Kraken Mare, a sea of liquid methane on Saturn’s moon Titan, is at least 100-m (330 feet) deep near its center, according to an analysis of data collected by the RADAR altimeter onboard NASA’s Cassini spacecraft on August 21, 2014.
An artistic rendering of Kraken Mare, a large liquid methane sea on Titan. Image credit: NASA’s John Glenn Research Center.
From 2013 to 2017, Cassini has been probing the depth of Titan’s methane-dominated seas by penetrating the liquid with its altimeter.
The depth and composition of each of the seas had already been derived, except for Titan’s largest sea Kraken Mare.
“The depth and composition of each of Titan’s seas had already been measured, except for Titan’s largest sea, Kraken Mare, which not only has a great name, but also contains about 80% of the moon’s surface liquids,” said Dr. Valerio Poggiali, a researcher in the Cornell Center for Astrophysics and Planetary Science at Cornell University.
In 2014, Cassini’s RADAR instrument measured the liquid depth at Moray Sinus, an estuary located at the northern end of Kraken Mare.
Dr. Poggiali and colleagues had figured out how to discern lake and sea bathymetry (depth) by noting the radar’s return time differences on the liquid surface and sea bottom, as well as the sea’s composition by acknowledging the amount of radar energy absorbed during transit through the liquid.
It turns out that Moray Sinus is about 85 m (280 feet) deep, shallower than the depths of central Kraken Mare, which was too deep for the radar to measure.
Surprisingly the liquid’s composition, primarily a mixture of ethane and methane, was methane-dominated and similar to the composition of nearby Ligeia Mare, Titan’s second-largest sea.
The observation is an important finding that will help in assessing models of Titan’s Earth-like hydrologic system.
This image of Titan, taken by Cassini spacecraft, reveals differences in the composition of surface materials around hydrocarbon lakes and seas on this largest moon of Saturn. Image credit: NASA / JPL-Caltech / University of Arizona / University of Idaho.
“Titan represents a model environment of a possible atmosphere of early Earth,” Dr. Poggiali said.
“Thanks to our measurements, scientists can now infer the density of the liquid with higher precision, and consequently better calibrate the sonar aboard the vessel and understand the sea’s directional flows.”
“One puzzle is the origin of the liquid methane,” he added.
“Titan’s solar light — about 100 times less intense than on Earth — constantly converts methane in the atmosphere into ethane; over roughly 10 million-year periods, this process would completely deplete Titan’s surface stores.”
“In the distant future, a submarine — likely without a mechanical engine — will visit and cruise Kraken Mare.”
The team’s results were published in the Journal of Geophysical Research: Planets.
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V. Poggiali et al. The Bathymetry of Moray Sinus at Titan’s Kraken Mare. Journal of Geophysical Research: Planets, published online November 12, 2020; doi: 10.1029/2020JE006558
