Nun Sulci
A chaotic grooved terrain on Ganymede, named after Egyptian chaos.
Nun Sulci is a vast, jumbled region of intersecting grooves on Ganymede, Jupiter’s largest moon. Its surface is crisscrossed in multiple directions, unlike most other sulci on the moon, whose troughs tend to run parallel. The area contains only a few craters, many of which have been warped by the tectonic forces that created the sulci.
The feature is named after Nun, the ancient Egyptian god of the primordial chaos that existed before creation. According to Egyptian myth, the world was once a formless ocean of chaos, personified by Nun, until the sun god Ra emerged from the waters, bringing light and order. The name follows the International Astronomical Union’s convention that Ganymede’s features be named after deities, heroes, or places from ancient Middle Eastern mythologies. The IAU approved the name in 1979.
Nun Sulci lies in Ganymede’s northern mid-latitudes. It is so extensive that, according to official U.S. Geological Survey maps, it covers about 2% of the moon’s surface—though the actual grooved terrain may extend beyond the mapped boundaries. To its west are Perrine Regio, Sicyon Sulcus, and the bright-rayed crater Shu. To the southwest lie the bright-rayed craters Min and Diment, along with Phrygria Sulcus. To the southeast are the bright-rayed craters Ta-urt and Haroeris, as well as the dark, ancient Melotte Regio. To the south is another large, complex feature called Mysia Sulci.
The region has very few impact craters, likely because repeated tectonic activity has resurfaced it. Named craters within Nun Sulci include Asshur and Enlil in the north; Nefertum, Upuant, and Mont near the center; and Zakar, Ammura, and Mor in the south. The sulci occupies most of Ganymede’s fifth quadrangle (designated Jg5), which is named after it.
Geologically, Nun Sulci is a bright, relatively young terrain made of multiple generations of ridges and grooves. It is thought that Ganymede’s bright terrains formed after its dark, rugged ones, created by clear water ice welling up from beneath the crust. This fresh ice reflects sunlight, making the area brighter than surrounding dark regions. Mosaic images show a complex network of light bands trending mostly northwest–southeast or east–west. The craters Nefertum and Zakar were heavily deformed by the tectonic forces that shaped the sulci.
Quick Facts
- Location
- Ganymede, Jupiter
- Length
- 1500 km
- Eponym
- Nun
Facts from the source article.
Lore & Background
Nun Sulci is named after Nun, the Ancient Egyptian personification of the primordial chaos that existed before the world began. According to Egyptian mythology, the world was once an endless ocean of chaos until the sun god Ra emerged, bringing light and order. The name follows the IAU convention that geological features on Ganymede be named after deities, heroes, and places from Ancient Middle Eastern mythology. The IAU approved the name in 1979.
The sulci is located in the northern mid-latitudes of Ganymede and is so extensive that it occupies 2% of the moon's surface according to official USGS maps, though it may be even larger. It is surrounded by numerous features: to the west lie Perrine Regio, Sicyon Sulcus, and the bright ray crater Shu; to the southwest are craters Min and Diment and Phrygria Sulcus; to the southeast are craters Ta-urt and Haroeris and the dark region Melotte Regio; to the south lies Mysia Sulci. Nun Sulci has very few impact craters, likely due to extensive resurfacing by tectonic activity. Named craters within it include Asshur, Enlil, Nefertum, Upuant, Mont, Zakar, Ammura, and Mor.
Geologically, Nun Sulci is a relatively young bright terrain formed by multiple generations of crisscrossing ridges and grooves. It is believed to have formed from clear, fresh water ice upwelling from beneath the crust, which reflects sunlight and makes it bright. The grooves appear to have been created by slip-strike faulting in multiple directions, with two main stages of tectonic deformation: first, northeast–southwest extension with normal faulting, then a counterclockwise rotation of stress to a northwest–southeast extensional regime. This resulted in chaotic grooved terrain where grooves intersect in multiple directions, unlike most other sulci on Ganymede.
Reader's Guide
Nun Sulci is significant as a key example of Ganymede's bright, grooved terrains, which are thought to be younger than the moon's dark, rugged terrains. Its chaotic network of intersecting grooves, formed by multiple episodes of strike-slip faulting, provides insight into the tectonic processes that have shaped Ganymede's surface. The sulci's few craters, such as Nefertum and Zakar, were heavily deformed by these forces, offering evidence of the tectonic history. The bright terrains of Nun Sulci are analogous in age to the dark lunar maria on Earth's Moon, representing the youngest regions of their respective moons. Voyager 1 first captured detailed images of the sulci in 1979, and Galileo later observed a small portion at high resolution in 1997. The European Space Agency's Juice mission, launched in 2023 and arriving at Jupiter in 2031, is expected to complete high-resolution mapping of Nun Sulci that Galileo was unable to capture, furthering understanding of this complex feature.
Did You Know?
- The sulci occupies 2% of Ganymede's surface according to USGS maps, but may be even larger.
- Voyager 1 first clearly viewed Nun Sulci in March 1979, capturing its texture in great detail due to shadows near the terminator.
- The grooves of Nun Sulci were created mostly by slip-strike faulting in multiple directions, unlike most other sulci on Ganymede.
More in Moons of Jupiter, Part 3 1-24
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