Distribution of dune fields in the Planum Boreum region

Siton Undae is one of the largest and densest

dune field 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 ...

s in the vicinity of

Planum Boreum Planum Boreum (Latin: "the northern plain") is the northern polar plain on Mars. It extends northward from roughly 80°N and is centered at . Surrounding the high polar plain is a flat and featureless lowland plain called Vastitas Borealis which e ...

, the

Martian Mars, the fourth planet from the Sun, has appeared as a setting in works of fiction since at least the mid-1600s. It became the most popular celestial object in fiction in the late 1800s as the Moon was evidently lifeless. At the time, the pre ...

northern polar ice-cap. It is named after one of the

classical albedo features on Mars The 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 fe ...

. Its name was officially approved by

IAU The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

on 20 March 2007. It extends from latitude 73.79°N to 77.5°N and from longitude 291.38°E to 301.4°E (43.98°W – 57.08°W). Its centre is located at latitude 75.55°N, longitude 297.28E (62.72°W), and has a diameter of . Siton Undae is part of a cluster of sand-seas (undae), which along with Hyperboreae, and

Abalos Undae Abalos Undae (Latin for "Abalos Waves") is a dune field on Mars in the periphery of Planum Boreum, the Martian North pole. It is one of the officially named northern circumpolar dune fields, along with Olympia, Hyperboreae, and Siton Undae, ...

, overlay the lowlands of

Vastitas Borealis (Latin 'northern waste') is the largest lowland region of Mars. It is in the northerly latitudes of the planet and encircles the northern polar region. Vastitas Borealis is often simply referred to as the northern plains, northern lowlands or ...

. Siton Undae superposes the deepest basin of the northern region of Mars and contains amorphous

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is o ...

-coated glass-rich dunes. It is theorised that the formation of Siton Undae may have occurred during early erosion incidents of the Planum Boreum cavi unit, and that Rupes Tenuis may also have been a sand source, although it is now depleted. Other dune fields sharing the same formation history include Olympia and

Aspledon Undae Aspledon Undae is one of the named northern circumpolar dune fields in the vicinity of Planum Boreum, the Martian North pole. It is named after one of the classical albedo features on Mars. Its name was officially approved by the International A ...

. Siton Undae is the southernmost of the densest northern circumpolar dune fields and its presence indicates effective sand transport and accumulation from sand sources to the north and west. Siton Undae, along with

Abalos Abalos is a surname. People with this surname include: * Benjamin Abalos (born 1935), Filipino politician * Benjamin Abalos Jr. (born 1962), Filipino politician and son of the above * Carmelita Abalos (born 1962), Filipino politician, wife of Benj ...

, and Hyperboreae Undae, is also a tributary to less dense dune fields that continue all the way to the Martian

prime meridian A prime meridian is an arbitrary meridian (a line of longitude) in a geographic coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its anti-meridian (the 180th meridian in a 360°-system) form a great ...

Dune characteristics

Spectral analysis of the dunes of the circumpolar

erg The erg is a unit of energy equal to 10−7joules (100 nJ). It originated in the Centimetre–gram–second system of units (CGS). It has the symbol ''erg''. The erg is not an SI unit. Its name is derived from (), a Greek word meaning 'work' o ...

s, including Siton Undae, using the OMEGA instrument on board the European

Mars Express ''Mars Express'' is a space exploration mission being conducted by the European Space Agency (ESA). The ''Mars Express'' mission is exploring the planet Mars, and is the first planetary mission attempted by the agency. "Express" originally ref ...

orbiter, indicates that 80 to 90 percent of these sands are composed of

volcanic glass Volcanic glass is the amorphous (uncrystallized) product of rapidly cooling magma. Like all types of glass, it is a state of matter intermediate between the closely packed, highly ordered array of a crystal and the highly disordered array of liqu ...

produced by eruptions of volcanoes situated in Martian glaciers. These ratios of glass and crystalline material are similar to those obtained in

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its ...

from eruptions of volcanoes below the ice. It is also theorised that significant amounts of granular glass may have been transferred to Vastitas Borealis, and Siton Undae, by catastrophic floods originating from

Chryse Planitia Chryse Planitia (Greek, "''Golden Plain''") is a smooth circular plain in the northern equatorial region of Mars close to the Tharsis region to the west, centered at . Chryse Planitia lies partially in the Lunae Palus quadrangle, partially in th ...

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 ...

Juventae Chasma Juventae Chasma is an enormous box canyon (250 km × 100 km) on Mars which opens to the north and forms the outflow channel Maja Valles. Juventae Chasma is located north of Valles Marineris in the Coprates quadrangle and cuts more than ...

, and the southern Acidalia region of Mars. The dunes of Siton Undae contain amorphous

-coated glass-rich sand. The lack of evidence for the presence of volcanoes in the region of Planum Boreum, as well as the absence of evidence of any large-scale melt deposits due to crater impact, suggests that these silica-coated deposits may have formed by alteration of the basaltic sands through acidic action. Further, it is theorised that acidic alteration of glassy deposits may have been a common conversion mechanism on Mars, especially at high latitudes.

Images from THEMIS

File:PIA18260 Siton Undae.jpg , Dunes of Siton Undae from NASA's

Thermal Emission Imaging System The Thermal Emission Imaging System (THEMIS) is a camera on board the 2001 Mars Odyssey orbiter. It images Mars in the visible and infrared parts of the electromagnetic spectrum in order to determine the thermal properties of the surface and t ...

(THEMIS) File:PIA20454 Siton Undae close up.jpg, Siton Undae close up from NASA's

(THEMIS)

References

{{Portal bar, Solar System Dunes on Mars Mare Boreum quadrangle

Dune characteristics

Images from THEMIS

See also

References