Partially Buried Craters
Partially Buried Craters and Craterlets(special features list)
On rather rare occasions it is possible for a lunar crater to be partially inundated by the in-fall of material from a neighboring hill, giving it the appearance of a sharply outlined partial arc at the foot of a slope. This should not be confused with the more common ghost craters (such as Lamont or Stadius) whose bowls have been filled with surrounding lavas leaving visible only a slight hint of the top of the original rim.
- The 3-km crater at the base of the southeastern slope Euler Gamma (a discontinued IAU name for a hill south-southeast of Euler) is an excellent example of a half-buried crater. It is nicely visible on Lunar Orbiter Frame IV-133H3, as well as on many Apollo images referred to on the Euler page. It also makes an interesting telescopic target as indicated by Harold Hill's description and drawing of it on pages 52-53 of his book A Portfolio of Lunar Drawings.
- There is a partially buried crater at the base of the inner slope of the eastern part of Maskelyne F, an incomplete ring in Mare Tranquillitatis. It can be seen, near the south end of the curve, in Lunar Orbiter Frame II-005. Note that the crater near the middle which also looks half-buried is only half in shadow.
- A small, partially-buried crater can be seen along the eastern edge of Mons Gruithuisen Gamma (Lunar Orbiter Frame IV-145H1); as well as an apparently rille-related depression at the southeastern tip of the same structure, partially covered by the advance of the hill.
- A curious plateau-like "interrupted disc" is noticeable at the south-southeastern part of Sinas's rim.
- A couple of partially buried craterlets at the northern part of the unnamed dome-like hillock just south of Nicollet B in Mare Nubium.
- Peter Schultz describes the half-buried crater at the foot of Euler gamma (illustrated above) on pp. 304-305 of Moon morphology. He offers three hypotheses for its formation: (1) that the impact destabilized the slope precipitating a landslide into it; (2) that the crater formed next to a loosely consolidated hill subject to gradual mass wasting which has caused it to subsequently broaden and encroach on the crater; (3) that the hill is an extrusion of extremely viscous volcanic material that has flowed into the crater without filling its floor. He seems to feel the first possibility is the most likely with the hill being subject to more rapid weathering than the crater, with its relatively sharply preserved rim. Harold Hill also favors the hypothesis of in-fall by scree-like debris streaming down from the slopes of Euler Gamma.
- Partially buried craters on the slopes of lunar hills (as opposed to at their feet) appear to be very rare, apparently because they are rapidly (geologically speaking) erased by the downfalling material.