Author : Tronserve | Tuesday, 7 January 2020
CASEY STATION, Antarctica — Near a nice, big hole in the ice and beneath the stone gray, midday Antarctic summer skies, six Adélie penguins stared at six men toiling with tools. The chasm in the ice might have been an inviting entry to the krill-rich waters below. None of the members of the tuxedoed recon party dove into the hole, a square about six feet across. The risk of leopard seals was just too great. But had they leapt in, the penguins would have discovered not a seal, but a robot.
In November, scientists and engineers from NASA’s Jet Propulsion Laboratory successfully field tested Bruie — the “Buoyant Rover for Under-Ice Exploration” — beneath the ice of eastern Antarctica. The remotely operated rover was built to crawl along the underside of sea ice and ice shelves. These tests on Earth have a long-term goal of one day seeking evidence of life beneath the thick frozen shell covering Jupiter’s ocean moon of Europa. Beneath that ice is three times more liquid water than can be found in all the oceans on Earth.
It will be years before a spacecraft from Earth lands on Europa, which was most closely studied by NASA’s Galileo mission in the 1990s. The next robotic probe to visit that world will be Europa Clipper, scheduled to launch no sooner than 2025. When it arrives some years later, that spacecraft will orbit Jupiter and encounter Europa dozens of times at different angles to thoroughly scan and map the moon, considered one of the best candidates in our solar system to be inhabited by some form of extraterrestrial life.
Any future for a lander visiting the Jovian moon is uncertain. But that hasn’t stopped NASA’s engineers and scientists from developing technologies to aid its mission.
“Getting a vehicle like the buoyant rover and other submersibles in the ocean of Europa is the long-term vision for what we hope to one day accomplish,” said Kevin Peter Hand, the project’s science lead from the Jet Propulsion Laboratory. “It’s going to come after Clipper and a lander on the surface. These precursor missions would set the stage for getting through the ice and reaching the ocean.”
Bruie has been in development since 2017. The rover is the marriage of Jules Verne-like inventiveness and the simplest machine possible to build: little more than an axle and two wheels, each about the size of a large pizza. As its expanded name implies, Bruie floats. The sea presses it against the belly of the ice shelf, and as the rover crawls along, its sensors collect data. During its Antarctic field tests beneath the ice of O’Brien Bay near Casey Station, an Australian base on the eastern part of the continent, the rover successfully endured three frigid three-hour deployments.
A fourth, critical test kept it submerged beneath the ice for 42 hours and 30 minutes. Andy Klesh, the project’s lead engineer, drove the rover using a laptop. While the rover can be piloted via satellite connection, during this mission, Dan Berisford, a mechanical engineer, carefully fed it a thin yellow tether.
The submerged rover crawled slowly but ably. An onboard camera streamed video to the laptop and revealed an Antarctica even more alien than the surface. Except for the curious penguins, the continent is stark and largely lifeless clear to the horizon. But a few feet below, the rover found vast brown webs of sea algae clinging to the ice. Fish would swim up and nibble away at it. Bubbles of oxygen accumulated as photosynthesis pumped away.
On Europa, the real action is in its ocean; if at last the Jovian moon does get a rover that could get beneath its surface, it makes sense that the robot would crawl on the underside of its ice shell. The radiation chemistry and geophysics of Europa’s surface might provide a mechanism for providing oxygen for life in its depths.
To study such life, any undersea rover would need to be noninvasive.“While the thrusters of a normal underwater remote-operated vehicle can jet-blast delicate algaes off the bottom of ice sheets during close encounters, Bruie gently tiptoes beneath them,” said Daniel Arthur, a technologist who works with Caltech and the University of Western Australia.
The rover analyzes the ice-ocean interface passively and at consistent distances, drawing little power — especially relative to submarine-type drones. “Power will be in short supply on Europa,” Dr. Arthur said, “and we don’t want a propeller obliterating humanity’s first encounter with extraterrestrial life.”
The ice-ocean interface on Earth is a zone where physics, chemistry, and biology all interact, said Alison Murray, an Antarctic scientist at the Desert Research Institute in Nevada. On our planet, the zone is rich with microorganisms. “We want to understand the habitability of these interfaces as well as the diversity of life that calls them home,” said Dr. Murray. “In both cases, we can better understand whether this interface in the dark waters of Europa might actually be able to support life.”
Dr. Hand hopes that work on devices like Bruie can drive development of robots to explore Earth’s cryosphere, where ice meets oceans. “It is my hope that exploring Europa’s ocean can serve as a forcing function, from an engineering standpoint, to build those kinds of capabilities to get the same work done on planet Earth,” he said.