Earth is the only known planet with liquid water.
Because on most planets (mars being an exeption as there are places where water can stay liquid) temperature and/or atmospheric pressure is to high or low for water to stay liquid.
Earth!
Mars
The abundance of liquid water indicates a favorable environment for life as we know it, as it is essential for biological processes. It also suggests stable temperatures and pressures that allow water to remain in its liquid state, which can influence climate and geological activity. Additionally, the presence of liquid water can signify potential for ecosystems, biodiversity, and the possibility of extraterrestrial life on other planets.
The planet Mars is believed to be in the appropriate distance from the Sun to have liquid water. It is located within the habitable zone of our solar system, where conditions could allow for water to exist in liquid form under the right circumstances.
None of the planets in our solar system except Earth are thought to have surface liquid water in any considerable amount. Some planets are known to have water ice or atmospheric water vapor; some moons of Saturn and Jupiter (which are not planets) show evidence of having sub-surface oceans of liquid water owing to tidal heating effects; other planets including Mars and Venus (both of which were thought to have significant amounts of surface water in their history) continue to be studied for the possibility of liquid water below the surface.
earth is the only planet known to house liquid water and life
Sure There are planets in our solar system that have 100% liquid surfaces, why not water.
Earth is just the right distance from the sun, receiving just enough energy to allow liquid water to exist on the planets surface. If earth were a little further away, then the water would be frozen as ice, while much closer and the water would boil away as water vapour. Liquid water is essential for allowing life to exist.
Earth is the only planet in our solar system with an abundance of liquid water on its surface. Other planets may have water in the form of ice or vapor, but not in liquid form like Earth.
Liquid water is an indicator that there is probably life present.
The earth is in what astronomers call the 'Goldylocks Zone': Just the right distance from our sun that liquid water can exist.