The conditions needed for life to survive include several key factors:
- Liquid Water: Essential as a solvent for chemical reactions, water allows substances to dissolve and interact freely, which is critical for metabolism and cellular processes
- Source of Energy: Life requires energy to fuel metabolic reactions. This energy can come from sunlight (photosynthesis) or chemical sources (redox chemistry)
- Organic Molecules and Nutrients: Life depends on organic molecules as building blocks and nutrients to sustain growth and reproduction. Nutrients can be obtained from the environment or through biochemical cycles like volcanic activity
- Suitable Temperature Range: Water must remain liquid, so temperatures generally need to be between about 15°C and 115°C (59°F to 239°F) to avoid freezing or vaporization, providing a stable environment for life’s chemistry
- Protective Atmosphere: An atmosphere that shields from harmful radiation while maintaining warmth is important to sustain life on a planet
- Stable Environment: Life needs a reasonably stable environment that supports evolutionary processes, including appropriate pressure and chemical conditions
- Additional Human-Specific Needs: For human survival, air (oxygen), shelter, sanitation, sleep, and personal space are also critical physiological requirements
- Tolerance to Extremes: Some life forms, called extremophiles, can survive in harsh conditions such as extreme temperatures, pressures, acidity, or salinity, expanding the range of possible habitats for life
In summary, life requires liquid water, a source of energy, organic nutrients, a suitable temperature range, a protective atmosphere, and a stable environment to survive and evolve. For humans, additional needs like oxygen, shelter, and sleep are vital