“Mercury poisoning this far from land?” Pitt asked. “Are you sure?”
“We’ve tested all but the last batch of seawater samples, and they all show highly toxic concentrations of methyl mercury. We’ve found bioaccumulation in the plankton, which then works itself up the food chain. We also sampled a number of dead fish, which seem to be present in large numbers, and confirmed the presence of mercury.”
“Mercury is nothing new,” Pitt said. “Industrial air pollution has been increasing mercury levels in the oceans for decades. But this is different?”
Bhatt nodded. “The concentration is exponentially higher. This isn’t just some general acid rain but a specific, localized incident. The only comparable toxicity I can find historically is from Minamata, Japan. A factory there dumped twenty-seven tons of methyl mercury into the bay over several decades, resulting in catastrophic damage to nearby residents and local sea life. Nearly two thousand deaths have been attributed to it.”
“But we’re fifty miles from land,” Giordino said.
“If I had to guess,” Bhatt said, “I would say that someone has been dumping industrial wastes out here.”
“If that’s the case,” Pitt said, “the AUV will show it.”
“The concentration was highest in the water sample where the AUV was launched,” Bhatt said.
“She’s due up any minute,” Giordino said. “Hopefully, the litterbugs left a calling card.”
The trio retreated to the stern deck as the AUV surfaced and was hoisted aboard. Giordino downloaded the sonar data onto a portable hard drive and returned to the lab to review the images. He quickly advanced through the AUV’s acoustic imagery, which showed hundred-meter swaths of the undulating seafloor. There were rocks, sand, and even occasional dunes, but no drums, crates, or other debris. Only an odd series of shadowy lines marred the bottom, concentrated in a slight underwater valley.
“Nothing obvious,” Giordino said, “though those lines might be worth a closer look. It’s difficult to say if they are geological features or man-made.”
“We might be dealing with something that’s buried,” Pitt said, “in which case we’ve got our work cut out for us.”
“I can reconfigure the AUV to perform a sub-bottom profile. That would give us a limited look beneath the seabed, if the sediment conditions are friendly.”
Pitt stared at the sonar screen, knowing the answer to the mystery was there somewhere. He shook his head slowly. “No, let’s move on. It looks to be a sandy bottom here, which isn’t conducive to the sub-bottom profiler. We’ve got two more dead zones to investigate, and I’ll wager the source will be evident at one of those.”
Without debate, Giordino relayed the order to the bridge, knowing from the past that Pitt’s intuition was as good as gold.
14
The battered green panel van turned off the dirt road and pulled to a stop on a high bluff. As a cloud of trailing dust settled, Dr. Torres climbed out of the driver’s seat and spread a topographic map across the hood. Dirk and Summer joined him as he took a black pen and marked an X through a square grid. A half-dozen adjacent grids were already marked.
“That was the last accessible area around the base of Lomo del Toro to survey,” Torres said in a tired voice. “Aside from the two abandoned mine shafts we crawled through, I’m afraid we’ve found nothing resembling a cave, or even a potentially buried one.”
“Dr. Madero told us it was a long shot,” Summer said.
“True. I wish he was here to see for himself.”
“He was disappointed, but he couldn’t get out of a speaking engagement in Mexico City,” Summer said. “We did promise him we’d give it our best effort.”
Torres nodded. He was certain they were in the right place. He and Madero had spent days studying the codex and comparing it to other Aztec documents, as well as reading contemporary Spanish accounts. Bit by bit, they deciphered additional clues that seemed to confirm the Aztecs had carried the half stone to Zimapán.
One notation indicated they had traveled north, presumably from their capital of Tenochtitlan. Another indicated they stopped at Tula along the w
ay. Tula was an ancient Toltec city near the northern fringe of the Aztec empire, just over twenty miles away. The codex revealed the warriors had traveled two days beyond Tula, traversing a steep ravine, before depositing the half stone in a cave near the base of a cow-shaped mountain. Everything pointed to Lomo del Toro.
But two days of searching the dry, rugged region in Mexico’s Central Plateau had led nowhere. After arriving at the mining town of Zimapán, the three drove through the narrow canyon of Barranca de Tolimán, which seemed to align with the Aztec description. At Lomo del Toro mountain, they initiated a search around its perimeter. Much was inaccessible by car, forcing them to hike the rugged terrain. They were now hot, dusty, and tired of dodging rattlesnakes.
They had explored all around the mountain, except for the El Monte Mine facility facing Zimapán, which encompassed the original Spanish digs. With most of its silver and lead deposits having been mined in excavations that stretched back to the sixteenth century, it was now a small operation. Torres conferred with mine officials and a local historian, but no one recalled any stories of an Aztec cave, or even an Aztec presence in the area. Fears that the stone was hidden in an early mine shaft were minimized when they realized the mining operation was high up the mountain.
Torres drank warm water from his canteen and shook his head. “My friends, perhaps the Aztec cow mountain is located elsewhere.”
Dirk produced a copy of the codex page that illustrated the burial site. He gazed from the mountain image to the imposing heights of Lomo del Toro. “The ridge highlines look like a match to me.”
Summer gazed at the mountain and agreed. Studying the photocopy, she noticed a faint line beneath the cave. “What’s that?”
Dirk and Torres peered at the line.