A palimpsest , in planetary astronomy, is an ancient

crater A crater is a landform consisting of a hole or depression (geology), depression on a planetary surface, usually caused either by an object hitting the surface, or by geological activity on the planet. A crater has classically been described ...

that has been degraded over time. They may also be referred to as "ghost craters", "degraded craters", "buried craters", or "pathological craters". Palimpsests have been identified on Mercury, the Earth, the Moon, Mars, Ganymede, Callisto, and possibly even Titan. On Mars, these features are morphologically described as craters that are "flat-floored, rimless, extremely shallow, without central peaks, and would probably represent what remains after erosion." On an

icy moon Icy moons are a class of natural satellites with surfaces composed mostly of ice. An icy moon may harbor an ocean underneath the surface, and possibly include a rocky core of silicate or metallic rocks. It is thought that they may be composed of i ...

of the

outer Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sol ...

, a palimpsest is a crater whose

relief Relief is a sculpture, sculptural method in which the sculpted pieces remain attached to a solid background of the same material. The term ''wikt:relief, relief'' is from the Latin verb , to raise (). To create a sculpture in relief is to give ...

has disappeared due to creep of the icy surface ("viscous relaxation") or subsequent

cryovolcanic A cryovolcano (sometimes informally referred to as an ice volcano) is a type of volcano that erupts gases and volatile material such as liquid water, ammonia, and hydrocarbons. The erupted material is collectively referred to as ''cryolava''; ...

outpourings, leaving a circular albedo feature, perhaps with a "ghost" of a rim. Icy surfaces of natural satellites like

Callisto CALLISTO (''Cooperative Action Leading to Launcher Innovation in Stage Toss-back Operations'') is a reusable VTVL Prototype, demonstrator propelled by a small 40 kN Japanese LOX-LH2 rocket engine. It is being developed jointly by the CNES, French ...

and Ganymede preserve hints of their history in these rings. A typical example is

Memphis Facula Memphis Facula is a Palimpsest (planetary astronomy), palimpsest, or "ghost crater", on Ganymede (moon), Ganymede, the largest of the Moons of Jupiter, Jovian satellites. About 360 km across, it is situated in the southwestern part of Gali ...

on Ganymede, a 340 km wide palimpsest.

References

Space science Planetary geology Surface features of bodies of the Solar System Impact craters {{Planetary-geology-stub

See also

References