Nordhausen hustled up behind him and was pleased to see the yawning portal ahead of them, wreathed in shadow. “Come on then,” he said, urging Paul on. “Are you worried about bears, or bandits? We’d be lucky to find anything else alive out here for miles—aside from those bastards on the camels. I wonder who they were?”
“Probably a small touring party.”
“But that fellow I was playing to—you know, the one with the pith helmet on. He looked European.”
“Some whacky college professor on sabbatical—or out to raid the nearest archeological dig site and make off with national antiquities perhaps?” Paul flashed a smile at his companion to let him know he would not labor the issue.
“This looks like a good spot to camp for the night,” said Nordhausen.
They were inside the mouth of the cave now, a leaf shaped feature scored into the rock that climbed some fifty feet over head. The professor leaned back, staring up at the cathedral of beautifully shaped stone. Colors of amber and rusty rose swirled along the contours of the cave walls to meet in a hard line, high above them. The ground was still sandy in places, with small rocks scattered on the floor of the cave.
As the professor began to clear an area to settle in, Paul took a moment to wander about the cave, working his way deeper into the fissure until he was lost in shadow. A moment later his voice echoed in the still chamber, resonant with a hint of urgency. “Nordhausen! Come here. I’ve found something!”
The professor gave a disconsolate sigh. “What? My, God, Paul. Let’s get some food going. Get over here and stop fooling around, will you?”
“No. You’ve got to see this. It’s weird!”
Robert shook his head, but he knew his friend well enough. He would have to humor him if he wanted to get a campfire going any time soon. “All right,” he said. “But what are we eating?”
He worked his way to the back of the cave, edging around a few large rocks thrusting up from the ground. He was hungry, and tired, and in no mood for Paul’s whimsical discoveries. Oddly, there was a passage at the back of the cave that sloped down at a steep angle.
“Paul?” The professor squinted in the deepening gloom. “Where are you?”
“Down here! Come on, it’s not far. Just keep following the passage, and keep to the right.”
Nordhausen pressed on, grumbling to himself as he went and feeling his way along the smooth rock as the darkness surrounded him. It was very cool. At least he could take some comfort from that. Soon he caught a glimmer of light, and realized that Paul had a small flashlight with him up ahead. He hurried on.
“Now what in the hell are you talking about—“ he stopped short when he saw what Paul was pointing at. There was a wide pool of water ahead, shimmering with a curious green hue in the light of Paul’s flashlight. “What did I tell you!” Nordhausen was exonerated. “All the water we need. It should be nice and cool! Just what I was hoping for. Probably one of those Nabatean water caches I was talking about.”
“Guess again,” said Paul. “It’s quite warm—almost hot. There must be a hot spring under this area. The ambient air temperature couldn’t produce this heat.”
Nordhausen was at his side at last, stooping to test the temperature with his hand. “Ouch! Why didn’t you warn me?”
“You would have tested it for yourself anyway,” Paul smiled. “But the temperature is not the only odd thing. Look at this!” Paul flicked off his flashlight and the darkness surrounded them. A moment later Nordhausen was amazed to see the entire pool of water glowing softly with an eerie green luminescence.
“Very strange,” he whispered. “ Is there something in the rock here?”
“No, I think it’s bio-luminescence,” said Paul.
“Bio-luminescence? I thought that was found mainly in the deep oceans.”
“It is. But they’ve isolated some weird bacteria in surface water that has this sort of glow about it. I read some papers on this last year, in fact. There’s more.” Paul flicked on his flashlight again and leaned toward Nordhausen. He was showing him a thin medallion that he wore on a chain about his neck, and even in the yellow cone of light it, too, had a strange green glow.
“What’s that?”
“It’s a radiation dosimeter from the lab,” said Paul. “I must have forgotten to take it off before I left the hotel in Amman. Oh, don’t worry, the green indicates safe levels—not much more than you get from direct sunlight. But there is no sunlight here. So, what’s causing this?”
“Are you suggesting the water is radioactive?”
Paul flicked off the flashlight and the chamber was effused with the milky green glow again. “Something’s going on here,” he said. “I wonder if this is an Oklo reaction?”
“What the devil is an Oklo reaction?”
“It’s that paper I was telling you about. The French discovered it at a mine in Gabon, Africa. They were mining uranium at Oklo and shipping the stuff off to France when they found that one of the shipments was very depleted.”
“Depleted?”
“Yes. It had a very low concentration of the fissionable isotope U-235, and it caused quite a scare at the time. They thought someone had managed to extract the isotope illegally.”
“Extract it? From raw ore? That’s highly unlikely. They probably just got a bad shipment.”
“Not exactly,” said Paul, and Nordhausen sensed that he was about to get a physics lecture. “You see, the concentration in natural ore is always at a constant level of 0.72 percent. Nature is very cooperative in that, and it’s actually one of the key tests the Atomic Energy Security guys make on all shipments. Variation in that isotope is a safe watch principle to detect tampering.”
“So what did they find out?”
“Well, they sent a big inspection team to Gabon and scoured the Oklo site pretty good. They were convinced that something was afoot but, to their surprise, they found an odd natural process at work.”
“Natural process?”
“Yes. Uranium is soluble in water in the presence of oxygen, and they found a nice underground stream at Oklo, deep in the mine.”
“So the isotope was leeched out by the water?” Nordhausen was trying to leap ahead to the right stone as he followed Paul across the stream of his thought.
“No, it doesn’t work that way. Oh, you might get a few uranyl ions in the water, but nothing like what they found. In order to deplete the ore sample to the degree it was degraded the U-235 actually had to be consumed in some way—in a reaction!”
“How is that possible in a stream bed?” Nordhausen was not seeing the opposite shore yet.
“Bacteria!” Paul sprung the answer on him. “Some sort of algal microorganism in the water was finding a way to concentrate the uranium that did leech out of the rocks and, by God, they did their job so well that a reaction started.”
“What are you talking about? Don’t you need a reactor chamber and fuel rods and all kinds of power for that?”
“The fuel was there in the U-235, and the reactor chamber, or chambers to be more precise, were the bacteria! They concentrated the stuff and, when you get to a certain critical mass in any one place, a reaction starts—on a very low level, mind you, but very well controlled. In fact, they theorize that it might have been sustained for over a million years! Imagine that—a natural nuclear reactor providing sustained power. They measured the estimated electrical output at many kilowatts, sighed with relief that no terrorism was involved, and called the whole thing an Oklo reaction.”
“And you think this is a pool of radioactive algae?”