Abstract
In this thesis, I investigate the occurrence of sun glitter and waves on the sea surfacesof Titan’s northern seas, Kraken Mare and Punga Mare. These studies of various sun
glitter features help to uncover unique liquid bodies, such as liquid-filled channels,
better understand the dynamics behind the air-sea-land interactions during the northern summer. Some of these interactions include wind-generated capillary waves, tidal
currents, and wave shoaling.
In Chapter 1, I introduce the physics of sunglint and sun glitter observations in
a terrestrial context and elaborate on the spacecraft geometry that necessitates a sun
glitter observation on Titan. In addition, I provide an overview of prior specular
observations from the seas on Titan and the geographical context for Titan’s seas.
In Chapter 2, I present Cassini 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. I cannot uniquely determine one source for the coastal Bayta waves, but I
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 windroughened 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 the Insulae may be local peaks of primordial crust isolated
by an episode of sea-level rise or tectonic uplift.
In Chapter 3, I present new evidence for active coastal and oceanic features in
Titan’s Punga Mare observed in a high-phase Cassini VIMS observation of sunglint
from the T110 flyby. I observe sunglint in a river, Apanohuaya Flumen, resulting from
differing pixel contributions of land adjacent to the channel and implying smooth
liquid surfaces. Along the eastern coastline, I identify a 5-m-bright margin. A possible
explanation for this brightening may include a coastal margin of rough seas. I find
evidence of variegated sea surface roughness in Fundy Sinus and isolated sun glitter
near Hawaiki Insulae that suggests seasonal interactions between surface winds and
topography. RADAR observations of debouches (where rivers meet bays) within
Punga Mare overlap several bright 5 m pixels that indicate rough liquid surfaces.
We postulate that a change in liquid flow regimes, possibly occurring as surface
streamflow, or bubble outburst events may be responsible for surface roughness near
these debouches. These observations imply air-sea-land interactions and hydrological
activity are present in Titan’s sea district during the northern summer.
In Chapter 4, I summarize the implications of the various sun glitter observations
on Titan oceanography.