Which planet has an atmosphere that allows water to exist in all three states?

Earth is the only planet in our solar system with an atmosphere and conditions that allow water to exist in all three states: solid (ice), liquid (water), and gas (water vapor). This capability is crucial for maintaining life as we know it and is primarily due to Earth's optimal distance from the sun, which places it within the "Goldilocks Zone" where temperatures are just right.

Earth's atmosphere is composed of a mix of gases, including nitrogen and oxygen, which play essential roles in regulating temperature and supporting the water cycle. This cycle ensures that water can evaporate into vapor, condense into clouds, and precipitate as rain or snow, allowing water to transition between solid, liquid, and gas states naturally over various climates.

Other planets have extreme conditions or lack the necessary atmospheric composition to support the presence of water in all forms. For example, Mars has a thin atmosphere that prevents stable liquid water from existing on its surface. Jupiter possesses a thick atmosphere of hydrogen and helium, which is not conducive to the presence of water in its various states as seen on Earth. Venus has high atmospheric pressure and temperatures that cause water to exist only in vapor form, making it impossible for liquid water to survive.