New analysis of Cassini data yields insights into Titan’s seas

A new study of data from the Cassini-Huygens radar experiment has provided new insights into the composition and activity of a liquid hydrocarbon ocean near the north pole of Titan, the largest of Saturn’s 146 known moons.

Using data from multiple bistatic radar experiments, the Cornell-led research team was able to independently analyze and estimate the composition and roughness of Titan’s ocean surface, something that previous analyses of monostatic radar data could not achieve. This paves the way for future comprehensive investigations of the nature of Titan’s ocean using Cassini data.

Valerio Poggiali, a research scientist at Cornell University, is lead author of the report, “Surface Properties of Titan’s Mare Revealed by the Cassini Mission’s Bistatic Radar Experiment,” published July 16. Nature Communications.

A bistatic radar experiment involves directing a radio beam from a spacecraft to a target (in this case Titan), where the beam is reflected to a receiving antenna on Earth. This surface reflection is polarized and provides information gathered from two independent perspectives, as opposed to monostatic radar data, where the reflected signal is returned to the spacecraft.

“The main difference is that bistatic information is a more complete data set and is sensitive to both the composition of the reflective surface and its roughness,” Poggiali said.

In this study, four bistatic radar The research team analyzed Titan’s surface reflectivity based on observational data collected by Cassini during four flybys on May 17, June 18, October 24, 2014, and November 14, 2016. During each flyby, surface reflectivity was observed when the spacecraft was closest to Titan (approach) and when it was moving away (exit). The research team analyzed the exit observation data from Titan’s three large polar oceans: Kraken Mare, Ligeia Mare, and Punga Mare.

Their analysis found that the composition of the hydrocarbon ocean’s surface layers varies by latitude and location (for example, near rivers and estuaries). Specifically, the southernmost parts of Kraken Mare have the highest dielectric constant, a measure of a material’s ability to reflect radio signals. Earth’s water, for example, is highly reflective, with a dielectric constant of about 80, while Titan’s ethane and methane oceans have a dielectric constant of about 1.7.

The researchers also noted that all three areas were largely calm at the time of the flyby. surface Waves below 3.3 mm. Slightly higher levels of roughness (up to 5.2 mm) Coastal areassigns of estuaries, straits and tides are seen.

“There’s also evidence that the rivers that feed the oceans are pure methane until they flow into the open ocean, which is liquid and rich in ethane,” Poggiali said, “just as freshwater rivers on Earth flow into the salty oceans and mix with them.”

“This is in good agreement with weather models of Titan,” said co-author Philip Nicholson, a professor of astronomy, “which predict that the ‘rain’ falling from Titan’s skies is almost pure methane, with traces of ethane and other hydrocarbons.”

Poggiali said further study is already being done on the data Cassini has collected during its 13 years of studying Titan. “There is a whole lot of data waiting to be fully analyzed in a way that will lead to further discoveries,” he said. “This is just the first step.”

The research also involves collaborators from the University of Bologna, the Paris Observatory, NASA’s Jet Propulsion Laboratory (JPL), California Institute of Technology, and Massachusetts Institute of Technology.