
A planetary surface is where the solid or liquid material of certain types of
astronomical object
An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often us ...
s contacts the
atmosphere
An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. ...
or
outer space
Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ...
. Planetary surfaces are found on solid objects of
planetary mass
In astronomy, planetary mass is a measure of the mass of a planet-like astronomical object. Within the Solar System, planets are usually measured in the astronomical system of units, where the unit of mass is the solar mass (), the mass of the Sun ...
, including
terrestrial planet
A terrestrial planet, telluric planet, or rocky planet, is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets accepted by the IAU are the inner planets closest to the Sun: Mercury, ...
s (including
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surf ...
),
dwarf planet
A dwarf planet is a small planetary-mass object that is in direct orbit of the Sun, smaller than any of the eight classical planets but still a world in its own right. The prototypical dwarf planet is Pluto. The interest of dwarf planets to ...
s,
natural satellite
A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons ...
s,
planetesimal
Planetesimals are solid objects thought to exist in protoplanetary disks and debris disks. Per the Chamberlin–Moulton planetesimal hypothesis, they are believed to form out of cosmic dust grains. Believed to have formed in the Solar System ...
s and many other
small Solar System bodies
A small Solar System body (SSSB) is an object in the Solar System that is neither a planet, a dwarf planet, nor a natural satellite. The term was first defined in 2006 by the International Astronomical Union (IAU) as follows: "All other objects, ...
(SSSBs). The study of planetary surfaces is a field of
planetary geology
Planetary geology, alternatively known as astrogeology or exogeology, is a planetary science discipline concerned with the geology of the celestial bodies such as the planets and their moons, asteroids, comets, and meteorites. Although the ge ...
known as surface geology, but also a focus of a number of fields including
planetary cartography
Planetary cartography, or cartography of extraterrestrial objects (CEO), is the cartography of solid objects outside of the Earth. Planetary maps can show any spatially mapped characteristic (such as topography, geology, and geophysical propertie ...
,
topography
Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps.
Topography is a field of geoscience and planetary s ...
,
geomorphology
Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or ...
,
atmospheric sciences, and
astronomy
Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest ...
. Land (or ground) is the term given to non-liquid planetary surfaces. The term ''
landing
Landing is the last part of a flight, where a flying animal, aircraft, or spacecraft returns to the ground. When the flying object returns to water, the process is called alighting, although it is commonly called "landing", "touchdown" or ...
'' 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
In meteorology, the planetary boundary layer (PBL), also known as the atmospheric boundary layer (ABL) or peplosphere, is the lowest part of the atmosphere and its behaviour is directly influenced by its contact with a planetary surface. On Ea ...
. Anything below this is regarded as being sub-surface or sub-marine. Most bodies more massive than
super-Earth
A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively.
The term "super-Earth" refers only to ...
s, including
star
A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...
s and
gas giants
A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" ...
, as well as smaller
gas dwarf
A Mini-Neptune (sometimes known as a gas dwarf or transitional planet) is a planet less massive than Neptune but resembling Neptune in that it has a thick hydrogen– helium atmosphere, probably with deep layers of ice, rock or liquid oceans (ma ...
s, transition contiguously between phases, including gas, liquid, and solid. As such, they are generally regarded as lacking surfaces.
Planetary surfaces and surface life are of particular interest to
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
s as it is the primary
habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
of the species, which has
evolved
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation te ...
to move over land and
breathe air
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...
. Human
space exploration
Space exploration is the use of astronomy and space technology to explore outer space. While the exploration of space is carried out mainly by astronomers with telescopes, its physical exploration though is conducted both by uncrewed rob ...
and
space colonization
Space colonization (also called space settlement or extraterrestrial colonization) is the use of outer space or celestial bodies other than Earth for permanent habitation or as extraterrestrial territory.
The inhabitation and territor ...
therefore focuses heavily on them. Humans have only directly explored the surface of Earth and the Moon. The vast distances and complexities of space makes direct exploration of even
near-Earth object
A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU) ...
s dangerous and expensive. As such, all other exploration has been indirect via
space probe
A space probe is an artificial satellite that travels through space to collect scientific data. A space probe may orbit Earth; approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other planetary bodies; or ...
s.
Indirect observations by flyby or orbit currently provide insufficient information to confirm the composition and properties of planetary surfaces. Much of what is known is from the use of techniques such as
astronomical spectroscopy
Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light, ultraviolet, X-ray, infrared and radio waves that radiate from stars and other ...
and
sample return
A sample-return mission is a spacecraft mission to collect and return samples from an extraterrestrial location to Earth for analysis. Sample-return missions may bring back merely atoms and molecules or a deposit of complex compounds such as lo ...
.
Lander spacecraft have explored the surfaces of planets
Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin atmos ...
and
Venus
Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...
