Currently, Earth is the only known planet (or moon) to have consistent, stable bodies of liquid water on its surface. In our solar system, Earth orbits around the sun in an area called the habitable zone. The temperature, along with an ample amount of atmospheric pressure within this zone, allows water to be liquid for long periods of time. There is growing evidence suggesting that the planet Mars has subsurface liquid water, but this is yet to be confirmed. Other than Earth, Europa (one of Jupiter’s fifty known moons) is the only celestial body in our solar system with evidence suggesting there is an ocean.
Original article: Are there oceans on other planets?