The surfaces of both Earth and Mars show extensive evidence of liquid water although the evidence on Mars dates back to well over 3 billion years ago. Plate tectonics seems to play a symbiotic role with a planet’s liquid water. If one disappears, so does the other. In the solar system, Earth is uniquely suited for vibrant, long-standing plate tectonics and abundant liquid oceans. Check out this previous TNRTB post to see why this life-essential plate-tectonics/large-ocean combination is rare.