Tsegihi Is Mid-Latitude Bright Albedo Feature on Titan's Saturn Side

Summary: Tsegihi is a mid-latitude bright albedo feature on Titan's Saturn side that is one of only two albedo features centered outside the equatorial belt.

Titan VIMS (Visible and Infrared Mapping Spectrometer) image shows southern mid-latitude-centered bright albedo feature Tsegihi (center right) with northwestern bright albedo feature Xanadu (upper left) on Titan's Saturn-facing side: map credit NASA/JPL/University of Airzona, via IAU/USGS Astrogeology Science Center Gazetteer of Planetary Nomenclature

Tsegihi is a southern mid-latitude bright albedo feature on Titan's Saturn side that occurs as one of only two Titanean albedo features that are not centered on the Saturnian moon's equatorial belt.

Tsegihi is centered at minus 40 degrees south latitude, 10 degrees west longitude, according to the International Astronomical Union’s (IAU) Gazetteer of Planetary Nomenclature. The Gazetteer repeats the bright albedo feature's center coordinates for its northernmost-southernmost latitudes and easternmost-westernmost longitudes.

Tseigihi's southern mid-latitude location qualifies it as one of Titan's only two albedo features that are centered outside the equatorial belt. Tsegihi's southern mid-latitude residence also places the bright albedo feature in proximity to dark Mezzoramia, Titan's other non-equatorial belt-centered albedo feature.

Mezzoramia is centered at minus 70 degrees south latitude, 0 degrees of longitude. Titan's only south polar region albedo feature's center latitude and longitude are given as its northernmost-southernmost latitudes and easternmost-westernmost longitudes, respectively.

Xanadu lies to the northwest of Tsegihi. The highly reflective feature is described as Titan's "largest, brightest region" (5.3.1 Morphology, page 81) by planetary scientist Ralf Jaumann and 10 co-authors in "Geology and Surface Processes on Titan," chapter five of Titan From Cassini-Huygens, published in 2009 under the editorship of Robert H. Brown, Jean-Pierre Lebreton and J. Hunter Waite.

Bright Xanadu is centered at minus 15 degrees south latitude, 100 degrees west longitude. The southern equatorial belt-centered feature records northernmost and southernmost latitudes of 10 degrees north and minus 40 degrees south, respectively. It registers easternmost and westernmost longitudes of 65 degrees west and 150 degrees west, respectively. Xanadu's diameter spans 3,400 kilometers.

High reflectance distinguishes both Tsegihi and Xanadu amid the Titanean surface's extensive patchwork of brightness and darkness, according to University of Arizona Lunar and Planetary Laboratory planetary scientist Jason W. Barnes and 34 co-authors in their report, "A 5-Micron-Bright Spot on Titan: Evidence for Surface Diversity," published in the Oct. 7, 2005, issue of Science. An unusually bright spot, with coordinates of minus 20 degrees south latitude, 80 degrees west longitude, lies to the northwest of Tsegihi and to the southeast of Xanadu.

The Tsegihi-Xanadu neighborhood's bright spot was identified at W.M. Keck Observatory, on Mauna Kea in north central Hawaii ("the Big Island") via the adaptive optics (AO) system's ground-based imaging on the Keck II 10-meter telescope. The Cassini spacecraft's Visual and Infrared Mapping Spectrometer (VIMS) subsequently made consistent observations of the bright spot for nine months, from July 2004 through April 2005.

Spectral comparisons of Tsegihi, the intervening bright spot and Xanadu confirm the lack of sameness in Titan's bright features. Wavelengths shorter than 5 microns (5 μm) find Xanadu exceeding Tsegihi in brightness. Xanadu's registration as dimmer than Tsegihi at 5 microns might suggest that Xanadu may contain more water ice than Tsegihi, as water ice exhibits high absorptivity at 5 microns (pages 94, 95). The bright spot's overall brightness conforms with Xanadu, with the exception of its similarity to Tsegihi in outshining Xanadu at 5 microns. Images created from co-added, 5 micron-wavelength VIMS frames reveal the bright spot's outshining of Tsegihi by 17 percent and of Xanadu by "nearly a factor of 2" (page 94).

Carbon dioxide (CO2) ice generally tracks high reflectivity in the same short-wavelength atmospheric windows as water ice on Titan. Carbon dioxide ice, however, outshines water ice at the 5 micron wavelength. As such, planetary scientist Jason Barnes and his 34 co-authors suggest possible compositions of "eroded layers of CO2 or more recent overlying deposits" (page 95) for Tsegihi and the Tsegihi-Xanadu neighborhood's bright spot.

The International Astronomical Union approved Tsegihi's name in 2006. The Gazetter of Planetary Nomenclature explains Tsegihi as a "Navajo sacred place." According to IAU convention, names for Titan's albedo features are derived from names in the world's cultures for celestial, enchanting, paradisiacal or sacred places.

Detail of Titan With ISS (Imaging Science Subsystem) Background shows bright Tsegihi (center right) with southern albedo feature neighbor dark Mezzoramia (lower right) and northwestern albedo feature neighbor bright Xanadu (upper left): map credit NASA/JPL/Space Science Institute, via IAU/USGS Astrogeology Science Center Gazetteer of Planetary Nomenclature

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Titan VIMS (Visible and Infrared Mapping Spectrometer) image shows southern mid-latitude-centered bright albedo feature Tsegihi (center right) with northwestern bright albedo feature Xanadu (upper left) on Titan's Saturn-facing side: map credit NASA/JPL/University of Airzona, via IAU/USGS Astrogeology Science Center Gazetteer of Planetary Nomenclature @ https://planetarynames.wr.usgs.gov/images/titan_VIMS_comp.pdf

Detail of Titan With ISS (Imaging Science Subsystem) Background shows bright Tsegihi (center right) with southern albedo feature neighbor dark Mezzoramia (lower right) and northwestern albedo feature neighbor bright Xanadu (upper left): map credit NASA/JPL/Space Science Institute, via IAU/USGS Astrogeology Science Center Gazetteer of Planetary Nomenclature @ https://planetarynames.wr.usgs.gov/images/Titan_comp_ISSimage.pdf

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