Hathor (crater)

Lore & Background

Hathor crater is named after Hathor, a cow-headed goddess from Egyptian mythology who was a popular deity of love, happiness, fertility, festivals, and the sky. The International Astronomical Union chose the name in 1979, following the convention that craters on Ganymede should be named after deities, figures, and places from Ancient Middle Eastern mythology.

Geologically, Hathor is described as a very old multi-ring impact basin. Its transient cavity radius is estimated at ~60 km based on secondary crater scaling, with multiple outer rings indicating significant structural response of the crust. It formed on the grooved terrain Bubastis Sulci, meaning the area was probably already tectonically modified before impact. A study by Thomas, Forni, and Masson argues that the excavation boundary lies at one of the concentric ridges surrounding the center, not at the edge of the smooth central area. They used scaling relationships from lunar craters to estimate the transient cavity radius.

Morphologically, Hathor is an anomalous dome crater resembling others on Ganymede such as Neith and Serapis. According to a study by Dr. White, such craters form when impacts penetrate through cold surface ice into a warm, ductile ice layer below. Dome structures developed when meltwater accumulated beneath the crater, refroze, and caused volumetric expansion that uplifted the center into an icy dome. Dome craters are generally observed only in craters with diameters exceeding ~60 km.

Reader's Guide

Hathor crater's significance lies in its role as a key example of an ancient, highly disrupted impact feature on Ganymede, providing insights into the moon's geological history and thermal evolution. The study by Thomas, Forni, and Masson used Hathor to argue that Ganymede's lithosphere was relatively thin at the time of impact—less than ~12 km thick—and thickened gradually over long periods, contrasting with another study suggesting a thickness of less than 6 km. The multi-ring system of Hathor supports the model that the lithosphere was thinner than the transient cavity depth, leading to multiple concentric outer rings. This interpretation helps constrain the cooling history of Ganymede's icy crust.

Hathor's location near the south pole, combined with Ganymede's low axial and orbital tilt, makes it difficult to observe. Only Voyager 2 has properly imaged it, in July 1979. The upcoming Juice mission, scheduled to enter low orbit around Ganymede in July 2034, will allow much closer and repeated observations of polar regions like Hathor, potentially resolving uncertainties about its structure and formation. The crater also gives its name to the Hathor quadrangle (Jg15), underscoring its importance as a reference feature on Ganymede.

Did You Know?

• Hathor is a highly disrupted, dome-shaped penepalimpsest believed to be a very ancient crater in the process of being completely erased.
• The name Hathor was approved by the IAU in 1979, following the convention of naming Ganymede craters after deities from Ancient Middle Eastern mythology.
• Only Voyager 2 has properly imaged Hathor crater, capturing it in July 1979.
• A study by Thomas, Forni, and Masson probably mistakenly labeled Hathor crater as the Eastern Hathor basin and named the nearby Teshub crater as Hathor.