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, flat ...

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

. 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 Ogygus (Ancient Greek: ), 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 original etymology and meaning are "un ...

, a primeval mythological ruler in

ancient Greece Ancient Greece () was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity (), that comprised a loose collection of culturally and linguistically r ...

, was officially approved by the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

(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. A ...

, 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, flat ...

morphology and

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...

composition.

Morphology

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

HRSC High Resolution Stereo Camera (HRSC) is a camera experiment on ''Mars Express''.DLR ...

camera onboard

ESA The European Space Agency (ESA) is a 23-member international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 in the context of European ...

Mars Express ''Mars Express'' is a space exploration mission by the European Space Agency, European Space Agency (ESA) exploring the planet Mars and its moons since 2003, and the first planetary mission attempted by ESA. ''Mars Express'' consisted of two ...

. 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 erosion, erode, transport, and deposit ...

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) was an instrument on board Mars Global Surveyor. TES collected two types of data, hyperspectral thermal infrared data from 6 to 50 micrometres (μm) and bolometric visible-near infrared (0.3 to 2.9 μm) me ...

(TES) instrument on board

Mars Global Surveyor ''Mars Global Surveyor'' (MGS) was an American Robotic spacecraft, robotic space probe developed by NASA's Jet Propulsion Laboratory. It launched November 1996 and collected data from 1997 to 2006. MGS was a global mapping mission that examined ...

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 spectro ...

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 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 a ...

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 , from "careful, diligent, curious", akin to "care") is a quality related to inquisitive thinking, such as exploration, investigation, and learning, evident in humans and other animals. Curiosity helps Developmental psyc ...

'', 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 Augus ...

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

homogeneity Homogeneity and heterogeneity are concepts relating to the Uniformity (chemistry), uniformity of a Chemical substance, substance, process or image. A homogeneous feature is uniform in composition or character (i.e., color, shape, size, weight, ...

, 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.

References

{{Geography of Mars Dunes on Mars Thaumasia quadrangle

Morphology

Composition

See also

References