. Mars is the only other planet to have had its surface explored by a mobile surface probe (rover).
Titan
Titan most often refers to:
* Titan (moon), the largest moon of Saturn
* Titans, a race of deities in Greek mythology
Titan or Titans may also refer to:
Arts and entertainment
Fictional entities
Fictional locations
* Titan in fiction, fiction ...
is the only non-planetary object of
planetary mass
In astronomy, planetary mass is a measure of the mass of a planet-like astronomical object. Within the Solar System, planets are usually measured in the astronomical system of units, where the unit of mass is the solar mass (), the mass of the Sun ...
to have been explored by lander. Landers have explored several smaller bodies including
433 Eros
Eros ( minor planet designation: (433) Eros), provisional designation is a stony asteroid of the Amor group and the first discovered and second-largest near-Earth object with an elongated shape and a mean diameter of approximately . V ...
(2001),
25143 Itokawa
25143 Itokawa (provisional designation ) is a sub-kilometer near-Earth object of the Apollo group and a potentially hazardous asteroid. It was discovered by the LINEAR program in 1998 and later named after Japanese rocket engineer Hideo Itokawa ...
(2005),
Tempel 1
Tempel 1 (official designation: 9P/Tempel) is a periodic Jupiter-family comet discovered by Wilhelm Tempel in 1867. It completes an orbit of the Sun every 5.5 years. Tempel 1 was the target of the ''Deep Impact'' space mission, which photogra ...
(2005),
67P/Churyumov–Gerasimenko
67P/Churyumov–Gerasimenko (abbreviated as 67P or 67P/C–G) is a Jupiter-family comet, originally from the Kuiper belt, with a current orbital period of 6.45 years, a rotation period of approximately 12.4 hours and a maximum velocity of . Ch ...
(2014),
162173 Ryugu
162173 Ryugu, provisional designation , is a near-Earth object and a potentially hazardous asteroid of the Apollo group. It measures approximately in diameter and is a dark object of the rare spectral type Cb, with qualities of both a C-type ...
(2018) and
101955 Bennu
101955 Bennu (provisional designation ) is a carbonaceous asteroid in the Apollo group discovered by the LINEAR Project on 11 September 1999. It is a potentially hazardous object that is listed on the Sentry Risk Table and has the highest cumu ...
(2020). Surface samples have been collected from the Moon (returned 1969), 25143 Itokawa (returned 2010), 162173 Ryugu and 101955 Bennu.
Distribution and conditions
Planetary surfaces are found throughout the
Solar System
The Solar System Capitalization 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 "Solar ...
, from the inner
terrestrial planet
A terrestrial planet, telluric planet, or rocky planet, is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets accepted by the IAU are the inner planets closest to the Sun: Mercury, ...
s, to the
asteroid belt
The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, called ...
, the natural satellites of the
gas giant
A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" ...
planets and beyond to the
Trans-Neptunian object
A trans-Neptunian object (TNO), also written transneptunian object, is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has a semi-major axis of 30.1 astronomical units (au).
Typicall ...
s. Surface conditions, temperatures and
terrain
Terrain or relief (also topographical relief) involves the vertical and horizontal dimensions of land surface. The term bathymetry is used to describe underwater relief, while hypsometry studies terrain relative to sea level. The Latin w ...
vary significantly due to a number of factors including
Albedo
Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refl ...
often generated by the surfaces itself. Measures of surface conditions include
surface area
The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of ...
,
surface gravity
The surface gravity, ''g'', of an astronomical object is the gravitational acceleration experienced at its surface at the equator, including the effects of rotation. The surface gravity may be thought of as the acceleration due to gravity experien ...
,
surface temperature Surface temperature is the temperature at a surface.
Specifically, it may refer to:
* Surface air temperature, the temperature of the air near the surface of the earth
* Sea surface temperature, the temperature of water close to the ocean's sur ...
and
surface pressure Surface pressure may refer to:
* " Surface Pressure", a song from the film ''Encanto'' (2021)
* Surface pressure in physical chemistry
* Surface pressure within the Earth's atmosphere
{{dab ...
. Surface stability may be affected by erosion through
Aeolian processes
Aeolian processes, also spelled eolian, pertain to wind activity in the study of geology and weather and specifically to the wind's ability to shape the surface of the Earth (or other planets). Winds may erode, transport, and deposit materials ...
,
hydrology
Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...
,
subduction
Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...
,
volcanism
Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the Earth#Surface, surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the su ...
,
sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...
or
seismic
Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...
activity. Some surfaces are dynamic while others remain unchanged for millions of years.
Exploration
Distance, gravity, atmospheric conditions (extremely low or extremely high
atmospheric pressure
Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibar ...
