NASA has recently announced US$600,000 (£495,000) in funding for a study to the feasibility of sending swarms of miniature swimming robots (known as independent microswimmers) to explore oceans beneath the icy shells of our solar system’s many “ocean worlds”. But don’t imagine metallic humanoids swimming frog-like underwater. They will probably be simple, triangular wedges.
Pluto is an example of a probable ocean world. But the worlds with oceans closest to the surface, making them the most accessible, are Europa, a moon of Jupiter, and Enceladus, a moon of Saturn.
Living in Ocean Worlds
These oceans are of interest to scientists not only because they contain so much liquid water (Europe’s ocean probably has about twice as much water like the whole oceans of the earth), but because chemical interactions between rock and the ocean water could support life. In fact, the environment in these oceans can be very similar to that on Earth when life began.
These are environments where water that has seeped into rock from the ocean floor becomes hot and chemically enriched — water that is then expelled back into the ocean. Microbes can feed on this chemical energy, and can in turn be eaten by larger organisms. There is actually no need for sunlight or atmosphere. Many of these warm, rocky structures, known as “hydrothermal vents,” have been documented on Earth’s ocean floors since they were discovered in 1977† In these locations, the local food web is indeed supported by chemosynthesis (energy from chemical reactions) instead of photosynthesis (energy from sunlight).
In most of our solar system’s ocean worlds, the energy that warms their rocky interiors and prevents the oceans from freezing down to the base comes mainly from tides. This is in contrast to the largely radioactive heating of the Earth’s interior. But the chemistry of the water-rock interactions is similar.
Enceladus’s ocean has already been sampled by flying the Cassini spacecraft through plumes of ice crystals that erupt through cracks in the ice. And there’s hope that NASA’s Europe Clipper Mission may find similar plumes to sample when it begins a series of dense Europa flybys in 2030. However, going out into the ocean to explore could be much more informative than just sniffing a freeze-dried sample.
In the swimming pool
This is where the sensing with independent micro swimmers (Swim) understanding comes. The idea is to land on Europa or Enceladus (which would be neither cheap nor easy) in a place where the ice is relatively thin (not yet located) and use a radioactively heated probe to cut a 25cm wide hole through the ice. ocean – hundreds or thousands of feet below.
Once there, it would release up to about four dozen 12-inch-long, wedge-shaped microswimmers to explore. Their endurance would be much less than that of the 3.6m autonomous underwater vehicle of the famous name Boaty McBoatfacewith a range of 2,000 km that has already reached a cruise of more than 100 km under the Antarctic ice.
At this stage, Swim is just one of five “phase 2 studies” into a series of “advanced concepts” to be launched in NASA’s 2022 round. Innovative Advanced Concepts (NIAC) program† So there’s still a good chance Swim will become a reality, and no full mission has been mapped out or funded.
The microswimmers would communicate with the probe acoustically (via sound waves), and the probe would send its data via a cable to the lander on the surface. The study will test prototypes in a test tank in which all subsystems are integrated.
Any micro swimmer could explore perhaps only tens of meters from the probe, limited by their battery power and the range of their acoustic data link, but acting as a couple allowed them to map changes (in time or location) in temperature and salinity. They may even be able to detect changes in the turbidity of the waterwhich could indicate the direction to the nearest hydrothermal vent.
Power limitations of the micro swimmers may mean none of them can carry cameras (these need their own light source) or sensors that can specifically sniff out organic molecules. But nothing is excluded at this stage.
I think finding signs of hot water craters however, is a bull’s eye. The ocean after all, the floor would be many kilometers lower than the release point of the micro swimmer. But to be fair, locating vents is not explicitly suggested in the Swim proposal. To locate and examine the vents ourselves, we’ll probably need Boaty McBoatface in space. That said, swimming would be a good start.
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Quote: NASA considers sending swimming robots to habitable ‘ocean worlds’ of the solar system (2022, July 5), retrieved July 5, 2022 from https://phys.org/news/2022-07-nasa-robots-habitable-ocean- worlds .html
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