DepthX - Autonomous Underwater Robotics
Robotics & Automation Engineering

image of 3-D Model of DepthX

3-D Model of DepthX

 
image of DEPTHX (detailed 3-D model).

Click image for enlarged view 
DEPTHX (detailed 3-D model).

 
image of Camera view of microbial life

Camera view of microbial life

DepthX (DEep Phreatic THermal eXplorer) is a NASA Astrobiology Science and Technology for Exploring Planets (ASTEP) project to design, develop, and field-test a robotic vehicle to explore extreme aqueous environments. The principal astrobiological science objective of DepthX is to develop an advanced methodology and protocol for the discrimination of microbial life in a sub-aqueous environment. The methodology and protocol might be used in exploration and search for life in locations such as Europa, the sixth moon of Jupiter. This exploration required the design, development, and demonstration of a fully autonomous architecture for intelligent biological sample detection and collection. Southwest Research Institute (SwRI) designed, assembled, and tested the science package capable of performing the following functions:

  • Acquiring data from a hierarchical suite of on-board microbial life detection sensors and processors and analyzing the data to determine whether life is present
  • Aseptically collecting samples and returning them for ex-situ laboratory analysis
  • Autonomously searching for life and returning samples. This capability will be tested in El Zacatón, an unexplored, water-filled sinkhole in Mexico.

Background of DepthX

Recent observations show oceans of liquid water and a source of energy — the two essential requirements for life — under an ice layer on Europa. This is certainly a place worthy of investigating, but this investigation will be a difficult and challenging task involving robotic explorers and robotic scientists. Reaching liquid water will involve not just landing on the target but penetrating several kilometers (at least) of ice. After drilling or melting through the ice layer, an explorer may find water-filled caves with interconnecting rooms, dead-end passageways, overhanging ice shelves, and other hazards. The explorer must be able to navigate through these hazards and construct a map for the return. The robot scientist must locate regions where life forms are likely to be found and then search, identify, and characterize living organisms.

Before attempting such exploration, the NASA program, ASTEP, is intended to develop the capabilities necessary for future space missions and conduct tests on Earth. DepthX, one of the ASTEP projects, is an initial step in this direction. DepthX developed the combined capabilities of a robot explorer and a robot scientist. These capabilities were implemented in an autonomous submersible vehicle and tested in El Zacatón, one of the world's largest water-filled sinkholes. Zacatón, located near Tampico, Mexico, is unexplored but is known to be more than 350 meters deep.

DepthX as Solution

SwRI implemented the robot science component of DepthX responsible for locating and identifying life forms. The robot science package is intended to roughly follow the approach of a field biologist, first looking for locations of interest and then making a closer examination before deciding when to collect samples. The DepthX science package includes environmental sensors, cameras, a microscope, an extensible probe arm, means for collecting both solid and liquid samples, and a dedicated computer for analyzing data and controlling the sample collection subsystems.

As the vehicle explores, the science computer analyzes sensor data to identify locations with conditions where life forms are likely to be found. To accomplish this, SwRI designed a suite of instruments including:

  • Three cameras with onboard image analysis software
  • Camera view of microbial life
  • A custom telescoping probe arm
  • A coring system to collect samples from the cell walls
  • Flexible containers for collecting water samples
  • An on-board computer for image and data analysis as well as control of sample collection

The science computer communicates with the navigation/control computer as the robot vehicle explores the underwater cave. When the cameras or chemical sensors locate "interesting" conditions (thermal vents, sulfide concentrations, temperature gradients, etc.), the vehicle will stop exploring and switch to "robot scientist" mode. Additional observations will be made including image analysis of cave walls and microscopic examination of water samples using a high-pressure flow cell.

image of DepthX, a NASA Astrobiology Science and Technology for Exploring Planets project to design, develop, and field-test a robotic vehicle to explore extreme aqueous environments.

DepthX was a NASA Astrobiology Science and Technology for Exploring Planets project to design, develop, and field-test a robotic vehicle to explore extreme aqueous environments.

image of The SwRI-developed robotic arm carries a video camera, a tube for collecting water samples and a replaceable coring tube.