) and unknown factors make exploration both costly and risky. This necessitates the space probes for early exploration of planetary surfaces. Many probes are stationary have a limited study range and generally survive on extraterrestrial surfaces for a short period, however mobile probes (rovers) have surveyed larger surface areas.
Sample return mission
A sample-return mission is a spacecraft mission to collect and return samples from an extraterrestrial location to Earth for analysis. Sample-return missions may bring back merely atoms and molecules or a deposit of complex compounds such as lo ...
s allow scientist to study extraterrestrial surface materials on Earth without having to send a crewed mission, however is generally only feasible for objects with low gravity and atmosphere.
Past missions
The first extraterrestrial planetary surface to be explored was the
lunar surface
The geology of the Moon (sometimes called selenology, although the latter term can refer more generally to " lunar science") is quite different from that of Earth. The Moon lacks a true atmosphere, which eliminates erosion due to weather. It does ...
by
Luna 2
''Luna 2'' ( rus, Луна 2}), originally named the Second Soviet Cosmic Rocket and nicknamed Lunik 2 in contemporaneous media, was the sixth of the Soviet Union's Luna programme spacecraft launched to the Moon, E-1 No.7. It was the first spac ...
in 1959. The first and only human exploration of an extraterrestrial surface was the Moon, the
Apollo program included the first moonwalk on July 20, 1969, and successful return of extraterrestrial surface samples to Earth.
Venera 7
Venera 7 (russian: Венера-7, lit=Venus 7) was a Soviet spacecraft, part of the Venera series of probes to Venus. When it landed on the Venusian surface on 15 December 1970, it became the first spacecraft to soft land on another planet and ...
was the first landing of a probe on another planet on December 15, 1970.
Mars 3
Mars 3 was a robotic space probe of the Soviet Mars program, launched May 28, 1971, nine days after its twin spacecraft Mars 2. The probes were identical robotic spacecraft launched by Proton-K rockets with a Blok D upper stage, each consist ...
"soft landed" and returned data from Mars on August 22, 1972, the first rover on Mars was
Mars Pathfinder
''Mars Pathfinder'' (''MESUR Pathfinder'') is an American robotic spacecraft that landed a base station with a roving probe on Mars in 1997. It consisted of a lander, renamed the Carl Sagan Memorial Station, and a lightweight, wheeled roboti ...
in 1997, the
Mars Exploration Rover
NASA's Mars Exploration Rover (MER) mission was a robotic space mission involving two Mars rovers, '' Spirit'' and '' Opportunity'', exploring the planet Mars. It began in 2003 with the launch of the two rovers to explore the Martian surface ...
has been studying the surface of the red planet since 2004.
NEAR Shoemaker
''Near Earth Asteroid Rendezvous – Shoemaker'' (''NEAR Shoemaker''), renamed after its 1996 launch in honor of planetary scientist Eugene Shoemaker, was a robotic space probe designed by the Johns Hopkins University Applied Physics Labora ...
was the first to soft land on an asteroid –
433 Eros
Eros ( minor planet designation: (433) Eros), provisional designation is a stony asteroid of the Amor group and the first discovered and second-largest near-Earth object with an elongated shape and a mean diameter of approximately . V ...
in February 2001 while
Hayabusa
was a robotic spacecraft developed by the Japan Aerospace Exploration Agency (JAXA) to return a sample of material from a small near-Earth asteroid named 25143 Itokawa to Earth for further analysis.
''Hayabusa'', formerly known as MUSES-C ...
was the first to return samples from
25143 Itokawa
25143 Itokawa (provisional designation ) is a sub-kilometer near-Earth object of the Apollo group and a potentially hazardous asteroid. It was discovered by the LINEAR program in 1998 and later named after Japanese rocket engineer Hideo Itokawa ...
on 13 June 2010. ''
Huygens
Huygens (also Huijgens, Huigens, Huijgen/Huygen, or Huigen) is a Dutch patronymic surname, meaning "son of Hugo". Most references to "Huygens" are to the polymath Christiaan Huygens. Notable people with the surname include:
* Jan Huygen (1563– ...
'' soft landed and returned data from
Titan
Titan most often refers to:
* Titan (moon), the largest moon of Saturn
* Titans, a race of deities in Greek mythology
Titan or Titans may also refer to:
Arts and entertainment
Fictional entities
Fictional locations
* Titan in fiction, fiction ...
on January 14, 2005.
There have been many failed attempts, more recently
Fobos-Grunt
Fobos-Grunt or Phobos-Grunt (russian: link=no, Фобос-Грунт, where ''грунт'' refers to the ''ground'' in the narrow geological meaning of any type of soil or rock exposed on the surface) was an attempted Russian sample return mis ...
, a sample return mission aimed at exploring the surface of
Phobos
Phobos (Greek for "fear") most commonly refers to:
* Phobos (moon), a moon of Mars
* Phobos (mythology), the Greek god and personification of fear and panic
Phobos may also refer to:
Comics
* Phobos (Marvel Comics)
* Phobos (''W.I.T.C.H.''), a ...
