Phreatic is a word that refers to underground water, specifically to soil or rock below the water level in which all the spaces contain water.

The DEPTHX project is part of NASA’s Astrobiology Science and Technology for Exploring Planets (ASTEP) program. Its prime directive is to research and develop science and technology for the determination as to whether life exists or has existed outside of the Earth.

Stone Aerospace (Austin, Texas) built the underwater DEPTHX robot. This month’s exploration of Zacaton, Verde, and Caracol—three massive water-filled Mexican geothermal sinkholes and caves—from May 11 to 29, 2007, is the third dive for the autonomous undersea craft. The region of exploration is called Sistema Zacaton, which is located in central Mexico.

It is unknown the depth of Zacaton but DEPTHX team members are estimating it to be more than 1,000 meters (over one-half a mile) below the surface.

Pictures of the prep-work for the Zacaton mission are shown at: http://www.geo.utexas.edu/zacaton/depthx/Mission3-Blogs/2007_05_12/May12.htm.

The mission of the DEPTHX is to look for microbial life within these deep caves. It will perform this task with 36 onboard computers, 56 sonar sensors, and a series of guidance, depth, and velocity sensors.

Its primary exploratory instrument is the Simultaneous Localization and Mapping (SLAM) system, which is a guidance and navigation system that gives DEPTHX the ability to take sonar and other sensor readings to construct detailed three-dimensional maps of the areas it explores.

DEPTHX also carries a probe-like appendage that is capable of capturing solid and liquid samples.

The collaborators for DEPTHX include The University of Texas at Austin, Carnegie Mellon University, Colorado School of Mines, Southwest Research Institute, Universidad de Nuevo Leon, Facultad de Ciencias de la Tierra, and Universidat del Noreste.

Information about DEPTHX is contained at the University of Texas website: http://www.geo.utexas.edu/zacaton/depthx/; and the Field Robotics Center at Carnegie Mellon University (Robotics Institute) website: http://www.frc.ri.cmu.edu/project/depthx/.

Additional information about DEPTHX can be found at the NASA website: http://astrobiology.arc.nasa.gov/news/expandnews.cfm?id=10603.

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