If humans ever do establish a presence on Europa, it will surely be somewhere under the ice. Assuming, that is, that the ice isn’t too thick, and to learn about that we have to await further study, and probably a Galilean moon orbiter of some kind that can observe Europa up close and for lengthy periods. But assuming the ice is more than a few meters thick, it should provide radiation screening, and getting down into that presumed Europan ocean is where we want to be in the search for life.
Of course, the first undersea explorations on the Jovian moon will have to be robotic, and here we can talk about technologies under development today. NASA has funded a self-contained robot submarine called the Deep Phreatic Thermal Explorer (DEPTHX) that operates with an unusual degree of autonomy, navigating with an array of 56 sonar sensors and an inertial guidance system. Now a series of tests in Mexico at a geothermal sinkhole, or cenote, called La Pilita have tested out key components, proving DEPTHX can manage unexplored three-dimensional spaces.
Image: DEPTHX in the water at Cenote la Pilita. Credit: David Wettergreen/CMU.
What’s ahead for the technology is a much more challenging task: to explore the Zacatón sinkhole in the Mexican state of Tamaulipas in May. La Pilita seems easy by comparison. It’s about 100 meters deep, filled with overhanging rock and interesting biology. The depth of the Zacatón site is unknown. But Bill Stone (Stone Aerospace), leader of (DEPTHX) mission, sees La Pilita as a powerful proof of concept:
“The fact that it ran untethered in a complicated, unexplored three-dimensional space is very impressive. That’s a fundamentally new capability never before demonstrated in autonomous underwater vehicles (AUVs).”
Even so, don’t underestimate the challenge at Zacatón. From a Pittsburgh Tribune-Review story on the technology:
Divers have explored Zacaton for decades, but a turning point came on April 6, 1994, when cave-diving pioneers Jim Bowden and Sheck Exley strapped on scuba tanks and tried to reach Zacaton’s elusive bottom. Bowden made it to a depth of 925 feet — a world record for deep-water diving since broken — but tragedy overshadowed his feat. Exley did not return to the surface.
Using software called SLAM (Simultaneous Localization and Mapping) developed at CMU, DEPTHX maneuvered close to rocky walls at La Pilita and was able to take core samples. With Zacatón on the horizon, the robot’s ability to determine its position within 15 centimeters using sonar seems reassuring. Will technologies like this one day explore a Europan sea? Perhaps, but they’ll be just one part of a much larger challenge depending on how deeply we need to drill to reach liquid water.
And if any of this work on autonomous exploration technologies sounds familiar, it may be because DEPTHX’s software is being developed by CMU’s David Wettergreen, who was project leader for the four-wheeled Zoë robot recently tested in Chile’s Atacama desert. Think of the Atacama as a Mars analogue, while Zacatón reflects — at least in some respects — our exploratory needs on Europa. Autonomy is the key, operating unassisted in the remotest environments, and this work may one day ensure that when we do get to Europa, we’re up to the challenge.