.
Surface materials
The most common planetary surface material in the Solar System appears to be water
ice
Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaq ...
. Surface ice is found as close to the Sun as Mercury but is more abundant beyond Mars. Other surfaces include solid matter in combinations of
rock
Rock most often refers to:
* Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids
* Rock music, a genre of popular music
Rock or Rocks may also refer to:
Places United Kingdom
* Rock, Caerphilly, a location in Wales ...
,
regolith
Regolith () is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestri ...
and
frozen chemical element
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
s and
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one ele ...
s. In general, ice predominates planetary surfaces beyond the
frost line
The frost line—also known as frost depth or freezing depth—is most commonly the depth to which the groundwater in soil is expected to freeze. The frost depth depends on the climatic conditions of an area, the heat transfer properties of th ...
, while closer to the Sun, rock and regolith predominate.
Mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ...
s and
hydrates may also be present in smaller quantities on many planetary surfaces.
Rare surface occurrences

Surface liquid, while abundant on Earth (the largest body of surface liquid being the
World Ocean
The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wor ...
) is rare elsewhere, a notable exception being
Titan
Titan most often refers to:
* Titan (moon), the largest moon of Saturn
* Titans, a race of deities in Greek mythology
Titan or Titans may also refer to:
Arts and entertainment
Fictional entities
Fictional locations
* Titan in fiction, fiction ...
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
Seasonal flows on warm Martian slopes (also called recurring slope lineae, recurrent slope lineae and RSL) are thought to be salty water flows occurring during the warmest months on Mars, or alternatively, dry grains that "flow" downslope of at le ...
and in the
habitable zone
In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.J. F. Kas ...
s of other
planetary system
A planetary system is a set of gravitationally bound non-stellar objects in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although such systems may also consis ...
s.
Volcanism
Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the Earth#Surface, surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the su ...
can cause flows such as
lava
Lava is molten or partially molten rock ( magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or ...
on the surface of geologically active bodies (the largest being the
Amirani (volcano)
Amirani is an active volcano on Jupiter's moon Io, the inner-most of the Galilean Moons. It is located on Io's leading hemisphere at . The volcano is responsible for the largest active lava flow in the entire Solar System, with recent flows dwar ...
flow on Io). Many of Earth's
Igneous rock
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or l ...
s are formed through processes rare elsewhere, such as the presence of volcanic magma and water. Surface mineral deposits such as
olivine
The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...
and
hematite
Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of ...
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
Organic may refer to:
* Organic, of or relating to an organism, a living entity
* Organic, of or relating to an anatomical organ
Chemistry
* Organic matter, matter that has come from a once-living organism, is capable of decay or is the product o ...
but have formed due to the presence of life – these include
carbonate hardgrounds
Carbonate hardgrounds are surfaces of synsedimentarily cemented carbonate layers that have been exposed on the seafloor (Wilson and Palmer, 1992). A hardground is essentially, then, a lithified seafloor. Ancient hardgrounds are found in limestone ...
,
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...
,
vegetation
Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic charact ...
and
artificial
Artificiality (the state of being artificial or manmade) is the state of being the product of intentional human manufacture, rather than occurring nature, naturally through processes not involving or requiring human activity.
Connotations
Artific ...
structures although the latter is present due to probe exploration (see also
List of artificial objects on extra-terrestrial surfaces
This is a partial list of artificial objects left on extraterrestrial surfaces.
Artificial objects on Venus
Artificial objects on the Moon
Artificial objects on Mars
Artificial objects on other extraterrestrial bodies
Estimated ...
).
Extraterrestrial Organic compounds
Increasingly organic compounds are being found on objects throughout the Solar System. While unlikely to indicate the presence of extraterrestrial life, all known life is based on these compounds. Complex carbon molecules may form through various complex chemical interactions or delivered through impacts with small solar system objects and can combine to form the "building blocks" of
Carbon-based life Carbon-based may refer to:
* Biology
* based on Carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It ...
. As organic compounds are often
volatile
Volatility or volatile may refer to:
Chemistry
* Volatility (chemistry), a measuring tendency of a substance or liquid to vaporize easily
* Relative volatility, a measure of vapor pressures of the components in a liquid mixture
* Volatiles, a gr ...
, their persistence as a solid or liquid on a planetary surface is of scientific interest as it would indicate an intrinsic source (such as from the object's interior) or residue from larger quantities of organic material preserved through special circumstances over geological timescales, or an extrinsic source (such as from past or recent collision with other objects).
Radiation makes the detection of organic matter difficult, making its detection on atmosphereless objects closer to the Sun extremely difficult.
