How to colonize icy planets with subsurface liquid water (Titan, Callisto, Ganymede, Europa, Ceres, Enceladus)?
TLDR: How would humanity colonize icy moons of Gas Giants?
It's the future. Mars has been successfully colonized. Since the completion of the carbon nanotube space elevator 100 years ago, Mars' route capacity greatly increased and new settlements flourished. The United States of Mars is now a prosperous independent planet. Terraforming will still take centuries to transform Mars into a fully habitable planet and human colonies will be confined for a while to domes providing air, water, food and protection from cosmic rays.
Venus' atmosphere has also been colonized, floating aerostat glide in the Venusian atmosphere at 50 km altitude where the temperature is around 280K, circling the planet every 96 earth hours. These aerostats are filled with breathable air similar to that found on earth. Breathable air is a lifting gas on Venus (like helium on Earth) and it can lift entire research lab colonies. The upper atmosphere of Venus protects the settlements from cosmic rays. Those colonies are mostly used for scientific missions because large-scale floating settlements are impractical. Terraforming Venus will take even longer than terraforming Mars, getting rid of the crushing 93 bar atmosphere and decreasing the 750 K temperature will require technologies and energy levels that we haven't mastered yet.
Asteroids in the Asteroid Belt have been colonized mostly for mining. Some of these asteroids have rare metals but apart from automated mining factories, there's not much interest in settling on those tiny objects.
The United States of Earth is looking for new challenges to foster humanity and wants to colonize planets beyond the asteroid belt.
After decades of probing, scientists' consensus is that a layer of liquid water exists deep beneath the icy surface of Titan, Callisto, Ganymede, Europa, Ceres and Enceladus. That heat from tidal flexing and the inner core allows the subsurface ocean to remain liquid.
The liquid ocean on these icy moons is estimated to be at least 10 km below the frozen ice surface. Surface temperature is a chilling 100K, the atmosphere is almost non-existent, gravity is very low, cosmic ray radiation is quite high. These rocks are much harder to colonize than Venus or Mars but that won't stop us right? The question is how would we establish colonies on these planets?