Mexican Sinkhole May Lead NASA to Jupiter

Most important, it does its own thinking. As it swims down the limestone cave, which is 367 feet wide and at least 1,000 feet deep, the vehicle will probe the most interesting areas -- namely places where temperature, oxygen levels or other characteristics change, suggesting something is happening biologically, said Marcus Gary of the University of Texas, one of the lead scientists. Using a long arm with a pinkie-size knob, Depthx can grab samples from those spots.

At the end of each day, the vehicle must navigate back to the surface in much the same way a person lost in the woods searches for a route out -- except that Clementine has no map or trail. It creates its own.

Using supercomputers built by scientists at Carnegie Mellon University, the robot works off 500 three-dimensional maps that it is constantly sketching, said robotics professor David Wettergreen. Each new tidbit of information -- a rock jutting out, a narrow tunnel -- is fed into the computers, and the maps are updated in real time. The process is called simultaneous localization and mapping, or SLAM.

Like most humans, Clementine has gotten lost, prompting what Spear described as "freak time." On a practice dive in March in La Pilita, the second-deepest sinkhole in the collection of cenotes known as the Zacatón system, the robot did not resurface.

"I was awakened at 1:30 in the morning," said Gary, who was a commercial diver before he became a hydrogeologist. "I threw on my scuba tank and luckily found it wedged under some rocks."

As it turned out, the team had sent the robot down without all 56 sensors operating. It was a lesson worth the heart palpitations.

"The goal, from a technical point of view, is not to achieve perfect success," said Wettergreen. The scientists want to know "how it responds to failures."

Although NASA's long-term goal is to build a smaller robot that can function independently in outer space, the project is generating important earthly discoveries. With Clementine, scientists for the first time can examine specimens from the undisturbed netherworld of the sinkholes.

Diver Jim Bowden set a depth record of 925 feet in El Zacatón in 1994, but he never reached the bottom and his partner never returned. "This really is an example of exploration in a completely unknown, undeveloped environment," Wettergreen said.

"Everything we're finding there is unique and bizarre," Gary said. In preliminary sampling, the team has collected dozens of "previously undescribed" bacteria. Those new types of bacteria could conceivably lead to medical therapies, new plastics, stronger dental materials or better manufacturing processes.

Understanding the chemistry of the cenote -- how it formed and changed over thousands of years -- should help researchers locate and protect future water supplies, Spear said. Smaller versions of the robot, meanwhile, might be used to examine underwater dams or drilling platforms, he said.

Soon after the Mexico dive, Doran will begin preparing Clementine for the more challenging conditions of Antarctica. For the past 20 years, Doran's exploration of Lake Bonney has been severely limited. It often takes days for scientists to drill a few holes through the ice, which is about 15 feet thick, and then retrieve water samples from the narrow opening with a manual device. The robot will not have those limitations.

The Lake Bonney project, known as Endurance, "will probably take Depthx to its limits," Rummel said. After that, he is hoping for a smaller, tougher Clementine -- to send to Antarctica's Lake Vostok, where the ice layer above is even thicker -- 2.5 miles.