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Why has Earth’s atmosphere been able to keep water as solid, liquid, and gas?

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Wispy cirrus clouds stretch across a bright blue sky above trees and a river at Pinawa Dam Provincial Park in Manitoba, Canada, with sunlight illuminating the scene. — Atmosphere The atmospheres of planets in the solar system are composed of various gases, particulates, and liquids. They are also dynamic places that redistribute heat and other forms of energy. On Earth, the atmosphere provides critical ingredients for living things. Here, feathery cirrus clouds drift across the deep blue sky over Pinawa Dam Provincial Park, near Pinawa, Manitoba, Canada.

Earth’s ability to maintain water in solid, liquid, and gaseous phases is primarily due to its gravitational attraction and its specific surface temperature, which is regulated by the greenhouse effect.123

Because Earth has sufficient mass, its gravitational pull is strong enough to retain an atmosphere that prevents water vapour from escaping into space. Furthermore, the planet's temperature is maintained at a level that allows water to exist in all three states. The greenhouse effect—driven by natural constituents like water vapour and carbon dioxide—keeps the surface warm enough to prevent the planet from being entirely frozen, while the cold trap in the upper atmosphere (at about 15 km) prevents most water vapour from reaching high altitudes where it could be destroyed by ultraviolet radiation. This balance of temperature and gravity ensures that water can cycle through the hydrosphere as ice, liquid water, and vapour, which is essential for sustaining life.1324