The Bathymetry of Moray Sinus at Titan's Kraken Mare. Issue 12 (4th December 2020)

• Record Type: Journal Article
• Authors: Poggiali, V.; Hayes, A. G.; Mastrogiuseppe, M.; Le Gall, A.; Lalich, D.; Gómez‐Leal, I.; Lunine, J. I.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 12(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-12-04
• Subjects: Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1029/2020JE006558
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: Moray Sinus is an estuary located at the northern end of Titan's Kraken Mare. The Cassini RADAR altimeter acquired three segments over this mare during the T104 flyby of Titan, on August 21, 2014. Herein, we present a detailed analysis of the received echoes. Some of these waveforms exhibit a reflection from the seafloor, from up to 85 − 18 + 28 m of depth (1 σ error). Monte Carlo simulations have been performed in order to assess the most probable values and estimation errors for the seafloor depth. Insights from this study, featuring the synergic use of the synthetic aperture radar images coupled to the altimetry and passive radiometry datasets, have been used to constrain the dielectric properties (i.e., absorptivity of the liquid) and roughness of this region of Kraken Mare. The resulting Ku‐band specific attenuation of the liquid is 17 − 3 + 3 dB/μs, corresponding to a loss tangent of 4.6 − 0.9 + 0.9 × 10 − 5, which is very similar to the loss tangent estimated at Ligeia Mare. The data in hand do not permit us to discern the most likely explanation for the lack of a seafloor reflection from the main body of Kraken Mare: either a very deep sea or a more absorbing liquid composition. However, if the main body of Kraken Mare is characterized by an absorption similar to Moray Sinus, then based on models of the response to altimetry mode observations we can conclude that it exceeds 100 m of depth, which is also compatible with radiometry observations. Plain Language Summary: From 2013 to 2017, we have been probing the depth of Titan's methane‐dominated seas by penetrating the liquid with Cassini's radar altimeter. The depth and composition of each of the seas had already been derived, except for Titan's largest sea Kraken Mare. Herein, we describe the final observation of this campaign before the end of Cassini in 2017. Our analysis reveals that the seafloor at the center of Moray Sinus—an estuary located at the northern end of Kraken Mare, is up to 85 m deep. The radar waves are absorbed to an extent such that the liquid composition is compatible with 70% methane, 16% nitrogen, and 14% ethane (assuming ideal mixing). The analysis of the altimetry data in the main body of Kraken Mare showed no evidence for signal returns from the sea floor, suggesting the liquid is either too deep or too absorptive for Cassini's radio waves to penetrate. However, if the liquid in the main body of Kraken Mare is similar in composition to Moray Sinus, as one would expect, then its depth exceeds 100 m. This is compatible with a separate estimate using the radar as a "radiometer, " sensing thermal energy from the sea at radio wavelengths. Key Points: Moray Sinus is an estuary located at the northern end of Titan's Kraken Mare Analysis of Cassini's radar altimeter data shows that the near‐shore local seafloor is up to 85 m deep in Moray Sinus estuary The composition of the sea, inferred from radar absorptivity, is very similar to that estimated at Ligeia Mare The main body of Kraken Mare exceeds 100 m of depth