We Thought Titan’s Hydrocarbon Seas Were Absolutely Tame. Not Quite

In its orography, Titan, Saturn's largest moon, is one of the most Earth-like places in the solar system. This similarity is due to its rivers, lakes and unique “water cycle.” The main difference is that various hydrocarbons play the role of water on Titan.

Waves and currents. But these organic compounds have significant parallels to water on Earth, parallels that experts are still discovering. A recent study published in Nature Communications of data collected by the Cassini-Huygens mission has revealed that these hydrocarbon seas have their own (tiny) waves and, more importantly, ocean currents.

Hydrocarbon sea. Since the Cassini-Huygens mission revealed the existence of these hydrocarbon seas, analysis of Titan’s surface and atmosphere has allowed experts to create climate models that show this hydrocarbon “water cycle.”

According to these models, Titan’s rain is composed of methane. This methane falls to the surface and flows through rivers to the large hydrocarbon seas. The new study analyzes the three major seas in Titan’s polar zone: Kraken Mare, Ligeia Mare, and Punga Mare.

Extremely tame. By analyzing these seas, the team learned more about their hardness and composition. Titan’s seas are unimaginably tame, so much so that until now, researchers have detected their tiny waves, with tides barely exceeding half a centimeter.

Specifically, the team detected swells of up to 3.3 millimeters in these seas. However, these waves could reach up to 5.2 millimeters in coastal areas. The team explains that this indicates the presence of tidal currents.

Varying compositions. The team also found evidence that the composition of these rivers, seas, and estuaries varies with latitude and the type of environment where they reside.

For example, they found evidence that the rivers are composed of methane. This finding supports climate models we have of Titan, which suggest that its rainfall would consist almost entirely of liquid methane. At the same time, its oceans would be rich in ethane.

The study’s authors compare these findings to the water cycle on Earth. Here, rain is fresh water flowing through rivers and dominates until it reaches the ocean, where it mixes with salt water.

The Cassini-Huygens radar. Although the team recently published the study’s results, they used the data collected by the now-retired Cassini-Huygens mission between 2014 and 2016. The team used measurements from the spacecraft’s radar, but they took advantage of some unique measurements obtained using the bi-static radar experiments, as opposed to those previously used, which were based on monostatic radar.

The difference is in who receives the radar signal. With monostatic radar, the spacecraft emits the radio signal and receives it when it returns. With bistatic radar, antennas on Earth receive the signal emitted by Cassini and bounce off Titan’s surface.

According to the team behind the research, these findings have created a “more complete” database. 

Titan’s “icebergs.” Recently, researchers published new data on another feature of Titan’s seas, the so-called “magic islands.” These islands would be more like “icebergs” formed by organic compounds present in these hydrocarbon seas, which form and dissolve in Titan’s “waters.”

Dragonfly mission. We’ve learned all of this because of the data collected by a mission that ended about seven years ago. The team in charge of that mission has highlighted the wealth of information about Saturn’s largest satellite, which still hides many mysteries. This study is the “first step” in uncovering this hidden information.

The ambitious Dragonfly mission will complement this info in a few years, which aims to place a new probe on this satellite. It's ambitious because this probe will take the form of a drone capable of taking off and moving through Titan’s atmosphere.

This article was written by Pablo Martínez-Juarez and originally published in Spanish on Xataka.

Image | NASA/JPL-Caltech/ASI/USGS | Steven Hobbs

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