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An albedo feature is a large area on the surface of a
USGS Astrologeology Program, Martian Nomenclature
Planetary science Planetary geology
An albedo feature is a large area on the surface of a planet
A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...
(or other 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 ...
body) which shows a contrast in brightness or darkness (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 ...
) with adjacent areas.
Historically, albedo features were the first (and usually only) features to be seen and named 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 at ...
and Mercury. Early classical maps (such as those of Schiaparelli and Antoniadi) showed only albedo features, and it was not until the arrival of 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 that other surface features such as craters could be seen.
On bodies other than Mars and Mercury, an albedo feature is sometimes called a regio.
On bodies with a very thick atmosphere like 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 ...
or Titan, permanent albedo features cannot be seen using ordinary optical telescopes because the surface is not visible, and only clouds and other transient atmospheric phenomena are seen. The '' Cassini–Huygens'' probe observed multiple albedo features on Titan after its arrival in Saturn's orbit in 2004.
The first albedo feature ever seen on another planet was Syrtis Major Planum on Mars in the 17th century.
Today, thanks to space probes, very high-resolution images of surface features on Mars and Mercury are available, and the classical nomenclature based on albedo features has fallen somewhat into disuse. Although it is still used for Earth-based observing of Mars by amateur astronomer
Amateur astronomy is a hobby where participants enjoy observing or imaging celestial objects in the sky using the unaided eye, binoculars, or telescopes. Even though scientific research may not be their primary goal, some amateur astronomers ...
s.
However, for some Solar System bodies (such as 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 ...
prior to the '' New Horizons'' mission), the best available images show only albedo features. These images were usually taken by the Hubble Space Telescope
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...
or by ground-based telescopes using adaptive optics
Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical tele ...
.
Cydonia Mensae on Mars is an example of an albedo feature.
See also
* Classical albedo features on Mars *List of albedo features on Mercury
This is a list of the albedo features of the planet Mercury as seen by early telescopic observation.
Early telescopic observations of Mercury were based on the assumption that Mercury keeps one of its faces permanently turned toward the Sun, th ...
* Massif
In geology, a massif ( or ) is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole. The term also refers to a ...
References
{{Reflist *''The Origins of Martian Nomenclature'', T. L. MacDonald, 1971. *''The Planet Mars: A History of Observation and Discovery'', William Sheehan.USGS Astrologeology Program, Martian Nomenclature
Planetary science Planetary geology