Within astrobiology, Freeman Dyson is a figure that looms large, especially because of his concept of a Dyson swarm, the idea that an advanced alien civilization could surround their star with energy collectors and harvest as much of its energy as they wanted. This stands in contrast to a so-called Dyson sphere, which actually stems from science fiction author Olaf Stapledon in the 1930s, which would harvest all harvestable energy from a star by fully enclosing it, but that may never be feasible. Dyson’s swarm, however, is, and we’re already building one with our solar orbiting probes, both past,
Dyson has also envisioned a species that may never be advanced, or even intelligent, yet might also harvest its energy from a star in a somewhat similar way. One can argue that photosynthesizing earth life does exactly that, but it does it within the constraints of an atmosphere that can retain enough heat to keep water liquid. But this kind of a situation for liquid water may not be the most common occurence of liquid water in the galaxy at large. It certainly isn’t for our solar system.
While it’s possible that there was once three water worlds in this system, Earth, Venus, and Mars, there is now only one with stable surface liquid water. Yet there are many moons in this solar system that are suspected of having subsurface liquid water locked under ice. At least one of these, specifically Europa, seems to have everything it needs for life to have hypothetically gotten started in that Ocean. The big question, however, is what evolution could occur inside this ocean. One side of the argument is not much, and that such life would forever remain simple and microbial. Standing for this is that it took a seriously long time for earth life to make the leap from prokaryotic life to eukaryotic life and that the conditions inside Europa’s oceans might not be as ideal for that to ever happen. Standing against that is earth’s life, which has shown itself to be ridiculously resilient.
The more we look into life on this planet, the more surprising it is with organisms capable of surviving enormous doses of radiation to the ability to survive completely drying out. If that’s the case for life in the universe in general, then things may be able to happen in ice shell moons that may surprise us. While we have no real idea what life elsewhere in the universe might be like, Dyson envisioned one hypothetical possibility regarding ice shell moons.
Called Dyson’s Sunflowers, these organisms would originate deep in an ice shell moon, and retain roots in the liquid ocean for nutrition. It then might evolve to move upward within cracks in the ice and eventually break the surface. If so, it can be envisioned that such a creature might take advantage, of heat and sunlight, perhaps through evolving high reflectivity that can concentrate it. This would, at least with the ice moons of our solar system, require the organism to be able to at least partially survive in space. That’s a very tall order for most of earth’s life, though the tardigrades show that it can be survivable. But it’s never ideal for anything living here, so Dyson’s sunflowers would have to partially evolve in space specific to those conditions, which has not been seen with earth life and may not be possible.
But if it were, Dyson notes that such a creature might eventually evolve to break ties with its roots, and move on to live directly in space, perhaps sustaining itself by colonizing asteroids. In astrobiology, this seems one of the bigger stretches, space is a really harsh place, but since we don’t yet know the rules of what life on other worlds can do, it’s an interesting concept nonetheless.