It's robotic,
aquatic and ramping up for a long, deep dive, all to test technology that could
one day allow its autonomous descendants plunging into alien waters believed to
sit beneath the icy crust of Jupiter's
moon Europa.
Built by
Texas-based Stone Aerospace, the autonomous underwater vehicle Deep Phreatic
Thermal eXplorer (DEPTHX) will begin a second round of dives this week to
explore the depths of La Pilita, a 377-foot (115-meter) deep geothermal
sinkhole in Mexico [image].
They follow a series of successful tests dives to shakedown the vehicle's
autonomous navigation and mapping capabilities, researchers said [video].
"The fact
that it did it and came home each time, it's like the clouds parted," said
Stone Aerospace chief Bill Stone, DEPTHX principal investigator, of the robot's
early success. "I've been doing this 27 years and I was blown away."
Stone and
his team are priming DEPTHX to take the ultimate dive down El Zacatón, a
water-filled geothermal sinkhole - or cenote - in Mexico known to reach depths
beyond 925 feet (282 meters), though its true bottom has not been
detected by either human divers, robots or sonar [image].
That expedition is slated for May.
The
research is part of a $5 million NASA
study to develop technology that could one day allow a waterborne
explorer to probe the vast unknown ocean thought to lurk beneath the miles-thick
crust of ice covering Europa. The cracked,
icy Jovian moon has been billed one of the solar systems' best
hunting grounds for extraterrestrial organisms.
Researchers at Stone Aerospace, Carnegie Mellon University, the Colorado School of Mines, University of Colorado and Southwest Research Institute are participating in the DEPTHX project, which is funded by the Astrobiology Science and Technology for Exploring Planets program within NASA's science directorate.
Diving
deep
Despite
weighing in at a hefty 1.3 tons, DEPTHX's design keeps it neutrally buoyant in
water, allowing the 8.2-foot (2.5-meter) wide robot to maneuver in three
dimensions (up, down and side-to-side) with the aid of six thrusters [image].
Because no one knows for sure how deep the El Zacatón cenote goes, the vehicle
has been built to dive to a depth of about 3,280 feet (1,000 meters),
Stone said.
DEPTHX is
armed with 36 onboard computers, 56 sonar sensors and a suite of depth,
guidance and velocity sensors to find its way through the murky waters of La
Pilita or El Zacatón.
But the
brass ring of DEPTHX's guidance system is its Simultaneous Localization and
Mapping (SLAM) system, navigation software designed to allow the robot to
autonomous take its sonar and other sensor readings to build reliable and
useful three-dimensional maps of unexplored terrain.
"It's kind
of the chicken and the egg," said DEPTHX project scientist George Kantor, of Carnegie Mellon University where
researchers developed the robot's SLAM software. "As it builds the map,
it can actually use that map as it moves around."
Early tests
DEPTHX tests 3-D mapping system revealed an underwater tunnel 98 feet (30
meters) below the surface of the 98-foot (30-meter) wide La Pilita
cenote, though the system should be put through its paces in full in the
upcoming tests, Kantor said. Other autonomous tests using dead reckoning and
sonar navigation have proven successful, he added.
"When
you're working on Europa....there is not going to be any guidance from Mission
Control," Stone said. "They're all going to be sitting back there sweating, and
hoping they didn't mess up some line of code."
NASA
demonstrated as much last
week when its New Horizons probe swung
past by Jupiter on Feb. 28, relying on a series of preloaded commands to
study the planet and its moons due to
the 45 minutes it would take a signal to cross the millions of miles between Earth and the gas
giant.
DEPTHX's
navigation system complexity also comes at a cost, researchers said.
"Our
cruising speed is about 0.2 meters per second (about half a mile per hour),"
Kantor said. "That's not going to work on Europa, where you're going to want to
be moving a lot faster."
Science
automaton
Finding your way
around obstacles or rocky walls in a pitch-black cenote - or the waters of
Europa, for that matter - is just the first step for DEPTHX researchers, who
are hoping to develop autonomous science capabilities for the aquatic robot -
especially those useful for studying microbiology.
"The hat
trick beyond what we've already done is to give it the ability to sniff out
environmental variables, gradients in the environment's chemistry, that would
suggest something is going on," Stone said.
DEPTHX
carries a probe-like appendage [image]
capable of retrieving solid samples during dives and contains space for up to
five two-liter water samples from different locations around cenotes like La
Pilita or El Zacatón. The robot also sports cameras to scan for color changes
in rock walls and an onboard microscope to detect moving cells, a hallmark of
living microorganisms, researchers said.
"There is
absolutely no way of knowing what's in this hole," DEPTHX's chief
microbiologist John Spear, of the Colorado School of Mines, told SPACE.com
of El Zacatón.
For Spear,
DEPTHX's potential as a pathfinder for a Europa probe is a bit of a bonus. The
robot's technology could also be adapted to explore any number of environments
on Earth, from the depths of the planet's oceans to the deep lake bottoms below
Antarctica.
The key,
Spear added, is developing the capability of overlaying science observations -
such as changes in water sulfide content - with SLAM location maps to pinpoint
their respective positions.
"When you
walk up to a hot spring, you see it, you smell it, you can feel it and taste
it," Spear said. "We needed to develop a machine that's capable of doing the
same thing I can. We had to give the machine senses so to speak."
For Stone,
DEPTHX's big test comes in May, when the robot will put its navigation and
science capabilities to the test at El Zacatón.
"The two goals
are there," Stone said. "I think we're going to hit them."
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