2007-03-12 | SCIENCE
DEPTHX Robot Prepares to Explore Earths Deepest Sinkhole

By Henry Bortman

A group of scientists and engineers are in northeastern Mexico this month to test an autonomous underwater robot, DEPTHX. The goal of their project is to create a comprehensive 3-D map of the worlds deepest sinkhole, Cenote Zacatón, and to collect water samples to learn about its chemistry and biology. The current activity is a test run in a smaller, nearby sinkhole, in preparation for deploying DEPTHX in Zacatón.

Cenote Zacatón is located in the state of Tamaulipas close to the town of Aldama near the northeastern coast of Mexico.

Zacatón is a forbidding place. It has never been fully explored, and no one knows exactly how deep it is, but estimates are that its floor lies more than 1,000 feet below the surface. A pair of SCUBA divers attempted to plumb its depths in 1994. After descending to 898 feet, one of the divers, Jim Bowden, was forced to turn back. At 925 feet, the water pressure is nearly 30 times what it is at sea level. Bowdens partner, Sheck Exley, drowned in his attempt to reach the bottom.

DEPTHX is an autonomous robot capable of exploring and mapping underwater caverns. Bill Stone of Stone Aerospace in Austin, Texas, who heads the DEPTHX team, is hopeful that his robot can succeed where human divers could not. The Deep Phreatic Thermal Explorer (phreatic refers to underground water), which looks vaguely like Marvin the Martians Bubble Rocket, is equipped with 56 SONAR sensors and sophisticated software that enable it to navigate its way through a flooded underground cavern and produce an accurate three-dimensional map of its interior surfaces.

DEPTHX is not tethered in any way to the surface. It contains its own power and its own computer hardware and software. Other AUVs (autonomous underwater vehicles) have been used to map the ocean floor, but DEPTHX is the first with the sensitivity and maneuvering ability to make detailed maps of irregular confined spaces like Zacatón.

NASA funds the DEPTHX project through its ASTEP (Astrobiology Science and Technology for Exploring Planets) program. The DEPTHX project brings Stone Aerospace together with researchers and technical experts from Southwest Research Institute, Colorado School of Mines, University of Texas at Austin, University of Arizona and the Carnegie Mellon University.

Doctoral student Marcus Gary SCUBA dives with the DEPTHX probe during initial in-water tests at The University of Texas at Austin Applied Research Laboratories wet test facility Image credit: The University of Texas at Austin

NASA established the ASTEP program both to develop technologies that will be needed to search for life on other worlds, and to conduct scientific investigations of organisms that inhabit extreme environments on Earth. The lessons learned from building DEPTHX will help NASA design a future space probe for exploring Jupiters giant moon Europa. Beneath its thick frozen crust, Europa is thought to have a worldwide ocean, which some scientists believe is capable of supporting life.

A preliminary field test of DEPTHX was conducted successfully in February of this year at a smaller nearby sinkhole, La Pilita. The test currently underway, also at La Pilita, has been dubbed a "dress rehearsal" for the exploration of Zacaton, which will take place in May.

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