Examples of likely occurrences include:
*
Tholin
Tholins (after the Greek (') "hazy" or "muddy"; from the ancient Greek word meaning "sepia ink") are a wide variety of organic compounds formed by solar ultraviolet or cosmic ray irradiation of simple carbon-containing compounds such as carbon ...
s – many Trans Neptunian Objects including Pluto-Charon,
Titan,
Triton,
Eris,
Sedna, 28978 Ixion,
90482 Orcus,
24 Themis
Themis (minor planet designation: 24 Themis) is one of the largest asteroids in the asteroid belt. It is also the largest member of the Themistian family. It was discovered by Annibale de Gasparis on 5 April 1853. It is named after Themis, t ...
pdf version
accessed 28 Feb. 2018).
*
Methane clathrate
Methane clathrate (CH4·5.75H2O) or (8CH4·46H2O), also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound (more specifically, a clathrate hydrate) in which a large am ...
(CH
4·5.75H
2O) –
Oberon
Oberon () is a king of the fairies in medieval and Renaissance literature. He is best known as a character in William Shakespeare's play ''A Midsummer Night's Dream'', in which he is King of the Fairies and spouse of Titania, Queen of the Fair ...
,
Titania,
Umbriel,
Pluto
Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest k ...
, 90482 Orcus,
Comet 67P
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are ...
= On Mars
=
Martian exploration including samples taken by on the ground rovers and spectroscopy from orbiting satellites have revealed the presence of a number of complex organic molecules, some of which could be biosignatures in the search for life.
*
Thiophene
Thiophene is a heterocyclic compound with the formula C4H4S. Consisting of a planar five-membered ring, it is aromatic as indicated by its extensive substitution reactions. It is a colorless liquid with a benzene-like odor. In most of its react ...
()
*
Polythiophene
Polythiophenes (PTs) are polymerized thiophenes, a sulfur heterocycle. The parent PT is an insoluble colored solid with the formula (C4H2S)n. The rings are linked through the 2- and 5-positions. Poly(alkylthiophene)s have alkyl substituents ...
(polymer of )
*
Methanethiol
Methanethiol (also known as methyl mercaptan) is an organosulfur compound with the chemical formula . It is a colorless gas with a distinctive putrid smell. It is a natural substance found in the blood, brain and feces of animals (including huma ...
()
*
Dimethyl sulfide
Dimethyl sulfide (DMS) or methylthiomethane is an organosulfur compound with the formula (CH3)2S. Dimethyl sulfide is a flammable liquid that boils at and has a characteristic disagreeable odor. It is a component of the smell produced from co ...
()
= On Ceres
=
*
Ammonium bicarbonate
Ammonium bicarbonate is an inorganic compound with formula (NH4)HCO3. The compound has many names, reflecting its long history. Chemically speaking, it is the bicarbonate salt of the ammonium ion. It is a colourless solid that degrades readily to ...
().
*
Gilsonite
Asphaltite (also known as uintahite, asphaltum, gilsonite or oil sands) is a naturally occurring soluble solid hydrocarbon, a form of asphalt (or bitumen) with a relatively high melting temperature. Its large-scale production occurs in the Uintah ...
= On Enceladus
=
*
Methylamine
Methylamine is an organic compound with a formula of . This colorless gas is a derivative of ammonia, but with one hydrogen atom being replaced by a methyl group. It is the simplest primary amine.
Methylamine is sold as a solution in methanol, ...
/Ethylamine
(
CH3 NH2)
*
Acetaldehyde
Acetaldehyde (IUPAC systematic name ethanal) is an organic chemical compound with the formula CH3 CHO, sometimes abbreviated by chemists as MeCHO (Me = methyl). It is a colorless liquid or gas, boiling near room temperature. It is one of the ...
(
CH3 CHO
Cho or CHO may refer to:
People
* Chief Happiness Officer
Surnames
* Cho (Korean surname), one romanization of the common Korean surname
* Zhuo (), romanized Cho in Wade–Giles, Chinese surname
* Cho, a Minnan romanization of the Chinese sur ...
)
= On Comet 67P
=
The space probe
Philae (spacecraft)
''Philae'' ( or ) was a robotic European Space Agency lander that accompanied the ''Rosetta'' spacecraft until it separated to land on comet 67P/Churyumov–Gerasimenko, ten years and eight months after departing Earth. On 12 November 2014, ...
discovered the following organic compounds on the surface of Comet 67P:.
*
Acetamide
Acetamide (systematic name: ethanamide) is an organic compound with the formula CH3CONH2. It is the simplest amide derived from acetic acid. It finds some use as a plasticizer and as an industrial solvent. The related compound Dimethylacetamide, ...
()
*
Acetone
Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour.
Acetone is miscible wi ...
