Ů��С��Ƶ

Slowly but surely, the surface of Saturn’s strange moon Titan is being revealed. Researchers have made the first map of the geology of Titan’s entire surface, and it will eventually help us figure out what the climate is like there.

Titan’s atmosphere is full of a thick, orange haze that blocks visible light from reaching the surface, making it difficult for spacecraft to take pictures. NASA’s Cassini spacecraft, which orbited Saturn from 2004 to 2017, took radar and infrared data of Titan’s surface, giving researchers a hint of the terrain below.

Rosaly Lopes at NASA’s Jet Propulsion Laboratory in California and her colleagues assembled those observations and placed each area, or unit, into one of six categories: lakes, craters, dunes, plains, hummocky terrain – meaning hills and mountains – and labyrinth, which looks like heavily eroded plateaus. They then made a map of where each of those terrains exists on Titan’s surface.

They found that the landscape type depended strongly on the latitude. The equator is mostly covered in dunes, with flatter plains dominating the mid-latitudes and lakes and labyrinths closer to the poles. “The surprise is how clear the latitudinal distribution is,” says Lopes. “We had seen some of that already but by doing a global map it really stands out.”

By looking at how the different terrains were layered, they also determined that the oldest areas on the surface are probably the mountains, which are bits of the moon’s icy crust.

The youngest are the lakes and dunes. Sand from the dunes seems to be blowing over the plains, creating a fuzzy border between the two zones, but because of the difficulty of taking pictures of Titan we don’t yet have a good handle on many of the geological processes shaping the landscape.

“Now that we have this global picture, we need to start to correlate these units with climate models to find out how the rain and wind are behaving, how the landscape is evolving,” says Lopes.