The SwRI-developed robotic arm carries a video camera, a tube for collecting water samples and a replaceable coring tube.

image of DepthX: Click image to enlarge

Click image for enlarged view 
DepthX


Science computer algorithms and heuristics identify living organisms and especially unique organisms that have not been observed before. Based on analysis results, a sample may be collected from the water or the cave wall, or the robot may switch back to explorer mode and search other locations. When the mission objectives are completed, the robot will return to the surface where the samples can be analyzed for confirmation.

image of sample operation

Sample operation. View the video.

 
image of DepthX successfully navigated 1,099 feet to the bottom of the Zacatón sinkhole

DepthX successfully navigated 1,099 feet to the bottom of the Zacatón sinkhole, collected water and solid samples, and returned to the surface. The samples are being analyzed, and scientists hope to discover entirely new strains of bacteria and algae. (Photo compliments of David Wettergreen/Carnegie Mellon University).

 
image of the SwRI-developed hydraulically operated robotic arm carrying a video camera

The SwRI-developed hydraulically operated robotic arm carries a video camera, a tool for collecting water samples, and a replaceable coring tube for collecting solid samples of algae mat or other growth on the sinkhole wall.

DepthX Results/Outcome

DepthX successfully navigated 1,099 feet to the bottom of the Zacatón sinkhole, collected water and solid samples, and returned to the surface. The samples are being analyzed, and scientists hope to discover entirely new strains of bacteria and algae. (Photo compliments of David Wettergreen/Carnegie Mellon University)

The SwRI-developed hydraulically operated robotic arm carries a video camera, a tool for collecting water samples, and a replaceable coring tube for collecting solid samples of algae mat or other growth on the sinkhole wall.

Field tests were conducted in several cenotes near Aldama, located in a karst limestone region about 75 miles northwest of Tampico, Mexico. In February 2007, a field base was set up on Rancho Azfruso, the location of five water-filled sinkholes or cenotes. During the first tests, conducted in cenote La Pilita, the collective DepthX functions including navigation algorithms, water chemistry sensors, imaging systems, and sample collection were evaluated. Several problems were identified including difficulty in detecting wall contact due to thick layers of algae mat on the wall surface and insufficient illumination for the underwater cameras. Modifications were made to correct these problems and a second series of tests was conducted in March of 2007. Robotic exploration and mapping of La Pilita found several previously undiscovered passageways and large rooms connected to the main pool. Liquid and solid samples were taken at several depths in the sinkhole and the solid sampler successfully captured cores of biological material (algae mat) on the surface as well as cores of limestone wall material.

After the March tests, additional modifications and improvements were made to the system and a final test was conducted in May 2007. This test was conducted at El Zucatón, one of the deepest sinkholes in the world, which had never been completely explored.

The robot explored the cave during several dives of up to four hours duration, reaching the bottom at 319 meters below the water surface. Mapping showed the cenote to be a near vertical cylinder of water, roughly 75 meters in diameters. Below the photic zone, water chemistry was very homogenous and wall images showed little change The solid sampler performed satisfactorily and both water and solid samples were collected at several locations and depths. Biological cultures and analysis of the sample material have yielded at least six new phyla of bacteria. The field tests successfully demonstrated the capability of the robotic system to autonomously navigate, map, and analyze the environment, select locations for sampling and return liquid and solid samples.

Partner Websites

SwRI DepthX Publications

Franke, E.A., M.J. Magee, M.P. Rigney, and W. Stone. Progress Toward the Development of Lifeform Detetection Algorithms for the Deep Phreatic Thermal eXplorer (DEPTHX). Proceedings of the International Society for Optical Engineering Conference on Instruments, Methods and Missions for Astrobiology IX, San Diego, California, July-August 2005.

Underwater probe to explore Earth and possibly Jupiter's moon

Related Terminology

automation  •  robotic aqueous vehicle  •  robotics design  •  robotic torque converter  •  DepthX  •  ASTEP  •  NASA  •   astrobiology  •  autonomous architecture  •  microbial life detection sensors



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07/13/16