(CH
3)
2CO
*
Methyl isocyanate
Methyl isocyanate (MIC) is an organic compound with the molecular formula CH3NCO. Synonyms are isocyanatomethane and methyl carbylamine. Methyl isocyanate is an intermediate chemical in the production of carbamate pesticides (such as carbaryl, ...
()
*
Propionaldehyde
Propionaldehyde or propanal is the organic compound with the formula CH3CH2CHO. It is the 3-carbon aldehyde. It is a colourless, flammable liquid with a slightly fruity odour. It is produced on a large scale industrially.
Production
Propionalde ...
()
Inorganic materials

The following is a non-exhaustive list of surface materials that occur on more than one planetary surface along with their locations in order of distance from the Sun. Some have been detected by spectroscopy or direct imaging from orbit or flyby.
*
Ice
Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaq ...
() – Mercury (polar); Earth-Moon system; Mars (polar);
Ceres and some asteroids such as
24 Themis
Themis (minor planet designation: 24 Themis) is one of the largest asteroids in the asteroid belt. It is also the largest member of the Themistian family. It was discovered by Annibale de Gasparis on 5 April 1853. It is named after Themis, t ...
; Jupiter moons –
Europa
Europa may refer to:
Places
* Europe
* Europa (Roman province), a province within the Diocese of Thrace
* Europa (Seville Metro), Seville, Spain; a station on the Seville Metro
* Europa City, Paris, France; a planned development
* Europa Cliff ...
,
Ganymede and
Callisto Callisto most commonly refers to:
* Callisto (mythology), a nymph
*Callisto (moon), a moon of Jupiter
Callisto may also refer to:
Art and entertainment
*'' Callisto series'', a sequence of novels by Lin Carter
*''Callisto'', a novel by Torsten ...
;
Triton
Triton commonly refers to:
* Triton (mythology), a Greek god
* Triton (moon), a satellite of Neptune
Triton may also refer to:
Biology
* Triton cockatoo, a parrot
* Triton (gastropod), a group of sea snails
* ''Triton'', a synonym of ''Triturus'' ...
,;
Saturn moons – Titan and
Enceladus
Enceladus is the sixth-largest moon of Saturn (19th largest in the Solar System). It is about in diameter, about a tenth of that of Saturn's largest moon, Titan. Enceladus is mostly covered by fresh, clean ice, making it one of the most refle ...
; Uranus moons –
Miranda,
Umbriel,
Oberon
Oberon () is a king of the fairies in medieval and Renaissance literature. He is best known as a character in William Shakespeare's play ''A Midsummer Night's Dream'', in which he is King of the Fairies and spouse of Titania, Queen of the Fair ...
;
Kuiper belt
The Kuiper belt () is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 t ...
objects including
Pluto
Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest k ...
-
Charon
In Greek mythology, Charon or Kharon (; grc, Χάρων) is a psychopomp, the ferryman of Hades, the Greek underworld. He carries the souls of those who have been given funeral rites across the rivers Acheron and Styx, which separate the wo ...
system,
Haumea
, discoverer =
, discovered =
, earliest_precovery_date = March 22, 1955
, mpc_name = (136108) Haumea
, pronounced =
, adjectives = Haumean
, note = yes
, alt_names =
, named_after = Haumea
, mp_category =
, orbit_ref =
, epoch ...
,
28978 Ixion
28978 Ixion (, provisional designation ) is a large trans-Neptunian object and a possible dwarf planet. It is located in the Kuiper belt, a region of icy objects orbiting beyond Neptune in the outer Solar System. Ixion is classified as a plut ...
,
90482 Orcus
Orcus (minor-planet designation 90482 Orcus, provisional designation ) is a trans-Neptunian dwarf planet with a large moon, Vanth. It has a diameter of . The surface of Orcus is relatively bright with albedo reaching 23 percent, neutral in colo ...
,
50000 Quaoar
Quaoar (50000 Quaoar), provisional designation , is a dwarf planet in the Kuiper belt, a region of icy planetesimals beyond Neptune. A non-resonant object (cubewano), it measures approximately in diameter, about half the diameter of Pluto. The ...
*
Silicate rock – Mercury, Venus, Earth, Mars, asteroids,
Ganymede,
Callisto Callisto most commonly refers to:
* Callisto (mythology), a nymph
*Callisto (moon), a moon of Jupiter
Callisto may also refer to:
Art and entertainment
*'' Callisto series'', a sequence of novels by Lin Carter
*''Callisto'', a novel by Torsten ...
, Moon, Triton
*
Regolith
Regolith () is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestri ...
