Albedo feature
Encyclopedia
An albedo feature is a large area on the surface of a planet
(or other solar system
body) which shows a contrast in brightness or darkness (albedo
) with adjacent areas.
Historically, albedo features were the very first (and usually only) features to be seen and named on Mars
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
s that other surface features such as crater
s 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
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 very 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. It is however still used for Earth-based observing of Mars by amateur astronomer
s.
However, for some solar system bodies such as Pluto
and Ceres which have not been visited by space probes, the best available images show only albedo features. These images were usually taken by the Hubble Space Telescope
or by ground-based telescopes using adaptive optics
.
Cydonia Mensae on Mars is an example of an albedo feature.
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
(or other solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
body) which shows a contrast in brightness or darkness (albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
) with adjacent areas.
Historically, albedo features were the very first (and usually only) features to be seen and named on Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
and Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
. Early classical maps (such as those of Schiaparelli
Giovanni Schiaparelli
Giovanni Virginio Schiaparelli was an Italian astronomer and science historian. He studied at the University of Turin and Berlin Observatory. In 1859-1860 he worked in Pulkovo Observatory and then worked for over forty years at Brera Observatory...
and Antoniadi) showed only albedo features, and it was not until the arrival of space probe
Space probe
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...
s that other surface features such as 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...
s 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
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
or Titan
Titan (moon)
Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....
, 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 very 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. It is however still used for Earth-based observing of Mars by amateur astronomer
Amateur astronomy
Amateur astronomy, also called backyard astronomy and stargazing, is a hobby whose participants enjoy watching the night sky , and the plethora of objects found in it, mainly with portable telescopes and binoculars...
s.
However, for some solar system bodies such as Pluto
Pluto
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...
and Ceres which have not been visited by space probes, the best available images show only albedo features. These images were usually taken by the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
or by ground-based telescopes using adaptive optics
Adaptive optics
Adaptive optics is a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions. It is used in astronomical telescopes and laser communication systems to remove the effects of atmospheric distortion, and in retinal imaging systems to reduce the...
.
Cydonia Mensae on Mars is an example of an albedo feature.
See also
- List of albedo features on Mercury
- Classical albedo features on MarsClassical albedo features on MarsThe classical albedo features of Mars are the light and dark features that can be seen on the planet Mars through an Earth-based telescope. Before the age of space probes, several astronomers created maps of Mars on which they gave names to the features they could see. The most popular system of...
- MassifMassifIn geology, a massif 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...