In this photo from El Zacaton cenote, provided by Carnegie Mellon, research team members release the DEPTHX robot to begin its independent underwater exploration. Click photo for larger image.

How technologically convenient: Just put the robot resembling a giant tangerine into the world's largest sinkhole, then rev its engines and wait for it to complete the scientific exploration.

In late May, the robot did precisely that.

It resurfaced after hours of exploration with a mother lode of scientific data that included depth measurements, samples of gooey biofilm and the first-ever maps of El Zacaton cenote in Mexico. Data collected will keep scientists busy for months.

The success of the submarine robot, known as the Deep Phreatic Thermal Explorer, or DEPTHX, represents an important step in development of robots to explore ice-covered lakes in Antarctica and, eventually, lakes beneath the ice-encrusted surface of Europa, a moon of Jupiter.

Carnegie Mellon University's Robotics Institute developed DEPTHX's mapping and navigational systems.

David Wettergreen, associate research professor at CMU who headed the university's research team, said DEPTHX operated well without human assistance during several recent dives to the bottom of El Zacaton, the world's largest sinkhole or "cenote" in Mexico.

The robot determined that El Zacaton is more than 318 meters at its deepest, or about 1,043 feet. It also mapped the sinkhole, took water samples along with biological samples from its walls, Dr. Wettergreen said.

DEPTHX is 2.5 meters in diameter and includes 56 sonars that the CMU team used to determine the location of the vehicle as it explored the cenote for eight hours at a stretch and created maps of the sinkhole's interior.

Months ago, DEPTHX explored the depths of La Pilita Cenote, which proved to be 105 meters deep. During the May expedition, DEPTHX explored the depths of El Zacaton, Caracol and Poza Verda cenotes.

Each time, DEPTHX did the exploration autonomously and returned safely to the surface. Dr. Wettergreen said researchers monitored its progress only with a wristwatch, simply waiting for it to resurface.

"The vehicle operates in environments unknown to it before it enters them," he said.

In the project funded by NASA, Stone Aerospace Inc. of Austin, Texas, created DEPTHX, and recruited Dr. Wettergreen and a team of scientists from the universities of Arizona, Texas and Colorado to develop the robot.

CMU's crew included graduate student Nathaniel Fairfield, undergraduate David Stone, senior research programmer Dominic Jonak and project scientists George Kantor and Peter Coppin.

The expeditions proved that DEPTHX can operate in almost featureless environments, or ones where no major geological characteristic exists to serve as anchor points for its sensor system.

"It's exciting that we were able to map all cenotes in the region with early indications of interesting scientific results," Dr. Wettergreen said. "For example, the DNA sampling reveals six bacteria never found before."

Dr. Wettergreen also is working on a project to build a lunar rover for use in the proposed Shackleton Crater Expedition to investigate possible commercial opportunities at the Moon's South Pole.

That rover, scheduled for completion in September for NASA, would be used to drill meter-deep holes in craters to determine the availability of hydrogen for fuel.

In December 2008, Dr. Wettergreen and crew are scheduled to complete a robot similar to DEPTHX to explore underneath the ice of West Lake Bonney in Antarctica's Taylor Valley.

Exploration of that Antarctic lake sealed under kilometers of ice will serve as precursor to development of robots to explore Europa decades from now.