Musa Patera
A potential cryovolcano caldera on Ganymede.
Musa Patera is a depression on Ganymede, Jupiter’s largest moon. Spanning 69 kilometers across, it features curved and arcuate cliffs and is thought to be a possible cryovolcanic caldera.
The feature is named after a wadi in Jordan, near the ancient site of Petra. Wadis are dry desert river valleys that only flow after heavy rain. The International Astronomical Union approved the name in 2015, following the convention that paterae on Ganymede are named after wadi river valleys in the Middle East.
Musa Patera lies in Ganymede’s southern hemisphere, near the border of two bright, grooved terrain regions: Sippar Sulcus and Mummu Sulcus. It sits northwest of the bright ray crater Osiris. To the east are two other paterae, Rum and Natrun, while the crater Bes lies to the northeast and the crater Khonsu to the south. The depression is within the Apsu quadrangle (Jg13). USGS maps place it in Mummu Sulcus, while NASA and JPL articles consider it part of Sippar Sulcus. Because Ganymede is tidally locked, Musa Patera is on the hemisphere that never faces Jupiter, so an observer there would never see the planet in the sky.
Images from the Galileo spacecraft show a lobate, flow-like feature within the depression—the strongest candidate yet for an icy volcanic lava flow on Ganymede. The structure is a prominent depression with scalloped walls and internal terraces, about 55 kilometers long and 17–20 kilometers wide. Inside lies a lobate deposit 7–10 kilometers wide, with outward-curving ridges that trend downslope toward a cross-cutting lane of grooved terrain. This morphology matches volcanic eruptions that may have carved a channel, emplaced a flow, and eroded the surface. Elevation data suggest the western caldera floor is similar in height to adjacent grooved terrain, but it drops eastward toward lower, smooth terrain that lacks grooves. However, as of 2025, evidence for cryovolcanism on Ganymede remains uncertain, and higher-resolution imaging from future missions is needed.
Only two space probes have clearly photographed Musa Patera: Voyager 2 and Galileo. Voyager 2 captured it during its July 1979 flyby, but the depression was too small and the probe too distant for useful detail. Galileo obtained excellent-resolution images during its orbit of Jupiter from December 1995 to September 2003.
Quick Facts
- Diameter
- 69 km
- Eponym
- Wadi Musa
Facts from the source article.
Lore & Background
Musa Patera is named after a wadi in the modern country of Jordan, near the famous archaeological site of Petra. The International Astronomical Union (IAU) chose the name in line with the convention that paterae on Ganymede should be named after wadi river valleys in the Middle East. The name was approved by the IAU in 2015.
The patera is located in the southern hemisphere of Ganymede, near the boundary between two bright grooved-terrain regions, Sippar Sulcus and Mummu Sulcus. It lies to the northwest of the bright ray crater Osiris, and to the east are Rum Patera and Natrun Patera, while to its northeast lies the crater Bes and to its south the crater Khonsu. Due to Ganymede's synchronous rotation, Musa Patera is on the hemisphere that never faces Jupiter, so an observer there would never see Jupiter in the sky.
Galileo spacecraft images reveal a lobate, flow-like feature within a depression measuring approximately 55 km in length and 17–20 km in width. The floor contains a lobate deposit 7–10 km wide with outward-curving ridges trending downslope. Elevation modeling indicates the westernmost caldera-floor material is comparable in height to adjacent grooved terrain but decreases eastward toward lower-lying smooth terrain. However, as of 2025, evidence for cryovolcanism on Ganymede remains ambiguous, and higher-resolution imaging is needed.
Reader's Guide
Musa Patera's significance lies in its status as a potential cryovolcano caldera on Ganymede, offering a rare window into possible icy volcanic processes on the largest moon of Jupiter. The Galileo spacecraft's images captured a lobate, flow-like feature that is the strongest candidate yet identified for an icy volcanic lava flow on Ganymede, with morphology consistent with volcanic eruptions that may have excavated a channel and emplaced a flow. This makes Musa Patera a key target for understanding whether Ganymede has experienced cryovolcanism, a process that could reveal internal heat and volatile cycling.
Despite this promise, the evidence remains ambiguous as of 2025, and higher-spatial-resolution imaging from future missions is needed to confirm its nature. The European Space Agency's Juice probe, launched in April 2023 and expected to arrive at Jupiter in July 2031, is planned to settle into a low orbit around Ganymede in 2034 at just 500 km altitude, which could achieve the high-resolution imaging necessary to determine whether Musa Patera is in fact a cryovolcano. The patera's location in the Apsu quadrangle and its disputed classification between Sippar Sulcus and Mummu Sulcus add to its geological interest, highlighting the complexity of Ganymede's surface.
Did You Know?
- The depression is 69 km wide and consists of curvilinear and arcuate cliffs.
- Galileo flew as low as 17,490 km above Musa Patera in May 1997, resolving details as small as 172 m.
- An observer at Musa Patera would never see Jupiter in the sky due to Ganymede's synchronous rotation.
More in Moons of Jupiter, Part 3 1-24
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced