by NASA is building a roadmap for robots that could visit ocean worlds through future space missions and break through the worlds’ thick, icy layers to explore subterranean seas in search of life.
Recently, the space agency revealed the results of a NASA-sponsored workshop held in February 2023 in which scientists and engineers met to discuss possible “cryobot” mission concepts. The idea is to traverse the icy exterior of the solar system’s moons, like JupiterMoon Europe or Enceladus, Saturn’s moon, and place a probe inside 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 a frozen ocean world that can melt ice and therefore slide down as that water flows around it and freezes again.
These probes, and the so-called “thermal drilling” technique, are currently commonly used to investigate glaciers and ice caps on Earth, but the icy layers of worlds like Europa and Enceladus are colder and thicker. They also exhibit behaviors that are much less predictable.
Exploiting current terrestrial thermal drilling operations in extraterrestrial environments through cryobots has been the focus of researchers supported by NASA’s Scientific Exploration Subsurface Access Mechanism for Europe (SESAME) and Concepts for Earth Sensing Technology programs. life on ocean worlds (COLDTech) for several years.
Related: Water ice moons that could host life infographic
However, over this time, humanity has learned much more about the ice-covered ocean worlds and, therefore, the workshop, held at the California Institute of Technology (Caltech), offered the opportunity to scientists involved in these projects to come together again and ensure these developments. are being taken into account in the robot’s mission architecture.
To find life, follow the water.
Life as we know it depends on many key compounds, molecules and elements, but arguably none are as vital as water.
As a fundamental building block of life here on Earth, it’s easy to see why water has become the focus of scientists searching for life elsewhere on the planet. Solar system. And while we’ve discovered that water is plentiful in our star courtyard (and even beyond), no discovery has been more tantalizing to us. astrobiologists than the understanding that the icy moons of our own solar system host vast oceans of liquid water.
The discovery that the arid landscape of Mars once flooded with water it offers the unquestionably exciting opportunity to discover remains of ancient life, but ocean moons like Europa and Enceladus offer the opportunity to discover worlds that are currently habitable and may even host real living things in their waters right now. Finding such living things, although they are probably microbial, would be revolutionary.
According to NASA, the Caltech workshop led to the identification of four key aspects that should inform the roadmap for the development of a robot explorer of extraterrestrial water worlds. Those aspects were power, thermal capacity, mobility and communication.
A robot that can put heat under pressure.
Of course, the miles-thick icy layers of our ocean world muses pose considerable challenges to missions seeking to search for life. That means that the heart of an ocean world exploring cryobots would need a nuclear power system that is capable of providing heat that can melt those many kilometers of ice, a system that is estimated to need around 10 kilowatts (kW) of power. This system would also have to be integrated into a structure that can survive the immense pressure of these deep alien seas.
There is some precedence in developing such a system, however complex it may seem.
The Cassini spacecraft, which explored Saturn and its moons before diving into the giant gasThe 2017 atmosphere carried a thermal energy system capable of generating 14 kW, more than the energy needed to melt kilometers of ice. Additionally, during the 1960s and 1970s, radioisotope thermoelectric generators (RTGs) were deployed to the bottom of the oceans here on Earth that could likely survive the pressures of Europa’s oceans.
But the futuristic cryobot would not only need protection from its environment; It would also be necessary to protect it from the heat it itself generates. This would require a thermal management system that can maintain a safe internal temperature for the robot by distributing heat to the environment.
One way to do this, scientists say, is by using 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 melted ice water between the cryobot and the surrounding environment.
While systems like this have already been produced, much more development is needed to prepare them for the Europa or Enceladus ice sheets.
Those ice sheets can also contain impurities like rock and salt that a robot would need additional systems to penetrate. This could be done by mechanical cutting, removing those impurities with high-pressure water jets, or even using a combination of both.
Of course, some obstacles, such as large solid rocks, blocks of salt, pockets of water, or even large voids in these ice sheets, might be immovable by these methods; Therefore, a cryobot would also have to be able to navigate its way underground. oceans. This would involve integrating a downward-facing sensor to observe obstacles, as well as a steering system, both of which have been developed in the past but have not yet been fully integrated into any type of working system here on Earth.
Scientists will also have to come up with ways to better identify obstacles in the ice sheets before developing a mission that embarks on an icy ocean moon, something the workshop identified as a high priority. the next Europe Clipper The mission, which will launch in 2024 and reach Europa’s icy Jovian moon in 2030, could be an integral part of this hazard research work.
Breaking the ice but not communication
Last but not least, the other main aspect of the robotic mission discussed at the Caltech workshop was a communication system that would allow vital data to be transported from a deep-diving marine exploration probe to a central unit located on the ice of the aim. ocean worlds.
On Earth, cryobots do this using fiber optic cables, but deploying them through ice on an alien world would require being sure that this ice does not break the cable. This is something that would be especially challenging on Enceladus’ active ice sheet, which can shift as plumes of ocean material burst through fissures, spraying into the ocean. moon atmosphere.
Kate Craft of the John Hopkins Applied Physics Laboratory (JPL) is investigating how ice cuts on ocean moons could affect a communications system embedded in the ice, while other teams are studying non-physical methods of transmitting data, such as use of radio frequencies. , acoustics and even magnetic fields to transmit data from the oceans through the alien ice to the surface.
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— Evidence of extraterrestrial life may exist in the fractures of icy moons around Jupiter and Saturn.
— Giant moon collision may have given rise to Saturn’s iconic rings, study suggests
While these were the four key elements of cryobots exploring the ocean world discussed by the 40 or so attendees at this workshop, other things were discussed, such as instruments that can sample and analyze collected liquids, ice anchoring systems to secure modules on the surface and Materials to coat the surface of the cryobot that will not corrode in foreign environments.
The overall outcome of the mission planning exercise was that there is a lot of work to do, but a cryobot mission to icy worlds in the solar system is feasible.
Ultimately, this means that finding life on other worlds is more plausible than ever.
