Ogygis Undae is the only named southern hemisphere

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, fl ...

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...

. 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 ...

, ''Ogygis Regio''. Its name, which refers to

Ogyges Ogyges, also spelled Ogygos or Ogygus (Ancient Greek: Ὠγύγης or Ὤγυγος), is a primeval mythological ruler in ancient Greece, generally of Boeotia, but an alternative tradition makes him the first king of Attica. Etymology Though the ...

, a primeval mythological ruler in

ancient Greece Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity ( AD 600), that comprised a loose collection of cult ...

, was officially approved by the

International Astronomical Union 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, outreac ...

(IAU) on September 17, 2015. It is situated just outside

Argyre Planitia Argyre Planitia is a plain located within the impact basin Argyre in the southern highlands of Mars. Its name comes from a map produced by Giovanni Schiaparelli in 1877; it refers to Argyre, a mythical island of silver in Greek mythology. Arg ...

, a plain located in the southern highlands of Mars. The dunes of Ogygis Undae extend from latitude −49.94°N to −49.37°N and from longitude 292.64°E to 294.93°E (65.07°W – 67.36°W). They are centered at latitude −49.66°N, longitude 293.79°E (66.21°W), and extend approximately 87 km to the east and west from there. Ogygis Undae has an area of 1904 km², and due to its large size is a primary subject for research on Martian

dune 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 ...

morphology and

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 textural class of s ...

composition.

Morphology

Ogygis Undae is the final sink of an extended sand transport system that was imaged with the HRSC camera onboard

ESA , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (1205 ...

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 ...

. The complexity of this transport system is as extensive as some terrestrial examples. Dunes in Ogygis Undae have several morphologies including: barhcan, barchanoid, dome and star dunes. The variety of dune types indicates that they were deposited in a multimodal wind regime with different winds converging into the basin where the dunes are located, carrying sand from multiple source areas. The morphological complexity is mirrored by the diverse mineral composition of the dune-forming sediment.

Composition

Mineral distribution across the dune fields of Ogygis Undae is non-uniform and bimodal. The relative juxtaposition of the two primary grain types reveals how

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 ...

affect the transport of sand on the surface of Mars. Compositional spectra were acquired and analyzed in 2016 by USGS scientists using both the

Thermal Emission Spectrometer The Thermal Emission Spectrometer (TES) is an instrument on board Mars Global Surveyor. TES collects two types of data, hyperspectral thermal infrared data from 6 to 50 micrometres (μm) and bolometric visible-NIR (0.3 to 2.9 μm) measurements. TE ...

(TES) instrument on board

Mars Global Surveyor ''Mars Global Surveyor'' (MGS) was an American robotic space probe developed by NASA's Jet Propulsion Laboratory and launched November 1996. MGS was a global mapping mission that examined the entire planet, from the ionosphere down through the a ...

and the

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 to ...

(THEMIS) on board the

2001 Mars Odyssey ''2001 Mars Odyssey'' is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectr ...

spacecraft. Other characteristics of Ogygis Undae, such as its nocturnal thermal inertia values, corroborate the finding that there is a bimodal sand-type distribution across the field.

Thermal emission spectroscopy Thermal infrared spectroscopy (TIR spectroscopy) is the subset of infrared spectroscopy that deals with radiation emitted in the infrared part of the electromagnetic spectrum. The emitted infrared radiation, though similar to blackbody radiation, ...

results from the large dune field located inside

Gale Crater Gale is a crater, and probable dry lake, at in the northwestern part of the Aeolis quadrangle on Mars. It is in diameter and estimated to be about 3.5–3.8 billion years old. The crater was named after Walter Frederick Gale, an amateur astr ...

were used as a reference for data obtained from Ogygis Undae because the features of Gale Crater were investigated extensively both by orbiting spacecraft and on site by the NASA Mars rover, ''

Curiosity Curiosity (from Latin '' cūriōsitās'', from ''cūriōsus'' "careful, diligent, curious", akin to ''cura'' "care") is a quality related to inquisitive thinking such as exploration, investigation, and learning, evident by observation in humans ...

'', a part of the

Mars Science Laboratory Mars Science Laboratory (MSL) is a robotic spacecraft, robotic space probe mission to Mars launched by NASA on November 26, 2011, which successfully landed ''Curiosity (rover), Curiosity'', a Mars rover, in Gale (crater), Gale Crater on August ...

(MSL) mission. Ogygis Undae differs from the Gale dune field in both sand-type composition and

homogeneity Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity of a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, siz ...

, indicating differences in both the types of sources for these dune fields as well as the distance from their respective sand-sources. The USGS investigators also noted that the dunes of Ogygis Undae look similar to the dunes in

Grand Falls, Arizona Grand Falls is a natural waterfall system located 30 miles (48.3 kilometers) northeast of Flagstaff, Arizona in the Painted Desert on the Navajo Nation. It is also called Chocolate Falls because of the color. At tall, it is taller than Niaga ...

References

{{Geography of Mars Dunes on Mars Thaumasia quadrangle

Morphology

Composition

See also

References