Anshar Sulcus

Lore & Background

Anshar Sulcus is named after the ancient Mesopotamian mythological entity Anshar, the primordial personification of the sky who existed before the gods were born. The International Astronomical Union chose this name in 1979, following the convention that surface features on Ganymede should be named after deities, figures, and places from Ancient Middle Eastern mythology. The sulcus begins on the southern side of the midpoint of Masha Sulcus, near a ray crater called Amon, and cuts into Marius Regio from the northwest to the southeast, roughly bisecting the dark region. Halfway along its course, an unnamed ray crater is flanked by two faculae—Buto Facula to the southwest and Hermopolis Facula to the northeast. The sulcus terminates near a crater called Ningishzida, about one-third of the way into Marius Regio. Due to Ganymede's synchronous rotation, the side where Anshar Sulcus is located never faces Jupiter.

Reader's Guide

Anshar Sulcus is significant as an example of Ganymede's bright, young terrain characterized by multiple sets of ridges and grooves. Studies suggest that grooved terrains on Ganymede are created through four tectonic stages, but for Anshar Sulcus specifically, a study by Ianiri, Mitri, Sulcanese, Chiarolanza, and Cioria found that it formed through two stages: first, a right-lateral strike-slip motion split the dark terrain, then crustal spreading occurred as the regions pulled apart, with grooves forming when the newly uplifted crust fractured and tilted. The zones where this young terrain meets the older Marius Regio reveal complex age relationships. The fresh water ice released from beneath Ganymede's crust at Anshar Sulcus reflects sunlight, making it appear brighter than its surroundings. The bright terrains on Ganymede are analogous to the dark lunar maria in terms of age, but are composed of water ice rather than basalt. Three spacecraft—Voyager 1, Voyager 2, and Galileo—have imaged Anshar Sulcus, with Galileo providing the first close-up images of its eastern portion. The European Space Agency's Juice probe, launched in April 2023, is expected to arrive at Jupiter in July 2031 and will eventually settle into a low polar orbit around Ganymede, sending some of the highest-resolution images of Anshar Sulcus.

Did You Know?

• Anshar Sulcus is approximately 1,372 kilometers (853 miles) long.
• It is named after the Mesopotamian sky deity Anshar, who existed before the gods were born.
• The sulcus is located entirely within the dark, ancient region Marius Regio on Ganymede.
• Due to Ganymede's synchronous rotation, an observer on Anshar Sulcus would never see Jupiter.