An Alert Unlike Any Other

"You'd think it would be easier to communicate with humans" than extraterrestrials, he said. "But the [Pioneer] spacecraft will never land, so it's only going to be found by some highly developed technological culture. All we can guess about the future inhabitants of the area near WIPP is that they are human -- unless they are cyborgs.... Once you have people with augmented brains or genetically engineered minds with enhanced perceptions, you can't be sure how human they will be."

There are at least two universally understood pictographic forms. The human stick figure has survived nearly unchanged from Stone Age cave drawings to the doors of modern public restrooms. And the sequential panel, or comic strip, was developed independently by ancient Egyptians, American Indians and medieval Japanese.

They also are far from foolproof. The South Africa Chamber of Mines learned this when it used a simple picture sequence to train illiterate miners to clear rocks from mine tracks. Instead of improving, the rock problem worsened.

"Miners were indeed reading the message, but from right to left," said Lomberg, a former WIPP advisor. "They obligingly dumped their rocks on the tracks."

Nelson considers such concerns far-fetched, citing 30,000-year-old cave drawings.

"I understand those cave drawings and I don't speak Neanderthal.... He's killing a bison, 'bison -- food!' I can do pictographs just as well," he said. "I can convey an absolute sense of danger."

Yet the same Stone Age caves contain markings and handprints whose meaning remains obscure.

"The scribbles, we have no idea what they are.... The handprints -- is that the artist's signature?" Lomberg said. "We don't know. Of course the big difference is that these were not intended as messages to the future -- so far as we can tell."

With so many ways to fail, WIPP's planners opted for the classic American approach: Think big and leave no stone unturned. The plan will take more than a century to implement.

To grasp the scale of the warnings, start with the Great Pyramid in Egypt, built from more than 6.5 million tons of stone covering 13 acres. Multiply that mass by five, and you have the first warning layer: a 98-foot-wide, 33-foot-tall, 2-mile-long berm surrounding the site. That's just to get the attention of anyone who happens by.

"Size equates with importance. The bigger the animal the more that animal is to be reckoned with," Givens said.