Mons Gruithuisen Gamma

Mons Gruithuisen Gamma (γ) is a lunar dome^[1] that lies to the north of the crater Gruithuisen at the western edge of the Mare Imbrium.

Mons Gruithuisen Gamma
Mons Gruithuisen Gamma (left) and Delta (right) Lunar Orbiter 4 image
Highest point
Elevation	1500 m
Listing	Lunar mountains
Coordinates	36.56°N 40.72°W / 36.56; -40.72
Geography
Location	Near side of the Moon
Geology
Mountain type	Lunar dome

Oblique view from Apollo 15

Oblique view from LRO

Gruithuisen Gamma, Delta and North-West domes as viewed from Earth (8" Dobsonian telescope, untracked). Due to severe foreshortening, Gamma look like an upturned bathtub or loaf of bread.

This massif is shaped as a rounded dome in the surface, occupying a diameter of 20 km and climbing gently to a height of over 1500 meters.^[2][3] At the crest is a small crater.

This formation appears foreshortened when viewed from the Earth, and it has been described by Antonin Rukl as resembling an "upturned bathtub".^[4]

To the east lies the similar Mons Gruithuisen Delta (δ). Together they are often informally called the Gruithuisen domes. To the south of the Gruithuisen domes is a portion of Oceanus Procellarum that was named Sinus Viscositatis [it] by the IAU in December 2022.^[5]

The Gruithuisen domes differ from typical mare domes in that they're more mountain-like in their proportions, with a higher albedo and a rougher surface texture. The lava they're composed of might be the key to why they're different. It's thought to have a higher silica content, making it thicker, slower moving and faster cooling, enabling it to pile up into these structures. Such silicic volcanism is rare on the Moon, and it's still unclear how it can occur there at all, as on Earth it requires the presence of water and plate tectonics - factors absent on the Moon.^[6] This makes the region a compelling target for exploration.

Mons Gruithuisen Gamma was expected to be the landing site for Peregrine Mission One, which launched on January 8, 2024, on the maiden flight of the Vulcan Centaur rocket. The mission failed due to a leaky valve, precluding any attempt at landing.

Firefly Aerospace plans to use a Blue Ghost lander to deploy a rover at Gruithuisen Gamma in 2028 as part of NASA's Commercial Lunar Payload Services program.^[7] Lunar-VISE instruments on the lander and rover will map local variations in geological compositions and thermophysical properties^[8]

A small (150 m diameter) crater located near the summit of Mons Gruithuisen Gamma was named Mareta by the IAU in June 2025.^[9]

Mareta crater

See also

• List of mountains on the Moon
• Volcanism on the Moon