– Mercury; Venus,
Earth-Moon system; Mars (and its moons
Phobos
Phobos (Greek for "fear") most commonly refers to:
* Phobos (moon), a moon of Mars
* Phobos (mythology), the Greek god and personification of fear and panic
Phobos may also refer to:
Comics
* Phobos (Marvel Comics)
* Phobos (''W.I.T.C.H.''), a ...
and
Deimos Deimos, a Greek word for ''dread'', may refer to:
* Deimos (deity), one of the sons of Ares and Aphrodite in Greek mythology
* Deimos (moon), the smaller and outermost of Mars' two natural satellites
* Elecnor Deimos, a Spanish aerospace company
* ...
); asteroids (including
4 Vesta
Vesta ( minor-planet designation: 4 Vesta) is one of the largest objects in the asteroid belt, with a mean diameter of . It was discovered by the German astronomer Heinrich Wilhelm Matthias Olbers on 29 March 1807 and is named after Vesta, th ...
); Titan
*
Nitrogen ice
Solid nitrogen is a number of solid forms of the element nitrogen, first observed in 1884. Solid nitrogen is mainly the subject of academic research, but low-temperature, low-pressure solid nitrogen is a substantial component of bodies in the ou ...
() –
Pluto
Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest k ...
–Charon,
Triton
Triton commonly refers to:
* Triton (mythology), a Greek god
* Triton (moon), a satellite of Neptune
Triton may also refer to:
Biology
* Triton cockatoo, a parrot
* Triton (gastropod), a group of sea snails
* ''Triton'', a synonym of ''Triturus'' ...
,
Kuiper belt
The Kuiper belt () is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 t ...
objects,
Plutino
In astronomy, the plutinos are a dynamical group of trans-Neptunian objects that orbit in 2:3 mean-motion resonance with Neptune. This means that for every two orbits a plutino makes, Neptune orbits three times. The dwarf planet Pluto is th ...
s
*
Sulphur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
() – Mercury; Earth; Mars; Jupiter moons – Io and Europa
Rare inorganics
*
Salts
In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively ...
– Earth, Mars, Ceres, Europa and Jupiter Trojans, Enceladus
*
Clays
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4).
Clays develop plasticity when wet, due to a molecular film of water surrounding the clay part ...
– Earth; Mars; asteroids including Ceres and
Tempel 1
Tempel 1 (official designation: 9P/Tempel) is a periodic Jupiter-family comet discovered by Wilhelm Tempel in 1867. It completes an orbit of the Sun every 5.5 years. Tempel 1 was the target of the ''Deep Impact'' space mission, which photogra ...
;
Europa
*
Sand
Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a soil texture, textur ...
– Earth, Mars, Titan
*
Calcium carbonate () – Earth, Mars
[
]
*
Sodium carbonate () – Earth, Ceres
= Carbon Ices
=
*
Dry ice
Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily ...
() – Mars (polar); Ariel;
[
] Umbriel;
Titania;
Ganymede;
Callisto
*
Carbon monoxide
Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...
ice () - Triton
Landforms

Common surface features include:
*
Impact crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact crater ...
s (though rarer on bodies with thick atmospheres, the largest being
Hellas Planitia
Hellas Planitia is a plain located within the huge, roughly circular impact basin Hellas located in the southern hemisphere of the planet Mars. Hellas is the third- or fourth-largest known impact crater in the Solar System. The basin floor ...
on
Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin atmos ...
)
*
Dunes
A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, f ...
as found on Venus, Earth, Mars and Titan
*
volcanoes
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often found where tectonic plates a ...
and
cryovolcanoes
A cryovolcano (sometimes informally called an ice volcano) is a type of volcano that erupts volatiles such as water, ammonia or methane into an extremely cold environment that is at or below their freezing point. The process of formation is known ...
*
Rille
Rille (German for 'groove') is typically used to describe any of the long, narrow depressions in the surface of the Moon that resemble channels. The Latin term is ''rima'', plural ''rimae''. Typically, a rille can be several kilometers wi ...
s
*
Mountains
A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher t ...
(the highest being
Rheasilvia
Rheasilvia is the most prominent surface feature on the asteroid Vesta and is thought to be an impact crater. It is in diameter, which is 90% the diameter of Vesta itself, and is 95% the mean diameter of Vesta, . However, the mean is affect ...
on
4 Vesta
Vesta ( minor-planet designation: 4 Vesta) is one of the largest objects in the asteroid belt, with a mean diameter of . It was discovered by the German astronomer Heinrich Wilhelm Matthias Olbers on 29 March 1807 and is named after Vesta, th ...
)
*
Escarpment
An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations.
The terms ''scarp'' and ''scarp face'' are often used interchangeably with ''esca ...
s
* Canyons and
valley
A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over ...
s (the largest being
Valles Marineris
Valles Marineris (; Latin for '' Mariner Valleys'', named after the ''Mariner 9'' Mars orbiter of 1971–72 which discovered it) is a system of canyons that runs along the Martian surface east of the Tharsis region. At more than long, wide an ...
on Mars)
*
Cave
A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...
s
*
Lava tube
A lava tube, or pyroduct, is a natural conduit formed by flowing lava from a volcanic vent that moves beneath the hardened surface of a lava flow. If lava in the tube empties, it will leave a cave.
