Aztlan Is Equatorial Dark Albedo Feature on Titan's Saturn-Facing Side

Summary: Aztlan is an equatorial dark albedo feature on Titan's Saturn-facing side that forms a low albedo quartet with Aaru, Fensal and Senkyo.

Annotated mosaic of Aztlan-Fensal's dark, sidewise letter h is composed of 20 images, at near-infrared wavelengths, obtained Sep. 7, 2005, by Cassini spacecraft's Narrow-Angle Camera (NAC); mosaic is centered at 6.5 degrees north latitude, 20.6 degrees west longitude; image addition date 2005-11-04; image credit NASA/JPL/Space Science Institute: May be used for any purpose without prior permission, via NASA JPL Photojournal

Aztlan is an equatorial dark albedo feature on Titan's Saturn-facing side that forms an equatorial quartet of low albedo, or low reflectance, with three optically dark neighbor, Aaru, Fensal and Senkyo.

Aztlan is centered at minus 10 degrees south latitude, 20 degrees west longitude, according to the International Astronomical Union's (IAU) Gazetteer of Planetary Nomenclature. The Gazetteer assigns the low albedo feature's center latitude of minus 10 degrees south as its northernmost and southernmost latitudes and its center longitude of 20 degrees west as its easternmost and westernmost longitudes.

The southern equatorial-centered dark albedo feature participates with a trio of low albedo neighbors in forming an optically dark quartet in Titan's equatorial belt. Aztlan joins southern equatorial-centered Senkyo and northern equatorial-centered Aaru and Fensal in a darkened stretch across Titan's meridian.

Aztlan partners with Fensal as the dark quartet's low western longitudinal components. Fensal is positioned to the north of Aztlan.

Fensal is centered at 5 degrees north latitude, 30 degrees west longitude. The center coordinates of 5 degrees north and 30 degrees west are given as the low reflector's northernmost-southernmost latitudes and easternmost-westernmost longitudes, respectively.

Aaru partners with Senkyo as the dark quartet's far western longitudinal components. Aaru is positioned to the north of Senkyo.

Aaru is centered at 10 degrees north latitude, 340 degrees west longitude. Its center coordinates are also given as the low reflector's northernmost-southernmost latitudes and easternmost-western longitudes.

Senkyo is centered at minus 5 degrees south latitude, 320 degrees west longitudes. Its center latitude and longitude are also repeated as its northernmost-southernmost latitudes and easternmost-westernmost longitudes.

A pareidolia (Greek: παρά, pará, "beside, alongside, instead [of]" plus εἴδωλον, eídōlon, "image, form, shape") distinguishes the Titanean equatorial belt's quartet for Earth-based observers. Aztlan's and Fensal's parallel darkness appears as a sidewise lowercase letter h. Fensal forms the northern leg of the pareidolia, while Aztlan contributes the optical illusion's southern leg. Prior to official naming, the region of the two features was known as "the H," according to NASA Jet Propulsion Laboratory's (JPL) Photojournal website's post, "Monitoring 'Fensal-Aztlan,'" published Sep. 13, 2005.

Landforms described as "islands" occur in the Aztlan-Fensal neighborhood. The "islands" are considered to be water ice upland areas that outcrop the surrounding shallow terrain of dark particulate infill. The islands, which are mainly small but with a few larger exceptions, pepper Fensal.

Aztlan's scarcity of the insular landforms contrasts with neighbor Fensal's insular abundance. The September 2005 post notes Aztlan's comparative devoidness of small insular landforms in an inventory of "three large islands in its western reaches, plus only a few smaller islands."

Sotra Facula is identified as the largest of Aztlan's three large islands. Sotra Facula (Latin: "little torch") received official name approval in 2006 but was subsequently dropped from Titan's list of facula and approved in 2012 as Sotra Patera (Latin: patera, "small, broad, flat dish or saucer, usually used for ritual libations"), according to The Gazetter of Planetary Nomenclature.

Sotra Patera is centered at minus 14.54 degrees south latitude, 40 degrees west longitude. It records northernmost and southernmost latitudes of minus 14.18 degrees south and minus 14.98 degrees south, respectively. It registers easternmost and westernmost longitudes of 39.74 degrees west and 40.46 degrees west, respectively. Sotra Patera's diameter measures 40 kilometers.

The dark quartet created by the neighboring duos of Aztlan-Fensal and Aaru-Senkyo occupies the extensive dune fields that occur in Titan's equatorial belt. A preferential detection of acetylene (C2H2) occurs in low albedo areas, such as sand dunes, according to planetary scientist Sandeep Singh and eight co-authors in their article, "Acetylene on Titan's Surface," published in the Sep. 1, 2016, issue of The Astrophysical Journal. Their study focused on three equatorial regions of Aztlan-Fensal and their shared, high albedo, equator-centered neighbor, Quivira; Tui Regio; and eastern Shangri-La. Their dectection of strong absorption bands of acetylene in Aztlan-Fensal's dark dunes confirmed their prediction of the presence of acetylene in dark-composed dune fields.

The International Astronomical Union approved Aztlan's name in 2006. The Gazetteer of Planetary Nomenclature identifies Aztlan as: "Mythical land from which the Aztecs believed they migrated." The name conforms with the IAU convention of naming Titan's albedo features for "Sacred or enchanted places, paradise, or celestial realms" as identified in "legends, myths, stories, and poems of cultures from around the world."

Image, acquired April 13, 2013, by Cassini spacecraft's Narrow-Angle Camera (NAC), with 938 nanometer-centered, near-infrared wavelength sensitive spectral filter, shows the dark quartet of Aztlan and Fensal (left) and Aaru and Senkyo (right); image obtained at approximate distance of 1.117 million miles (1.797 million kilometers) from Titan and at Sun-Titan-spacecraft, or phase, angle of 4 degrees; image addition date 2013-06-03; image credit NASA/JPL-Caltech/Space Science Institute: No known coyright restrictions, via NASA Image and Video Library

Acknowledgment

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

Dedication

This post is dedicated to the memory of our beloved blue-eyed brother, Charles, who guided the creation of the Met Opera and Astronomy posts on Earth and Space News. We memorialized our brother in "Our Beloved Blue-Eyed Brother, Charles, With Whom We Are Well Pleased," published on Earth and Space News on Thursday, Nov. 18, 2021, an anniversary of our beloved father's death.

Image credits:

Annotated mosaic of Aztlan-Fensal's dark, sidewise letter h is composed of 20 images, at near-infrared wavelengths, obtained Sep. 7, 2005, by Cassini spacecraft's Narrow-Angle Camera (NAC); mosaic is centered at 6.5 degrees north latitude, 20.6 degrees west longitude; image addition date 2005-11-04; image credit NASA/JPL/Space Science Institute: May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA07753

Image, acquired April 13, 2013, by Cassini spacecraft's Narrow-Angle Camera (NAC), with 938 nanometer-centered, near-infrared wavelength sensitive spectral filter, shows the dark quartet of Aztlan and Fensal (left) and Aaru and Senkyo (right); image obtained at approximate distance of 1.117 million miles (1.797 million kilometers) from Titan and at Sun-Titan-spacecraft, or phase, angle of 4 degrees; image addition date 2013-06-03; image credit NASA/JPL-Caltech/Space Science Institute: No known copyright restrictions, via NASA Image and Video Library @ https://images.nasa.gov/details-PIA14663; May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA14663

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