Abstract

Abstract We present Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of sun glitter—wave-induced reflections from a liquid surface offset from a specular point—on Kraken Mare. Sun glitter reveals rough sea surfaces around Kraken Mare, namely the coasts and narrow straits. The sun glitter observations indicate wave activity driven by the winds and tidal currents in Kraken Mare during northern summer. T104 Cassini VIMS observations show three sun glitter features in Bayta Fretum indicative of variegated wave fields. We cannot uniquely determine one source for the coastal Bayta waves, but we lean toward the interpretation of surface winds, because tidal currents should be too weak to generate capillary–gravity waves in Bayta Fretum. T105 and T110 observations reveal wave fields in the straits of Seldon Fretum, Lulworth Sinus, and Tunu Sinus that likely originate from the constriction of tidal currents. Coastlines of Bermoothes and Hufaidh Insulae adjoin rough sea surfaces, suggesting a complex interplay of wind-roughened seas and localized tidal currents. Bermoothes and Hufaidh Insulae may share characteristics of either the Torres Strait off Australia or the Åland region of Finland, summarized as an island-dense strait with shallow bathymetry that hosts complex surface circulation patterns. Hufaidh Insulae could host seafloor bedforms formed by tidal currents with an abundant sediment supply, similar to the Torres Strait. The coastlines of Hufaidh and Bermoothes Insulae likely host ria or flooded coastal inlets, suggesting that the Insulae may be local peaks of primordial crust isolated by an episode of sea-level rise or tectonic uplift.

Highlights

  • The Cassini mission peered through Titan’s hazy veil, discovering isolated liquid bodies on its surface (Stofan et al 2007)

  • Cassini Visual and Infrared Mapping Spectrometer (VIMS) collected hundreds of 32×1 “noodle” cubes during the T104 flyby that scanned over the entire Bayta Fretum region at a sampling of 7 km/pixel and were reconstructed with the steps outlined in Barnes et al (2008)

  • We note that the T104 and T110 Bayta observations from Figure 9 were recorded at the same true anomaly, indicating diurnal tides may not be responsible for the sun glitter

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Summary

INTRODUCTION

The Cassini mission peered through Titan’s hazy veil, discovering isolated liquid bodies on its surface (Stofan et al 2007). The hydrological cycle of liquid methane is active in the presence of these vast hydrocarbon seas, including the seasonal evolution of wind and Figure 1 This cartoon illustrates the observation geometry of a specular reflection (sunlight directly reflected off a planetary surface) and sun glitter (waves tilting the liquid surface toward an observer, like Cassini VIMS) off a dark Titan sea surface in the left and right diagrams respectively. We quantify the sea surface roughness by the specular deviation angle (θ in Figure 1), which describes the angle at which the liquid surface needs to be tilted toward an observer to achieve a specular reflection. For Titan, the Visual and Infrared Mapping Spectrometer (VIMS) (Brown et al 2004) observes solar specular reflections as bright or possibly saturated pixels in the atmospheric windows used for the color image.

MODERATE-SAMPLING SUN GLITTER OBSERVATIONS
SPECTRAL ANALYSIS
FINE-SAMPLING SUN GLITTER OBSERVATIONS
Bayta Fretum
Tunu Sinus
DISCUSSION
Tidal Currents
Surface waves
Coastal Morphology of Hufaidh and Bermoothes Insulae
Origin of T110 Tunu Sinus sun glitter
CONCLUSION
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