August 14, 2007 — Image analysis systems and a robotic arm developed by Southwest Research Institute (SwRI) engineers helped a NASA-funded, deep-diving robot seek out and collect biological samples from the bottom of one of the world's deepest water-filled sinkholes.
The Deep Phreatic Thermal Explorer (DEPTHX), an autonomous underwater robot, has more than 100 sensors and 36 onboard computers. It is fitted with video cameras and a robotic arm to collect biological samples. In May, DEPTHX descended 1,099 feet to the bottom of the Zacaton sinkhole north of Tampico, Mexico. The mission successfully tested technology that could be used to explore Europa, the fifth moon of Jupiter, which is believed to contain an ocean of liquid water beneath its icy crust.
Funded by NASA's Astrobiology Science and Technology for Exploring Planets program, the DEPTHX project is led by Stone Aerospace and includes participation by SwRI, Carnegie-Mellon University, The University of Texas at Austin, Colorado School of Mines and the University of Arizona.
Dr. Ernest Franke, SwRI project manager, said, "One of the major goals of the DEPTHX project is to demonstrate that the robot can explore and search for life completely autonomously. The distance and isolation of ice-covered oceans on Europa will require a robot that can operate independently, much like a human explorer."
To achieve this, SwRI engineers developed image analysis algorithms to identify patterns associated with living organisms in much the same way a field biologist recognizes algae mats in a pond as evidence of life.
"We pump a water sample into a flow cell and analyze a sequence of images to detect the motion and frequency of microorganisms," said Dr. Mike Rigney of SwRI's Automation and Data Systems Division. "Color images of the wall are analyzed to characterize the color and texture of wall surface regions. Analysis software compares these attributes to a model of what is 'normally' observed in the environment to identify interesting regions. A location with a high microbe concentration or unusual image attributes is where we want to obtain a sample."
SwRI engineers also developed a hydraulically operated robot arm that can reach six feet beyond the edge of the vehicle. The robot arm carries a video camera, a tube for collecting water samples and a unique coring tool for collecting solid samples of algae mat or other growth on the wall of the sinkhole. Water samples are collected in five different containers controlled by the science computer.
Driven by a single spring, the solid sample collecting tool drives a hollow coring tube about an inch into a surface. The tube automatically rotates, retracts and closes the tube to secure the sample.
SwRI engineering technologist Tom Lyons explained, "The spring drives the tube with such force that the complete operation takes less than half a second. We designed a replaceable coring tube since the impact is so great that the tube can be damaged if it is driven into a hard rock surface."
No human divers have reached the bottom of the Zacaton sinkhole, but DEPTHX successfully navigated 1,099 feet to the bottom, collected water and solid samples and returned to the surface. The samples are undergoing analysis, and scientists hope to discover entirely new strains of bacteria and algae.
Future tests of the DEPTHX navigation and autonomous operation methods will be done by NASA in conjunction with the National Science Foundation in Antarctica. There, an upgraded DEPTHX will study Lake Bonney, a permanently ice-covered lake that more closely resembles Europa than the warm waters of Zacaton.
For more information, contact Deb Schmid, +1 210 522 2254, Communications Department, Southwest Research Institute, PO Drawer 28510, San Antonio, TX 78228-0510.