page_title: Planetary surface
section_title: Rare surface occurrences
hierarchical_section_title: Planetary surface / Surface materials / Rare surface occurrences
context_page_description: A planetary surface is where the solid material of the outer crust on certain types of astronomical objects contacts the atmosphere or outer space. Planetary surfaces are found on solid objects of planetary mass, including terrestrial planets, dwarf planets, natural satellites, planetesimals and many other small Solar System bodies. The study of planetary surfaces is a field of planetary geology known as surface geology, but also a focus of a number of fields including planetary cartography, topography, geomorphology, atmospheric sciences, and astronomy. Land is the term given to non-liquid planetary surfaces. The term landing is used to describe the collision of an object with a planetary surface and is usually at a velocity in which the object can remain intact and remain attached.
  In differentiated bodies, the surface is where the crust meets the planetary boundary layer. Anything below this is regarded as being sub-surface or sub-marine. Most bodies more massive than super-Earths, including stars and gas giants, as well as smaller gas dwarfs, transition contiguously between phases, including gas, liquid, and solid. As such, they are generally regarded as lacking surfaces.
context_section_description: Surface liquid, while abundant on Earth (the largest body of surface liquid being the World Ocean) is rare elsewhere, a notable exception being Titan which has the largest known hydrocarbon lake system while surface water, abundant on Earth and essential to all known forms of life is thought only to exist as Seasonal flows on warm Martian slopes and in the habitable zones of other planetary systems.
  Volcanism can cause flows such as lava on the surface of geologically active bodies (the largest being the Amirani (volcano) flow on Io).  Many of Earth's Igneous rocks are formed through processes rare elsewhere, such as the presence of volcanic magma and water.  Surface mineral deposits such as olivine and hematite discovered on Mars by lunar rovers provide direct evidence of past stable water on the surface of Mars.
  Apart from water, many other abundant surface materials are unique to Earth in the Solar System as they are not only organic but have formed due to the presence of life – these include carbonate hardgrounds, limestone, vegetation and artificial structures although the latter is present due to probe exploration (see also List of artificial objects on extra-terrestrial surfaces).
caption: Shoreline on Earth – land, sea, sand, and eroded clays. Earth's surface consists of a wide variety of water, carbon and silicon rich material.
exif: {}