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Mars
Solar System
A once-water-rich planet with ancient rivers and lakes, persistent ground ice, and the most accessible extraterrestrial rock record.
AEvidence classDirectly observed or repeatedly measured
- Mean radius
- 3,389.5 km
- Surface gravity
- 3.721 m/s²
- Representative temperature
- about −63 °C global mean
- Surface pressure
- about 6.1 mbar mean
Scientific assessment
Present surface conditions are hostile, but ancient habitable environments are well documented and can be sampled directly by landed missions.
- Liquid-water evidence
- Ancient rivers and lakes; present ice and transient brines debated
- Principal constraint
- Radiation, aridity, and low pressure
- Principal mission context
- Mars orbital and landed mission fleet
Comparative evidence matrix
A transparent research-priority index, not a probability of life. It combines solvent evidence, usable energy, chemistry, environmental stability, evidence maturity, and sampling access.