Palimpsest (planetary astronomy)
Encyclopedia
A palimpsest, in planetary astronomy
, is an ancient crater
on an icy moon
of the outer Solar System whose relief has disappeared due to creep of the icy surface ("viscous relaxation") or subsequent cryovolcanic outpourings, leaving a circular albedo feature, perhaps with a "ghost" of a rim. Icy surfaces of natural satellites like Callisto
and Ganymede
preserve hints of their history in these rings. A typical example is Memphis Facula
on Ganymede, a 340 km wide palimpsest.
Planetary science
Planetary science is the scientific study of planets , moons, and planetary systems, in particular those of the Solar System and the processes that form them. It studies objects ranging in size from micrometeoroids to gas giants, aiming to determine their composition, dynamics, formation,...
, is an ancient crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
on an icy moon
Icy moon
Icy moons are believed to be a common class of natural satellites or planetoids 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 ice II...
of the outer Solar System whose relief has disappeared due to creep of the icy surface ("viscous relaxation") or subsequent cryovolcanic outpourings, leaving a circular albedo feature, perhaps with a "ghost" of a rim. Icy surfaces of natural satellites like Callisto
Callisto (moon)
Callisto named after the Greek mythological figure of Callisto) is a moon of the planet Jupiter. It was discovered in 1610 by Galileo Galilei. It is the third-largest moon in the Solar System and the second largest in the Jovian system, after Ganymede. Callisto has about 99% the diameter of the...
and Ganymede
Ganymede (moon)
Ganymede is a satellite of Jupiter and the largest moon in the Solar System. It is the seventh moon and third Galilean satellite outward from Jupiter. Completing an orbit in roughly seven days, Ganymede participates in a 1:2:4 orbital resonance with the moons Europa and Io, respectively...
preserve hints of their history in these rings. A typical example is Memphis Facula
Memphis Facula
Memphis Facula is a palimpsest, or "ghost crater", on Ganymede, the largest of the Jovian satellites.Some 340 km across, it is situated in the south western part of Galileo Regio, a huge almost circular dark region on Ganymede's north eastern flank...
on Ganymede, a 340 km wide palimpsest.