Nidaba (crater)

This article is about the crater. For the Sumerian goddess, see Nisaba.
Nidaba
An image of Nidaba, taken by Voyager 2 on 9 July 1979.
Feature typePenepalimpsest[1]
Coordinates17°45′N 123°26′W / 17.75°N 123.43°W / 17.75; -123.43
Diameter199 kilometres (124 mi)[2]
EponymNidaba

Nidaba is a penepalimpsest,[1][3] an ancient crater in the process of disappearing, on Ganymede, the largest moon of the planet Jupiter. The penepalimpsest is approximately 199 kilometres (124 mi) wide, and a smaller, younger, and better-preserved crater lies within it.[2]

Naming

Nidaba is named after the Sumerian goddess of grains, cereals, and reeds, Nidaba (or Nisaba). As reeds were once used as writing tools, she was also associated with accounting and writing.[4]

Nidaba's name follows the naming convention established by the IAU, which specifies that craters on Ganymede should be named after deities, heroes, or places from Ancient Middle Eastern mythology. Sumerian mythology traditionally falls within this category.[5]

The IAU approved the name for Nidaba in 1985.[2]

Location

Nidaba is located in the southwestern section of the dark, ancient region on Ganymede known as Galileo Regio. The area around Nidaba is densely packed with craters, palimpsests (or ghost craters), and other possible penepalimpsests, reflecting the region's ancientness.[3]

To the west of Nidaba is the wide palimpsest Memphis Facula and one of the most well-studied ghost craters in the Solar System. To the east lies the bright-floor crater Selket, while to the southwest is the more well-preserved pit crater Ninlil.[3]

Nidaba is located within the Memphis Facula quadrangle of Ganymede (designated Jg7), which is named after the ghost crater near Nidaba.[6]

Nidaba is situated on the hemisphere of Ganymede that never faces Jupiter. This is because the moon is synchronously rotating as it orbits around its parent planet. Therefore, if an observer were to stand on Nidiba, they would never see Jupiter in the sky.[a]

Age and geology

Nidiba is often called a penepalimpsest,[1] an ancient crater that is on the verge of becoming a palimpsest (or ghost crater) and ultimately disappearing. The distinction between palimpsests and penepalimpsests is not always well defined, and the two are sometimes classified as the same type of structure. As a penepalimpsest, Nidiba still displays more well-defined and well-developed concentric ridges and hills than its more ghostly palimpsest counterparts, such as Memphis Facula and Buto Facula.[3][8]

Within Nidaba is a more recent, better-preserved pit crater, but it has not yet received a formal name.

Process of Crater Erasure

It is generally believed that there are two main reasons why craters on Ganymede tend to disappear over time. The first is Ganymede's relatively slow tectonic activity, which gradually erodes and erases surface craters. As fresh water ice erupts from beneath Ganymede's surface, it overprints older terrain and obscures ancient surface features, including dark regions such as Galileo Regio and older impact craters such as Nidiba.[9][10]

The second process believed to erase craters is viscous relaxation. Because Ganymede's surface is composed largely of ice, it slowly flows over time, causing crater floors to rise isostatically while crater rims slump. Eventually, a crater may become barely visible — like in the case of the crater Zakar — before disappearing entirely.[11]

The majority of viscously relaxed craters are found within Ganymede's dark terrain, and Nidaba may be one of them.[11]

Exploration

During its July 1979 flyby, Voyager 2 became the first spacecraft to image the side of Ganymede that never faces Jupiter. During its closest approach, the probe successfully captured images of Galileo Regio and Nidaba.[12]

Galileo was the next—and, as of 2026, the last—spacecraft to explore and image Nidaba. It did so while orbiting Jupiter from December 1995 to September 2003. Galileo obtained medium-resolution images of Nidaba; however, during its close flyby of Galileo Regio in June 1996, the spacecraft focused its camera on the nearby Memphis Facula instead. As a result, Nidaba was not imaged at high resolution.[3][13]

Future missions

The European Space Agency's (ESA) Jupiter Icy Moons Explorer (Juice) is scheduled to arrive at Jupiter in July 2031.[14] After conducting multiple flybys of Europa, Ganymede, and Callisto during approximately three and a half years in orbit around Jupiter, Juice will enter a low orbit around Ganymede in July 2034, at an altitude of about 500 kilometres (310 mi).[15] The probe is expected to return high-resolution images of Nidaba which Galileo missed.

See also

Notes

  1. ^ For moons in synchronous rotation, such as Ganymede, 0° longitude corresponds to the part of the surface that always faces Jupiter. Regions between 90° W and 270° W longitude never face the moon's parent planet.[7]

References

  1. ^ a b c Jones, Kevin; Head, James III; Pappalardo, Robert; Moore, Jeffrey (July 2003). "Morphology and origin of palimpsests on Ganymede based on Galileo observations". Icarus. 164 (1): 198. Retrieved 2026-01-27.
  2. ^ a b c "GANYMEDE - Nidaba". USGS. 2015. Retrieved 2026-01-27.
  3. ^ a b c d e Schenk, Paul, ed. (2012). Atlas of the Galilean Satellites. Cambridge University Press. pp. 136, 137. doi:10.1017/CBO9780511676468. ISBN 9780511676468.
  4. ^ "Nissiba Assyrian deity". Britannica. 2026. Retrieved 2026-01-27.
  5. ^ "Categories (Themes) for Naming Features on Planets and Satellites". USGS. 2026. Retrieved 2026-01-27.
  6. ^ Ganymede Map Images Archived 2007-11-19 at the Wayback Machine
  7. ^ "Discussion of Chapter 6". Open University. Retrieved 2026-01-27.
  8. ^ Moore, Jeffrey; White, Oliver; Korycansky, Donald; Schenk, Paul; Dombard, Andrew; Caussi, Martina (2024-08-04). "Buto Facula, Ganymede: Palimpsest Exemplar". not mentioned: 1, 2, 3, 4, 5, 6. Retrieved 2026-01-27.
  9. ^ "Geology and mapping of dark terrain on Ganymede and implications for grooved terrain formation". NASA. 2000. Retrieved 2026-01-27.
  10. ^ "Ganymede: Bright and Dark Terrain". AGU Publications. 2000. Retrieved 2026-01-27.
  11. ^ a b Bland, Michael; Singer, Kelsi; McKinnon, William; Schenk, Paul (2017-11-01). "Viscous relaxation of Ganymede's impact craters: Constraints on heat flux". Icarus. 296: 275, 276, 285, 286. Retrieved 2026-01-27.
  12. ^ "Eyes in the Solar System". NASA. 2026. Retrieved 2026-01-27.
  13. ^ "Juice Jupiter Icy Moons Explorer". The Planetary Society. 1996. Retrieved 2026-01-27.
  14. ^ "Juice Jupiter Icy Moons Explorer". ESA. 2023. Retrieved 2026-01-27.
  15. ^ "Juice's journey and Jupiter system tour". ESA. 2022. Retrieved 2026-01-27.
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