERRA
ACRIMSAT
JASON 1
AQUA
PODS
Gabrielle followed the signs for PODS. Winding her way down a series of long corridors and intersections, she came to a set of heavy steel doors. The stencil read:
Polar Orbiting Density Scanner (PODS)
Section Manager, Chris Harper
The doors were locked, secured both by key card and a PIN pad access. Gabrielle put her ear to the cold metal door. For a moment, she thought she heard talking. Arguing. Maybe not. She wondered if she should just bang on the door until someone inside let her in. Unfortunately, her plan for dealing with Chris Harper required a bit more subtlety than banging on doors. She looked around for another entrance but