Apart from terraforming, there are several ways humans could potentially live on another planet:
Space habitats: Rather than living directly on the surface of a planet, humans could construct self-contained habitats in space. These habitats could be in the form of rotating space stations or large spacecraft designed to support long-term habitation. They would provide a controlled environment with artificial gravity, life support systems, and protection from radiation.
Underground colonies: Building underground colonies or habitats on other planets or moons could provide natural protection from harsh surface conditions, such as extreme temperatures, radiation, and micrometeorite impacts. These underground habitats could utilize existing caves or be created by drilling and excavating.
Floating cities: On planets with dense atmospheres, such as Venus, it might be possible to create floating cities in the upper atmosphere. These cities would be suspended by using buoyant materials, taking advantage of the atmospheric pressure to provide habitable conditions.
Sealed habitats: Humans could establish sealed habitats on the surface of other planets or moons, similar to biodomes. These self-contained structures would maintain a controlled environment, including temperature, air quality, and water supply, protecting inhabitants from the hostile external conditions.
Mobile settlements: Rather than staying in fixed locations, humans could establish mobile settlements on other celestial bodies. These settlements could be in the form of roving vehicles or modular structures that can move and explore the planet, seeking resources and adapting to changing conditions.
Genetic modification and adaptation: If humans were to colonize another planet with different environmental conditions, genetic modification or bioengineering could be used to enhance human adaptability. This could involve altering our physiology, metabolism, or immune systems to better cope with the specific challenges of the new environment.
It's important to note that many of these ideas are still in the realm of speculation and would require significant technological advancements before they could be realized. However, as our understanding of space exploration and habitation improves, these concepts may become more feasible in the future.