Which planet is the only one known to support life?

Earth is the only planet currently known to support life. It has liquid surface water, a nitrogen-rich atmosphere, a protective magnetic field, and temperatures that allow complex chemistry to persist.

Life on Earth occupies environments ranging from ocean trenches to high mountain lakes and deep rock beneath the surface. Scientists have confirmed no life beyond Earth, although the search continues. Mars once had flowing water and may still contain habitable environments underground, while Jupiter’s moon Europa and Saturn’s moon Enceladus have subsurface oceans that are considered promising places to investigate.

The wording “known to support life” matters. It does not claim that Earth is necessarily the only living world in the universe; it means Earth is the only planet for which life has been directly confirmed. Venus, despite being similar to Earth in size, has an extremely hot, high-pressure surface and corrosive clouds.

Earth is also the only planet in the Solar System with a large, stable biosphere known to science. Its natural satellite, the Moon, is not a planet and has no confirmed life.