Sotra Facula
Encyclopedia
Sotra Facula
(named after the Sotra
islands in Norway
) is a prominent feature on Titan
, the largest moon of Saturn
. It is believed to be an ice volcano or cryovolcano
, forming a roughly circular mountain measuring about 65 kilometres (40.4 mi) across. It has two peaks standing about 1000 metres (3,280.8 ft) and 1500 metres (4,921.3 ft) high with multiple craters as much as 1500 metres (4,921.3 ft) deep. Finger-like flows are visible on the flanks of the mountain, measuring perhaps 100 metres (328.1 ft) thick.
The Cassini–Huygens mission has mapped Sotra Facula using the Cassini orbiter's onboard radar instrument and the visual and infrared mapping spectrometer. An earlier survey of the region in 2004 revealed a circular bright spot, or facula, which was nicknamed "The Rose". A subsequent flyby by Cassini re-surveyed the region from a different angle, enabling members of the US Geological Survey Astrogeology Science Center to generate stereoscopic mapping of Sotra Facula and the surrounding area. Researchers also discovered at least two more mountains and another big crater, forming a chain of mountains several hundred kilometers long flanked by lava-covered lowlands.
Sotra Facula is regarded as "the very best evidence, by far, for volcanic topography anywhere documented on an icy satellite", according to planetary scientist Jeffrey Kargel of the University of Arizona
. It has been compared with terrestrial volcanoes such as Etna, Laki
and volcanic cones near Flagstaff, Arizona
. There is as yet no evidence of current activity, but researchers plan to monitor the area for changes.
It is unclear what might have been erupted from Sotra Facula—possibly water mixed with ammonium
, or more exotic hydrocarbon
compounds such as polyethylene
, paraffin waxes or asphalt
. The eruptions may also have brought methane
to the surface. Titan's dense methane atmosphere is constantly being broken down by sunlight in the upper atmosphere through photolysis; cryovolcanism may therefore explain how the atmosphere is being replenished.
The eruptions of Sotra Facula are presumed to originate in a layer of liquid water lying below Titan's icy crust. The mountain's heavily cratered appearance indicates that it must have erupted with considerable force, but the precise mechanism by which this happened is not certain. Liquid water is ordinarily denser than ice but it is possible that the water's density may be reduced by mixing with other substances, such as ammonia
, allowing it to force its way to the surface. Alternatively, some other mechanism such as the underground formation of methane bubbles or a build-up of tectonic pressure may be responsible.
Facula
A facula , Latin for "little torch", is literally a "bright spot." It is used in planetary nomenclature for naming certain surface features of planets and moons, and is also a type of surface phenomenon on the Sun....
(named after the Sotra
Sotra
Sotra is the name of an archipelago in Hordaland, Norway, just west of Bergen. The largest island is Store Sotra, while the second-largest and most populated is Litlesotra. The latter and part of Store Sotra are part of Fjell, while southern Sotra is part of Sund. Roughly 25,000 people live on Sotra...
islands in Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
) is a prominent feature on 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....
, the largest moon of Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
. It is believed to be an ice volcano or cryovolcano
Cryovolcano
A cryovolcano is a volcano that erupts volatiles such as water, ammonia or methane, instead of molten rock. Collectively referred to as cryomagma or ice-volcanic melt, these substances are usually liquids and form plumes, but can also be in vapour form...
, forming a roughly circular mountain measuring about 65 kilometres (40.4 mi) across. It has two peaks standing about 1000 metres (3,280.8 ft) and 1500 metres (4,921.3 ft) high with multiple craters as much as 1500 metres (4,921.3 ft) deep. Finger-like flows are visible on the flanks of the mountain, measuring perhaps 100 metres (328.1 ft) thick.
The Cassini–Huygens mission has mapped Sotra Facula using the Cassini orbiter's onboard radar instrument and the visual and infrared mapping spectrometer. An earlier survey of the region in 2004 revealed a circular bright spot, or facula, which was nicknamed "The Rose". A subsequent flyby by Cassini re-surveyed the region from a different angle, enabling members of the US Geological Survey Astrogeology Science Center to generate stereoscopic mapping of Sotra Facula and the surrounding area. Researchers also discovered at least two more mountains and another big crater, forming a chain of mountains several hundred kilometers long flanked by lava-covered lowlands.
Sotra Facula is regarded as "the very best evidence, by far, for volcanic topography anywhere documented on an icy satellite", according to planetary scientist Jeffrey Kargel of the University of Arizona
University of Arizona
The University of Arizona is a land-grant and space-grant public institution of higher education and research located in Tucson, Arizona, United States. The University of Arizona was the first university in the state of Arizona, founded in 1885...
. It has been compared with terrestrial volcanoes such as Etna, Laki
Laki
Łąki may refer to the following places in Poland:*Łąki, Lower Silesian Voivodeship *Łąki, West Pomeranian Voivodeship *Łąki, Lublin Voivodeship...
and volcanic cones near Flagstaff, Arizona
Flagstaff, Arizona
Flagstaff is a city located in northern Arizona, in the southwestern United States. In 2010, the city's population was 65,870. The population of the Metropolitan Statistical Area was at 134,421 in 2010. It is the county seat of Coconino County...
. There is as yet no evidence of current activity, but researchers plan to monitor the area for changes.
It is unclear what might have been erupted from Sotra Facula—possibly water mixed with ammonium
Ammonium
The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...
, or more exotic hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
compounds such as polyethylene
Polyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
, paraffin waxes or asphalt
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...
. The eruptions may also have brought methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
to the surface. Titan's dense methane atmosphere is constantly being broken down by sunlight in the upper atmosphere through photolysis; cryovolcanism may therefore explain how the atmosphere is being replenished.
The eruptions of Sotra Facula are presumed to originate in a layer of liquid water lying below Titan's icy crust. The mountain's heavily cratered appearance indicates that it must have erupted with considerable force, but the precise mechanism by which this happened is not certain. Liquid water is ordinarily denser than ice but it is possible that the water's density may be reduced by mixing with other substances, such as ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
, allowing it to force its way to the surface. Alternatively, some other mechanism such as the underground formation of methane bubbles or a build-up of tectonic pressure may be responsible.
External links
- "Sotra Facula". Gazetteer of Planetary Nomenclature, International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN).