Khensu (crater)
Dark-floored crater on Ganymede in Uruk Sulcus.
Khensu is an impact crater on Ganymede, the largest moon of Jupiter. It has a dark floor and a bright ejecta blanket, and sits entirely within a grooved terrain region called Uruk Sulcus. The crater is named after the Egyptian god Khensu (also spelled Khonsu), a youthful lunar deity associated with the Moon’s phases and travelers. In New Kingdom mythology, Khensu was the son of Amun-Ra and Mut, worshipped mainly in Thebes. One myth says he gambled with the moon god Thoth, lost, and forfeited much of his moonlight—explaining why the Moon goes through phases and is dimmer than the Sun. The International Astronomical Union approved the name in 1997 (another source says 1999). The IAU’s naming rule for Ganymede craters requires names from deities, heroes, or places in ancient Middle Eastern mythologies, including Egyptian. Another Ganymede crater, Khonsu, refers to the same deity.
Khensu is small, measuring 14.2 kilometers (NASA) or 17 kilometers (USGS) across. It lies entirely within the bright, young Uruk Sulcus. To the north is the dark, ancient terrain Galileo Regio; to the south is the dark region Marius Regio. A few kilometers east is the crater El. Khensu is part of the Uruk quadrangle (Jg8) on Ganymede. It sits on the hemisphere that always faces away from Jupiter due to the moon’s synchronous rotation, so an observer there would never see Jupiter in the sky.
Little is known about Khensu’s formation. The dark interior has no definite explanation. It might be leftover dark material from the impactor. According to Paul Schenk’s *Atlas of the Galilean Satellites*, the crater’s redness and darkness suggest contamination by an unusual impactor. Alternatively, the impactor may have punched through bright surface material to expose a darker subsurface layer. A study by Namitha Baby indicates the dark material came from within Ganymede, excavated from about 1.36 kilometers below the surface. Because of these traits, Khensu is classified as a “dark-floored” or “dark halo” crater, along with others like Kittu and Nergal.
Two spacecraft have photographed Khensu as of 2026. Voyager 2 flew by Ganymede in July 1979, revealing the crater’s dark nature. The Galileo probe flew over Khensu in September 1996, resolving details as small as 111 meters. The next mission to study Ganymede is ESA’s Jupiter Icy Moons Explorer (Juice), arriving at Jupiter in July 2031.
Quick Facts
- Diameter
- 14.2 km 17 km
- Eponym
- Khensu
Facts from the source article.
Lore & Background
Khensu is named after the Egyptian god Khensu (also known as Khonsu), the youthful god of the Moon, lunar phases, and travelers. According to Egyptian mythology during the New Kingdom, he is the son of Amun-Ra and Mut, with worship centered in Thebes. One myth recounts that Khensu gambled with the moon god Thoth and lost, causing him to lose a significant portion of his moonlight, explaining the Moon's phases and reduced brightness. The IAU approved the name for Khensu in 1997 (or 1999, per the article). Another crater on Ganymede called Khonsu shares the same deity.
Khensu is a relatively small crater, 14.2 km (NASA) or 17 km (USGS) across, located entirely within the bright, young Uruk Sulcus. To its north lies the dark, ancient terrain Galileo Regio, and to the south is Marius Regio. A few kilometers east lies the crater El. Khensu lies on the hemisphere of Ganymede that permanently faces away from Jupiter due to synchronous rotation, so an observer there would never see Jupiter.
Little is known about Khensu's formation. The dark floor may be residual material from the impactor, or the impactor may have punched through the bright surface to reveal a darker sublayer. A study by Namitha Baby suggests the dark material came from within Ganymede, excavated from about 1.36 km beneath the surface. Because of its characteristics, Khensu is classified as a 'dark-floored' or 'dark halo' crater, along with Kittu and Nergal.
Reader's Guide
Khensu's significance lies in its classification as a dark-floored or dark halo crater, a type that provides clues about Ganymede's subsurface composition. The article notes two competing explanations for its dark interior: contamination by an unusual impactor, or excavation of a darker sublayer from about 1.36 km depth. This ambiguity underscores the need for further study. The crater was first photographed by Voyager 2 in July 1979, revealing its dark nature, and later by Galileo in September 1996, which resolved details as small as 111 meters. As of 2026, only these two spacecraft have imaged Khensu. The upcoming ESA Juice mission, arriving at Jupiter in July 2031, will enter a low polar orbit around Ganymede at 500 km altitude and is expected to provide clearer images surpassing Galileo's quality. Khensu's location in the Uruk quadrangle and its naming after an Egyptian moon deity reflect the IAU convention for Ganymede craters. Its position on the far side of Ganymede, never seeing Jupiter, adds to its unique context.
Did You Know?
- The crater's diameter is given as 14.2 km by NASA or 17 km by the USGS.
- Only two spacecraft have photographed Khensu: Voyager 2 (1979) and Galileo (1996).
More in Moons of Jupiter, Part 3 1-24
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