* Astronomy

The Maya called them dzonots (sacred wells). The Spanish mangling the Mayan name called them cenotes. We call them unsurpassable swimming holes.
The Yucatán peninsula, where most of Mexico's cenotes are found, is a geological oddity: a flat limestone slab too porous to hold water on the surface. Rainwater seeps through the stone and carves subterranean channels in the peninsula's foundation. When sinkholes create breaches in the tunnel ceilings, subterranean waters are revealed to the world above.
Divers began surveying these wells and caves in the 1980s, bestowing names that range from the grandiose (Tajmajal) to the whimsical (Carwash, describing its popular use in past years). Thousands of cenotes have been discovered in the Caribbean coastal state of Quintana Roo alone, many linked to the world's three longest underground cave systems. Countless others remain hidden by jungle. Unearthed bones, precious stones and ancient ceramics suggest the ancient Maya used cenotes, regarded as gateways to the underworld, as ceremonial sites.



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NASAs robotic submarine, DEPTHX has mapped the bottom of the worlds deepest sinkhole, or cenote, the El Zacatón.
Entering El Zacatón for the first time this Wednesday, DEPTHX dived down to 270 metres, creating the first map of the giant cavity, which is large enough to swallow New York's Chrysler Building.
The maps showed that the sinkhole has a sloped bottom, about 290 metres at shallowest, which extends down to over 300 metres.
Researchers said this meant that the two drivers, Sheck Exley and Jim Bowden, who made a record-breaking scuba dive in 1994 in search of the bottom, were just a few metres off the sloping floor. Bowden set a new scuba depth record of 281.94 metres, while Exley died at a depth just a few metres shallower.
Scientists further said the sinkhole could be connected to even deeper caverns, adding that at the bottom of the slope was an area DEPTHX could not probe.

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It may not show up on MapQuest, but NASA scientists are betting that the best route to Jupiter and its ice-crusted moon Europa runs through an underwater cavern in Mexico.
Though the space mission is probably 30 years off, the trek begins in earnest today outside the city of Tampico. A 60-ton crane is scheduled to lower a giant orange robot dubbed "Clementine" into what is believed to be the deepest flooded sinkhole in the world.
For the next two weeks, the fully autonomous robot, which bears an uncanny resemblance to a Volkswagen Beetle, will plumb the previously inaccessible microbial mysteries of the sinkhole -- or "cenote" -- El Zacatón.

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