NASA is working on a roadmap for robots that could visit ocean worlds via future space missions and crack the world’s thick, icy shells to explore subterranean seas in search of life.
Recently, the space agency unveiled the results of a NASA-sponsored workshop held in February 2023 that brought together scientists and engineers to discuss potential “cryobot” mission concepts. The idea is to break through the icy exterior of the solar system’s moons Jupiter‘s moon Europe or Saturn’s moon Enceladus, and drop a probe inside it that can explore the underlying liquid ocean.
The cryobot concept explored is an alternative to simply drilling into a world, and involves the use of a cylindrical device sent from a mother unit on the surface of an icy ocean world that can melt ice and therefore slide down as water flows around it and restarts freezes.
These probes and this so-called ‘thermal drilling technique’ are currently commonly used to explore glaciers and ice caps on Earth, but the icy shells of worlds like Europa and Enceladus are colder and thicker. They also exhibit behavior that is much less predictable.
Deploying current thermal drilling operations on Earth to extraterrestrial environments via cryobots has been the focus for years of researchers supported by NASA’s Scientific Exploration Subsurface Access Mechanism for Europa (SESAME) and Concepts for Ocean Worlds Life Detection Technology (COLDTech) programs.
Related: Icy water moons that may harbor life (Infographic)
Over this time, however, humanity has learned much more about ice-covered ocean worlds, and so the workshop, held at the California Institute of Technology (Caltech), provided an opportunity for scientists involved in these projects to revisit these developments to gather and guarantee. are included in the architecture of robot missions.
Follow the water to find life
Life as we know it depends on many important compounds, molecules and elements, but none are as important as water.
It is a fundamental building for life here on Earth. It’s easy to see why water has become the focus of scientists looking for life elsewhere in the world. solar system. And while we’ve discovered that water is plentiful in our beautiful backyard (and even beyond), no discovery has been more tempting to us. astrobiologists then the realization that icy moons in our own solar system harbor enormous oceans of liquid water.
The discovery of what made the arid landscape Mars once flooded with water offers the undeniably exciting opportunity to explore remains of ancient life, but ocean moons like Europa and Enceladus offer the chance to discover worlds that are currently habitable and may even currently host actual living creatures in their waters. Those living things, even though they are probably microbial, would be revolutionary to find.
According to NASA, the Caltech workshop led to the identification of four key aspects that should set the roadmap for the development of a robot that explores the alien water world. Those aspects were power, thermal capacity, mobility and communications.
A bone that can pressurize the heat
Of course, the miles-thick icy shells of our ocean-world muses pose significant challenges to missions searching for life. That means the heart of an ocean world that cryobot explores will need a nuclear power system that can provide heat that can melt through those many miles of ice—a system estimated to require about 10 kiloWatts (kW) of energy. This system would also need to be integrated into a structure that can survive the immense pressure of these deep alien seas.
There is some priority in developing such a system, no matter how complex it may sound.
The Cassini spacecraft, which conducted research Saturn and its mane before they settle into the gas giantThe 2017 atmosphere contained a thermal energy system that could generate 14 kW – more than the energy needed to melt through kilometers of ice. Also, in the 1960s and 1970s, radioisotope thermoelectric generators (RTGs), which could probably survive the pressure of Europe’s oceans, were deployed at the bottom of the oceans here on Earth.
But the futuristic cryobot wouldn’t just need protection from its environment; it should also be protected from the heat it itself generates. This would require a thermal management system that can maintain a safe internal temperature for the bot by distributing heat to the environment.
One way to do this, scientists say, is to use two independently pumped fluid circuits. One would circulate an internal working fluid through channels embedded in the robot’s skin, and the other would circulate molten ice water between the cryobot and the environment.
Although these types of systems have already been produced, much more development is needed to prepare them for the ice shells of Europa or Enceladus.
Those ice shells can also contain impurities such as rock and salt, which require additional systems for a robot to penetrate. This can be done through mechanical cutting, by blowing away those impurities with high-pressure water jets, or even by using a combination of both.
Of course, some obstacles, such as large and massive rocks, salt blocks, water pockets, or even huge voids in these icy shells, cannot be removed with these methods. A cryobot should therefore also be able to navigate its passage to the subsurface. oceans. This would involve the integration of a downward-facing sensor to observe the obstacles, as well as a steering system, both of which have been developed in the past but have yet to be fully integrated into any kind of work system here on Earth.
Scientists will also need to figure out ways to better identify obstacles in ice shells before developing a mission to an icy ocean moon, something the workshop identified as a high priority. The following Europa Clipper The mission, which will launch in 2024 and arrive at Europa’s icy moon Jupiter in 2030, could be an integral part of this hazard investigation.
Breaking the ice, but no communication
Last but not least, the other primary aspect of the robotic mission discussed at the Caltech workshop was a communications system that would allow vital data to be relayed from a deep-diving, sea-exploring probe to a mother hub unit that sat atop the ice of targeted missions. ocean worlds.
On Earth, cryobots do this using fiber optic cables, but if you want to deploy them through ice on an alien world, you need to be sure that the ice doesn’t break the cable. This is something that would be especially challenging in Enceladus’ active ice sheet, which can shift and move as plumes of ocean material erupt through fissures and spill into the ocean. the moon’s atmosphere.
Kate Craft of the John Hopkins Applied Physics Laboratory (JPL) is investigating how ice scissors on ocean moons could affect a system of communications cables embedded in ice, while other teams are looking at non-physical methods of data transmission, such as the use of radio frequencies. , acoustics and even magnetic fields to transmit data from oceans through the alien ice to the surface.
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While these were the four key elements of exploring cryobots in the ocean world discussed by the approximately 40 participants in this workshop, other issues were also looked at, such as instruments that can sample and analyze collected fluids, ice anchoring systems to support modules surface, and materials to cover the surface of the cryobot that will not corrode in alien environments.
The overall outcome of the mission planning was that there is still much work to be done, but a cryobot mission to icy worlds of the solar system is feasible.
This ultimately means that finding life on other worlds is more plausible than ever before.