These are river networks on Mars, Earth and Titan. From top to bottom, the images span 100km on Mars, 2,000km on Earth and 400km on Titan. The surfaces of Earth, Mars and Titan, Saturn's largest moon, have all been scoured by rivers. Yet despite the Earth-like landscapes of Titan complete with valleys, lakes and mountains, researchers led by City College of New York geologist Benjamin Black have new evidence that the origins of the topography there and on Mars are different from those on Earth, said the college in a statement. Apart from Earth, Titan is the only other planetary body in the solar system with actively flowing rivers, though they are fed by liquid methane instead of water, said the Massachusetts Institute of Technology, whose researchers were also part of the effort. In their paper published in the journal Science, the team identified plate tectonics - the movement of the Earth's crust - on Earth as one key difference. The team discovered that Titan's rivers, likely carved by liquid methane, have not been as thoroughly rerouted as rivers on Earth, and that its topography may grow through processes such as changes in the thickness of the moon's icy crust, due to tides from Saturn. As for arid Mars, the major features of Martian topography formed very early in the history of the planet, influencing the paths of younger river systems, even as volcanic eruptions and asteroid impacts scarred the planet's surface, the researchers said. "It's important to realise that almost every aspect of Earth's surface has been shaped by plate tectonics," Professor Black said. "So there is nowhere we can look to see what landscapes would look like without plate tectonics. That's where Mars and Titan come in. We can use these three worlds as natural experiments. They are like siblings that have followed different life paths."