Saturn’s largest moon Titan has always fascinated astronomists because of its similarity to Earth. Many even considered the notion that life could be possible on it. Very recently the Cassini mission ended which collected a humongous amount of data on Saturn and it’s moon Titan. Now, a new study based on this data claims that the geology of Titan is very similar to that of our Earth.
A decade ago, we knew very little about Titan other than its size and that it had a dense, nitrogen-rich atmosphere. Now, after the Cassini mission, data revealed the presence of lakes and seas of liquid methane and ethane, replenished by rain from hydrocarbon clouds. There is also evidence for an internal, liquid ocean 35 to 50 miles (55 to 80 kilometres) beneath its surface, likely composed of water and ammonia.
Now, there is also a new map that combines data from all the sources available. Since only about 9 percent of Titan has been observed in relatively high-resolution topography, with 25-30 percent of the topography imaged in lower resolution, the remainder of the moon was mapped using an interpolation algorithm and a global minimisation process, which reduced errors such as those arising from spacecraft location. The map revealed new mountains, none higher than 700 meters and a global view of the highs and lows of Titan’s topography, which enabled the scientists to confirm that two locations in the equatorial region of Titan are in fact depressions that could be ancient, dried seas or cryo-volcanic flows.
The map also revealed that Titan is a little bit flatter, more oblate than was previously known, which suggests there is more variability in the thickness of Titan’s crust than previously thought.
This research also raises a new mystery for Titan. A vast majority of Titan’s lakes sit in sharp-edged depressions. The lakes are surrounded by high ridges, hundreds of meters high in some places. They seem to be formed the way karst is on Earth, in places like the Florida Everglades, where underlying material dissolves and the surface collapses, forming holes in the ground. The lakes on Titan, like Earth’s karst, are topographically closed, with no inflow or outflow channels. But Earth karst does not have sharp, raised rims.
The shape of the lakes indicates a process called uniform scarp retreat, where the borders of the lakes are expanding by a constant amount each time. The largest lake in the south, for example, looks like a series of smaller empty lakes that have coalesced or conglomerated into one big feature.
- A. G. Hayes Jr, et al. Topographic constraints on the evolution and connectivity of Titan’s lacustrine basins. AGU Fall Meeting Abstracts (2015).
- A. G. Hayes Jr, et al. Topographic Constraints on the Evolution and Connectivity of Titan’s Lacustrine Basins. Geophysical Research Letters. 44 (23): 11,755 (2017). 10.1002/2017GL075518
- P. Corlies et al., Titan’s Topography and Shape at the End of the Cassini Mission. 44 (23): 11,754 (2017) 10.1002/2017GL075468