Titan and Earth share many similar features.
Just as the surface of oceans on Earth lie at what we call ‘sea level,’ Titan’s seas also lie at an average elevation.
It is currently the only other world we know of in our solar system that has stable liquid on its surface.
Smaller lakes on Titan appear at elevations several hundred feet higher than Titan’s sea level. This is similar to lakes found on Earth at high elevation.
For example, the Earth’s highest lake navigable by large ships, Lake Titicaca, is over 12,000 feet [3,700 meters] above sea level.
Titan’s liquid bodies appear to be connected under the surface by something akin to an aquifer system on Earth.
Hydrocarbons seem to be flowing underneath Titan’s surface similar to the way water flows through underground porous rock or gravel on Earth.
This means nearby lakes communicate with each other and share a common liquid level.
Aside from Earth, Titan is the only place in the solar system known to have rivers, rainfall and seas – and possibly even waterfalls.
Of course, in the case of Titan these are liquid methane rather than water on Earth.
Regular Earth-water, H2O, would be frozen solid on Titan where the surface temperature is -180°C (-292°F).
With its thick atmosphere and organic-rich chemistry, Titan resembles a frozen version of Earth several billion years ago, before life began pumping oxygen into our atmosphere.
Because Titan is smaller than Earth, its gravity does not hold onto its gaseous envelope as tightly, so the atmosphere extends 370 miles (595km) into space.
With Titan’s low gravity and dense atmosphere, methane raindrops could grow twice as large as Earth’s raindrops.