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DepthX - from Autonomous Underwater Robot Explorer*
Ernest Franke1, Michael Rigney1, William C. Stone2, and Marcus O. Gary3
Search and Discovery Article #40311 (2008)
Posted November 13, 2008
Adapted from oral presentation at AAPG Annual Convention, San Antonio, Texas, April 20-23, 2008
1Southwest Research Institute, San Antonio, TX ([email protected])
2Stone Aerospace/PSC Inc., Austin, TX
3The University of Texas, Austin, TX
The DEep Phreatic THermal eXplorer (DepthX) is an autonomous robot developed to investigate and test concepts for exploring liquid water oceans on Europa, the fifth moon of Jupiter. The oceans on Europa are covered by an ice layer several kilometers thick and may have channels or cracks that are much more difficult to explore than large open spaces. The DepthX project was funded by NASA to investigate techniques for a future mission to Europa. Although much of the NASA interest is directed toward the search for life, many of the techniques investigated have applications in exploration for other resources.
The DepthX robot is battery powered with multiple computers dedicated to various tasks. High resolution sonar and inertial sensors are used to map the environment and navigate in confined spaces while learning a safe return path. Water chemistry sensors measure temperature, pH, salinity, sulphide, and conductivity to identify locations where energy gradients may support life. When such a location is found, the robot can maneuver near the wall, capture images from two video cameras and use image analysis to identify significant visual patterns. A video microscope searches for microbial activity. The DepthX robot also includes a probe arm that can be extended to a wall and a solid sampler to capture core samples at locations identified by software algorithms for return and analysis.
Autonomous operation of the DepthX robot was tested at Sistema Zacatón, near Tampico, Mexico in May, 2007. The robot successfully explored cenote Zacatón to a depth of 1100 feet, mapping the cave walls and returning samples.
Goals and Steps for Test(s)
DepthX Goal - Develop Technology for Autonomous Search for Life
Goal 1 – Navigate Through Unexplored Underwater Regions, Generate Map, Return
Goal 2 – Identify Locations Likely to Support Life, Search for Life Forms, Collect Specimens and Return Them
Step 1 — Find Locations Suitable for Life, Sources of Energy
Step 2 — Conduct More Detailed Search at Promising Locations
Step 3 – Sample collection
Solid sample retrieval
Exploration and Mapping
· Hierarchical system architecture including decision-making applicable to other autonomous systems and robots.
· SLAM (Simultaneous Location and Mapping) using inertial navigation and sonar wall signatures.
Autonomous Science Capability.
· Methods for sensors, image analysis, and decision making applicable to other autonomous systems, robots.
· Systems and devices for collecting liquid and solid samples.
· Several new species of microbes discovered in Zacaton.
· Lake Bonney, Antarctica - Knowledge gained and some vehicle hardware will be used to explore and map an ice covered lake (Endurance).
· Europa –Autonomous underwater techniques will help explore and search for extraterrestrial life.
· Titan – Autonomous underwater capability may be used to explore liquid methane lakes on Titan (largest of Saturn’s moons).
Stevenson, D., 2000, Europa’s ocean – the case strengthens: Science, v. 289/5483, p. 1305-1307.