What would you need to explore an ocean on Europa, one of Jupiter's moons? It's hundreds of millions of miles away, and the ocean lies under a sheet of ice at least 10 kilometers (6 miles) thick. You'd probably need a spacecraft to land on the ice, a way to drill through the ice, and a submersible vehicle to explore the ocean and relate findings back to Earth.

This submersible vehicle is a project occupying the efforts of Dr. Bill Stone, CEO of Stone Aerospace in Austin, Texas. Stone and his colleagues have developed a prototype autonomous underwater vehicle (AUV) called Deep Phreatic Thermal Explorer (DEPTHX) for remote exploration and are currently testing it in a large underwater cave. In this article, we will examine this revolutionary AUV, its mission and how it fits into the larger scheme of extraterrestrial exploration.

the DEPTHX AUV
Photo © Stone Aerospace/PSC, Inc.
The DEPTHX autonomous underwater vehicle

The DEPTHX project is one of a series funded by NASA to develop robotic probes capable of exploring Europa (we will discuss why Europa is such an interesting target later). Stone Aerospace designed, built and operates DEPTHX in cooperation with its partners:

DEPTHX on deck during one of its tests
Photo © Stone Aerospace/PSC, Inc.
DEPTHX on deck during one if its tests

The DEPTHX project is designed to answer these questions:

  1. Can a fully-automated AUV explore an unknown, three-dimensional world on a day-to-day basis unaided by mission control? In doing so, can it create and use maps to navigate and return to a "home location" to report its findings?
  2. Can the robot be programmed to detect signs of microbial life as well as collect and analyze samples?

DEPTH X has completed tank testing (which includes systems integration and mapping) and is now preparing to undergo tests in a completely unknown environment: Mexico's Zacatón cenote. 

Next, let's take a closer look at the AUV and its systems.

Cenotes
Cenotes (pronounced "say-NO-tay") are large freshwater sinkholes found in Mexico's Yucután Peninsula. These cenotes formed when underground water etched into the porous limestone bedrock that makes up the entire peninsula.  The cenote in Zacáton is one of five connected cenotes and is thought to be the deepest in the world. Zacáton also has a  hydrothermal spring inside it.