Knowra Planetary habitability Planetary habitability Planetary habitability is the capacity of a planet or moon to support life. It depends on conditions such as liquid water, usable energy, and suitable chemistry.
Habitable zone : The range of orbital distances where a planet could maintain liquid water on its surface under suitable atmospheric conditions. It estimates whether stellar heating permits surface water, but does not establish that life can exist.
Greenhouse effect : Warming that occurs when atmospheric gases absorb and re-emit infrared radiation emitted by a planet's surface. It can keep surface water liquid beyond the range predicted from sunlight alone.
Earth : The third planet from the Sun and the only world known to support life. Earth is the sole confirmed example of a habitable world and a reference for habitability criteria.
Astrobiological habitability : The potential of an environment to support life, assessed through physical, chemical, and biological conditions. This is the broad environmental question; it does not require detecting organisms.
M-dwarf habitability : The study of whether planets orbiting small, cool M-dwarf stars can support life. Close-in habitable-zone planets may face intense flares, tidal locking, and atmospheric loss.
Liquid water : Water in its liquid state, stable when temperature and pressure fall within a particular range. Surface liquid water is a familiar habitability criterion, though subsurface oceans can also matter.
Carbonate–silicate cycle : A long-term geochemical cycle linking atmospheric carbon dioxide, silicate weathering, carbonate formation, and volcanic outgassing. On Earth, it helps regulate climate over geological timescales as stellar brightness changes.
Mars : The fourth planet from the Sun, a cold desert world with evidence of ancient rivers, lakes, and other flowing water. Its past environments test whether habitability can precede long-term surface dryness.
Biosignature : A measurable feature that may indicate past or present life, though nonbiological processes can sometimes produce it. A potentially habitable environment is not itself evidence of life; biosignatures address detection.
Subsurface ocean : A body of liquid water beneath the solid exterior of a planet or moon. Such oceans may be widespread, but their energy sources and exchange with surfaces remain uncertain.
Show all 28