Astrobiologists chasing extraterrestrial life estimate that significant amounts of water are buried in several moons within the solar system. Jupiter's moons Europa and Ganymede, as well as Saturn's moon Enceladus, are noted as typical candidates. The surfaces of these moons are covered with thick layers of ice, beneath which a salty ocean is presumed to exist. The United States and Europe are sending various spacecraft to search for traces of water on solar system planets and moons while also pushing ahead with plans to directly penetrate the ice layers.
According to The Telegraph, the National Aeronautics and Space Administration (NASA) recently developed an underwater exploration robot capable of navigating through the oceans beneath the ice layers of Jupiter and Mars' moons while searching for signs of life, and it successfully passed recent underwater tests. Although unmanned probe vehicles have been developed for exploring the Earth's seabed, this marks the first development of an underwater robot that can operate in oceans on extraterrestrial bodies.
Research to date suggests that Jupiter's moon Europa contains significantly more water than all of Earth's oceans combined. Evidence of geological activity that supplies heat to the ocean and generates nutrients necessary for life has been discovered on Europa. Scientists say that to find life beyond Earth, tracking traces of water is essential. However, the areas beneath the ice layers of the solar system's moons remain inaccessible to human eyes and feet.
NASA has been promoting a program called 'Independent swimming robot for monitoring' (SWIM), investing $725,000 (about 1 billion won) since 2021. Although the development budget is not large, the goals of this plan are ambitious. The concept involves using a cylindrical thermal drilling device powered by nuclear energy to penetrate the thick ice layers of Mars and Jupiter's moons while deploying multiple underwater robots into the oceans.
This miniature underwater robot measures 42 cm in length and weighs 2.3 kg. It has a wedge shape created through 3D printing. Tests conducted at a swimming pool at the California Institute of Technology in Pasadena, Southern California, since September showed that it is operating normally. NASA engineers plan to reduce the size of this robot to one-third, making it as small as a cellphone.
Previously, NASA had revealed plans for the operation of a thermal drilling device called the 'Cryobot' designed to pierce the ice layers of moons like Europa and Enceladus last December. This cylindrical device, launched from a probe mothership that lands on the ice layer, works on the principle of sliding down while melting the ice with heat. The necessary heat to penetrate the ice is obtained from a small reactor rated at 10 kilowatts (kW).
In simulations conducted by researchers, sending 40 robots inside a thermal drilling drill with a diameter of 25 cm allows exploration of 278,000 cubic meters under the ocean while traveling in groups for two hours. Lee Sun-shall, a NASA researcher, noted, "There is a vast salty ocean beneath the ice layer of Europa, containing essential components for life, such as various energy sources and compounds," adding that "these miniature underwater robots could explore a much larger area by traveling in groups."
The miniature underwater robot contains a multipurpose chip developed by the Georgia Institute of Technology. This chip measures temperature, pressure, acidity, alkalinity, conductivity, and chemical composition. In tests conducted last July under glaciers in Juno, Alaska, the robot was successfully deployed through drill holes in the ice to measure pressure and conductivity at depths of 50 meters.
The information collected by the robots is transmitted to the Cryobot through an underwater communication device similar to sonar. The Cryobot then sends this information through the ice crust to a probe on the Moon's surface, which is subsequently relayed to Earth.
Underwater exploration robots are already being used to investigate the deep sea and glaciers on Earth. Scientists expect that the environments beneath the ice layers of Europa and Enceladus will be even colder and more hostile. Underwater exploration robots will have to navigate these conditions while enduring high pressures in the dark seabed. Research Institute Lee remarked at a conference held last year, "Making underwater robots small is difficult, and achieving underwater communication remains a significant challenge," emphasizing that "reaching Jupiter's moons, located more than 600 million km away from Earth, also poses an enormous task."
The research team is awaiting data from the Jupiter-bound Europa Clipper, which was launched last October. This spacecraft is expected to arrive at Jupiter in 2030 and, starting the following year, will conduct 49 gravity-assist flybys, collecting high-resolution observational data while orbiting around 2.5 km above Europa. The research team is also anticipating information from the Jupiter Icy Moons Explorer (JUICE) launched by the European Space Agency (ESA) last year. This spacecraft is expected to arrive at Jupiter in 2034 and explore three moons: Ganymede, Callisto, and Europa, which are presumed to have a gigantic ocean beneath their surfaces. NASA plans to deploy the miniature underwater robots immediately if these spacecraft detect conditions suitable for life within the ice layers of the moons.
Reference materials
NASA (2024), https://www.jpl.nasa.gov/news/nasa-ocean-world-explorers-have-to-swim-before-they-can-fly/
NASA (2023), https://science.nasa.gov/science-research/science-enabling-technology/digging-deeper-to-find-life-on-ocean-worlds/