Erichthonius (crater)
A deformed central-pit crater on Ganymede's far hemisphere.
Erichthonius is a crater on Ganymede, Jupiter’s largest moon, situated just south of the equator. It measures about 31 kilometers (19 miles) across and features a pit at its center. The crater’s name comes from a king of Troy, who, depending on the mythological source, was either the grandfather (per Homer) or the father (per Hyginus) of the Trojan prince Ganymede, for whom the moon is named. The International Astronomical Union approved the name in 1997, following its convention of naming Ganymede’s craters after deities, heroes, and places from ancient Near Eastern myths, or after relatives of Ganymede.
Geographically, Erichthonius lies a few kilometers south of Ganymede’s equator, within the southern part of Marius Regio, a dark, ancient region. It sits at the northeastern corner where two younger, grooved terrains—Erech Sulcus and Sippar Sulcus—meet. To the west are Erech Sulcus and the craters Amset and Eshmun; to the south lies Sippar Sulcus; to the north and east are several unnamed ray and halo craters. The crater is located in the Uruk Sulcus quadrangle (designated Jg8). Because Ganymede is tidally locked to Jupiter, one hemisphere always faces the planet and the other never does. Erichthonius sits on the far side, so an observer at the crater would never see Jupiter in the sky.
Morphologically, Erichthonius is a central-pit crater that has been geologically deformed. Several curvy grabens run across it from west to east, indicating tectonic damage to its floor and rim. Unlike many other strained craters on Ganymede, the faults here show graben morphology rather than tilt-block normal faulting, meaning extension occurred as blocks dropped down between pairs of normal faults. The crater floor has experienced moderate extensional strain, with elongation estimated at over 10%, consistent with extension along nearby subparallel ridges and troughs. While some of Ganymede’s rift zones show extreme strains exceeding 100%, Erichthonius is a more moderate example, preserving much of its original structure and offering insight into ridge-and-trough fault zones. It is one of the least deformed strained craters, compared to examples like Nefertum and Saltu.
Geologically, Erichthonius is classified as a pit crater.
Quick Facts
- Diameter
- 31 km
- Eponym
- Εριχθόνιος της Τρωάδος (Erichthonius the Trojan)
Facts from the source article.
Lore & Background
Erichthonius is named after a king of Troy who, according to Homer, was the grandfather of the mythological Trojan prince Ganymede, or according to Hyginus, the father of Ganymede. The name follows the International Astronomical Union's convention of naming craters on Ganymede after deities, heroes, and places from Ancient Near Eastern mythologies, or after relatives of Ganymede. The IAU approved the name in 1997.
The crater sits at the junction of two younger, grooved terrains—Erech Sulcus and Sippar Sulcus—at their northeastern corner. It is located on the hemisphere of Ganymede that never faces Jupiter, so an observer at the crater would never see Jupiter in the sky. Voyager 2 first imaged Erichthonius in July 1979 but could not capture its details due to the crater's small size and the probe's distance. Voyager 1 flew by the opposite hemisphere and did not image it at all. Galileo conducted a targeted flyby in May 1997, revealing that the crater floor was fractured and deformed by several grabens and cliffs, strongly indicating tectonic activity.
Reader's Guide
Erichthonius is significant as one of the least deformed strained craters on Ganymede, preserving much of its original crater structure despite tectonic stretching. Its shape appears to have been geologically deformed and strained, with several curvy grabens running across the crater from west to east, showing damage to the floor and rim. Unlike many other strained or deformed craters on Ganymede, the faults within Erichthonius display graben morphology rather than tilt-block normal faulting, indicating extension occurred through the down-dropping of blocks between pairs of normal faults. Analyses of the crater's floor show moderate extensional strain with elongation greater than 10%, consistent with extension along nearby subparallel ridges and troughs. While some of Ganymede's rift zones display extreme strains exceeding 100%, Erichthonius represents a more moderate example, providing insight into the effects of ridge-and-trough fault zones. The European Space Agency's Juice orbiter, scheduled to arrive at Jupiter in July 2031, will eventually settle into a low polar orbit around Ganymede, allowing higher-resolution images that may help determine the causes of its deformation.
Did You Know?
- The crater's name was approved by the IAU in 1997.
- Galileo conducted a targeted flyby of Erichthonius in May 1997, revealing tectonic deformation.
Frequently Asked Questions
What is Erichthonius (crater)?
Erichthonius is a roughly 31-kilometer-wide impact crater located on Ganymede, Jupiter's largest moon. It sits just a few kilometers south of the moon's equator within the Marius Regio region on the far hemisphere.
What does Erichthonius (crater) look like physically?
The crater is classified as a deformed central-pit type, meaning it has a noticeable pit or depression at its center rather than a smooth floor. Its overall structure shows signs of having been altered after the original impact event.
Who is Erichthonius (crater) named after?
The name honors a king of Troy from Greek mythology who is identified as either the grandfather (in Homer's account) or the father (in Hyginus's version) of the young prince Ganymede. This relative connection is why the IAU approved the name for a crater on the moon that bears the prince's own name.
When was the name Erichthonius officially approved?
The International Astronomical Union ratified the designation in 1997, consistent with its practice of assigning Ganymede's craters names drawn from ancient Near Eastern deities, heroes, mythological places, or their close relatives.
Which spacecraft have observed Erichthonius (crater)?
Voyager 2 captured the first images of the crater during its July 1979 flyby of Ganymede. The Galileo orbiter later performed a targeted flyby in May 1997, providing additional close-up data of the feature.
More in Moons of Jupiter, Part 3 1-24
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