Mayan underworld proves researchers' dream

The ancient Maya once believed that Mexico's jungle sinkholes containing crystalline waters were the gateway to the underworld and the lair of a surly rain god who had to be appeased with human sacrifices.Now, the "cenotes," deepsinkholes in limestone that have pools at the bottom, are yielding scientific discoveries including possible life-saving cancer treatments. Divers are dipping into the cenotes, which stud the Yucatan peninsula, to explore a vast underground river system.Hefting air tanks, guidelines and waterproof lamps, they have so far mapped 405 miles of channels that form part of a huge subterranean river delta flowing into the Caribbean sea, and they are only just starting. Scientists investigating the network of caverns and galleries, formed by rainwater passing through porous limestone, have found a wealth of early archeological relics and prehistoric animal bones. They also have identified dozens of new aquatic species specially adapted to extreme environmental conditions which could have medicalapplications. In the Riviera Maya, a strip of Caribbean tourist resorts including the world-famous archeological site of Tulum, there are more than 500 cenotes.

Some are open to the jungle, while others have tiny eye-like holes letting in sunlight and jungle roots. Their waters have filtered through sponge-like limestone which leaves them so transparent that divers say they feel like they are floating in space. The pools range in depth from a few feet (a meter) to an abyss where explorers have still not touched bottom at over 500 feet. "It is proving to be a totally unique environment," said marine biologist Tom Iliffe of Texas A&M University. "We are finding things down there including forms of life that no one had ever guessed existed, and there is a lot more work to be done."

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