Habitability
Habitability asks what physical and chemical conditions can support long-lived environments suitable for life as we know it.
Liquid waterSurface or subsurface liquid water is a central criterion for familiar biochemistry.
EnergyStars, chemistry, tides and internal heat can provide usable energy sources.
Atmosphere and climateLong-term climate stability depends on atmospheric composition and planetary feedbacks.
Not a guaranteeA potentially habitable environment is not evidence that life is present.