Formation
A lava tube is a type of lava ...
s, found on Venus, Earth, The Moon and Mars
Surface of gas giants
Normally,
gas giant
A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" ...
s are considered to not have a surface, although they might have a solid core of rock or various types of ice, or a liquid core of
metallic hydrogen
Metallic hydrogen is a phase of hydrogen in which it behaves like an electrical conductor. This phase was predicted in 1935 on theoretical grounds by Eugene Wigner and Hillard Bell Huntington.
At high pressure and temperatures, metallic hydro ...
. However, the core, if it exists, does not include enough of the planet's mass to be actually considered a surface. Some scientists consider the point at which the atmospheric pressure is equal to 1
bar
Bar or BAR may refer to:
Food and drink
* Bar (establishment), selling alcoholic beverages
* Candy bar
* Chocolate bar
Science and technology
* Bar (river morphology), a deposit of sediment
* Bar (tropical cyclone), a layer of cloud
* Bar (un ...
, equivalent to the atmospheric pressure at Earth's surface, to be the surface of the plane
Life
Planetary surfaces are investigated for the presence of past or present
extraterrestrial life.
Thomas Gold
Thomas Gold (May 22, 1920 – June 22, 2004) was an Austrian-born American astrophysicist, a professor of astronomy at Cornell University, a member of the U.S. National Academy of Sciences, and a Fellow of the Royal Society (London). Gold was ...
expanded the field by advancing the possibility of life and a so-called
deep biosphere
The deep biosphere is the part of the biosphere that resides below the first few meters of the surface. It extends down at least 5 kilometers below the continental surface and 10.5 kilometers below the sea surface, at temperatures that ...
below the surface of a celestial body, and not only on the surface.
Surface chauvinism and surfacism
Furthermore, Thomas Gold has criticized science which only focuses on the surface and not below in its search of life as ''surface chauvinism''.
Similarly the focus on surface bound and territorial
space advocacy
Space advocacy is supporting or advocating for a human use of outer space. Purposes advocated can reach from space exploration, or commercial use of space to even space settlement. There are many different individuals and organizations dedicate ...
, particularly for
space colonization
Space colonization (also called space settlement or extraterrestrial colonization) is the use of outer space or celestial bodies other than Earth for permanent habitation or as extraterrestrial territory.
The inhabitation and territor ...
such as
of Mars, has been named ''surfacism'', neglecting interest for atmospheres and potential atmospheric human habitation,
such as above the surface of Venus.
See also
*
Extraterrestrial atmosphere
The study of extraterrestrial atmospheres is an active field of research, both as an aspect of astronomy and to gain insight into Earth's atmosphere. In addition to Earth, many of the other astronomical objects in the Solar System have atmosphe ...
*
Hydrosphere
The hydrosphere () is the combined mass of water found on, under, and above the surface of a planet, minor planet, or natural satellite. Although Earth's hydrosphere has been around for about 4 billion years, it continues to change in shape. Thi ...
**
Subsurface ocean
Planetary oceanography also called exo-oceanography is the study of oceans on planets and moons other than Earth. Unlike other planetary sciences like astrobiology, astrochemistry and planetary geology, it only began after the discovery of undergr ...
**
Ocean world
An ocean world, ocean planet, panthalassic planet, maritime world, water world or aquaplanet, is a type of planet that contains a substantial amount of water in form of oceans, either beneath the surface, as subsurface oceans, or on the surfa ...
*
Planetary radius
A planetary coordinate system is a generalization of the geographic coordinate system and the geocentric coordinate system for planets other than Earth.
Similar coordinate systems are defined for other solid celestial bodies, such as in the ''selen ...
*
Planetary geoid
A planetary coordinate system is a generalization of the geographic coordinate system and the geocentric coordinate system for planets other than Earth.
Similar coordinate systems are defined for other solid celestial bodies, such as in the '' sel ...
References
{{reflist
, colwidth = 30em
, refs =
[
{{cite encyclopedia
, title = Encyclopedia of the Solar System
, chapter = Triton
, last1 = McKinnon
, first1 = William B.
, last2 = Kirk
, first2 = Randolph L.
, publisher = Academic Press
, date = 2007
, editor = Lucy Ann Adams McFadden
, editor2 = Lucy-Ann Adams
, editor3 = Paul Robert Weissman
, editor4 = Torrence V. Johnson
, edition = 2nd
, location = Amsterdam; Boston
, isbn = 978-0-12-088589-3
, pages ]
483–502
, chapter-url = https://archive.org/details/encyclopediaofso0000unse_u6d1/page/483
Planetary geology
Surfaces