Acidalia Planitia is a

plain In geography, a plain is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and as plateaus or uplands ...

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 ...

, between the

Tharsis Tharsis () is a vast volcanic plateau centered near the equator in the western hemisphere of Mars. The region is home to the largest volcanoes in the Solar System, including the three enormous shield volcanoes Arsia Mons, Pavonis Mons, and Asc ...

volcanic province and

Arabia Terra Arabia Terra is a large upland region in the north of Mars that lies mostly in the Arabia quadrangle, but a small part is in the Mare Acidalium quadrangle. It is densely cratered and heavily eroded. This battered topography indicates great age, ...

to the north of

Valles Marineris Valles Marineris (; Latin for ''Mariner program, Mariner Valleys'', named after the ''Mariner 9'' Mars orbiter of 1971–72 which discovered it) is a system of canyons that runs along the Mars, Martian surface east of the Tharsis region. At more ...

, centered at . Most of this region is found in the

Mare Acidalium quadrangle The Mare Acidalium quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is located in the northeastern portion of Mars’ western hemisphere ...

, but a small part is in the

Ismenius Lacus quadrangle The Ismenius Lacus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is located in the northwestern portion of Mars’ eastern hemisphere ...

. The plain contains the famous

Cydonia Cydonia may refer to: Music * ''Cydonia'' (album), a 2001 album by The Orb * "Cydonia", a track by heavy metal band Crimson Glory from '' Astronomica'' Places and jurisdictions * Kydonia or Cydonia, an ancient city state on Crete, at modern ...

region at the contact with the heavily cratered highland terrain. The plain is named after a corresponding

albedo feature 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 first (and usually only) features to b ...

on a map by

Giovanni Schiaparelli Giovanni Virginio Schiaparelli ( , also , ; 14 March 1835 – 4 July 1910) was an Italian astronomer and science historian. Biography He studied at the University of Turin, graduating in 1854, and later did research at Berlin Observatory, ...

, which was in turn named after the mythological fountain of Acidalia. Some places in Acidalia Planitia show cones, which some researchers have suggested are mud volcanoes. The scientific community is divided over whether an ancient

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

existed on the plain and other parts of the northern lowlands.

Geological history

There are several hypotheses regarding the geological history of Acidalia Planitia based on evidence from satellite data.

Springs and steam vents

Acidalia Planitia was once covered by ancient crust. Its surface eroded into knobs of iron/magnesium

phyllosilicates Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...

during the Amazonian. Sediments filled the empty plain, leaving the phyllosilicate knobs as protrusions through the surface. The spatial density of these knobs is consistent with the ancient crust that was once above Acidalia Planitia. Hydrated silica materials surround the phyllosilicate knobs and the sides of rocky slopes. Rather than covering the entire surface, these features are localized. This indicates that the plain was once home to springs and steam vents not extensive bodies of water such as oceans or

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...

Oceans

Utopia Planitia Utopia Planitia (Greek and Latin: "Nowhere Land Plain") is a large plain within Utopia, the largest recognized impact basin on Mars and in the Solar System with an estimated diameter of . It is the Martian region where the ''Viking 2'' lander tou ...

is a similar plain at the same latitude as Acidalia Planitia. Etched flows in its terrain suggest that mud flowed into Utopia Planitia creating a large reservoir of water and mud in the deepest part of the basin, about 1000 km across. This may have been the remnants of a more extensive ocean that covered all of the northern lowlands including Acidalia Planitia. The Vastitas Borealis Formation (VBF) stretched across both Utopia and Acidalia Planitiae and delineated the threshold for an ancient ocean. The two segments of the VBF at Utopia and Acidalia have congruent ages, reliefs, crater frequencies,

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

s, thermal properties, and superpositions of geological features. This suggests that the Acidalia Planitia may have once been covered by a large Martian ocean.

Glaciers

Craters on Acidalia Planitia are asymmetrical.

Mars Orbital Laser Altimeter 260px, MOLA topographic images of the two hemispheres of Mars. This image appeared on the cover of ''Science'' magazine in May 1999. The Mars Orbiter Laser Altimeter (MOLA) was one of five instruments on the ''Mars Global Surveyor'' (MGS) spacecraf ...

(MOLA) data revealed that the slopes of the pole-facing crater walls are shallower than the equator-facing slopes. Other studies show the opposite asymmetry to be true. The two theories indicate either biased glacial deposition during the Amazonian era or long-term creep of hundreds of meters of ice-rich

regolith Regolith () is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestria ...

beneath the surface, respectively.

Geological features

Gullies

Martian gullies are small, incised networks of narrow channels and their associated downslope

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

deposits, found on the planet of

. They are named for their resemblance to terrestrial

gullies A gully is a landform created by running water, mass movement, or commonly a combination of both eroding sharply into soil or other relatively erodible material, typically on a hillside or in river floodplains or terraces. Gullies resemble lar ...

. First discovered on images from

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 ...

, they occur on steep slopes, especially on the walls of craters. Usually, each gully has a

dendritic Dendrite derives from the Greek word "dendron" meaning ( "tree-like"), and may refer to: Biology *Dendrite, a branched projection of a neuron *Dendrite (non-neuronal), branching projections of certain skin cells and immune cells Physical * Dendr ...

''alcove'' at its head, a fan-shaped ''apron'' at its base, and a single thread of incised ''channel'' linking the two, giving the whole gully an hourglass shape.Malin, M., Edgett, K. 2000. Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335. They are believed to be relatively young because they have few, if any craters. A subclass of gullies is also found cut into the faces of sand dunes which are themselves considered to be quite young. On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers believed that the processes carving the gullies involve liquid water. However, this remains a topic of active research.

Mud volcanoes

Possible_mud_volcano_on_Acidalia_Planitia_by_HiRISE

Cone-shaped features with higher albedo than surrounding rocks litter the surface of Acidalia Planitia. The most similar terrestrial feature to these formations are

mud volcano A mud volcano or mud dome is a landform created by the eruption of mud or slurries, water and gases. Several geological processes may cause the formation of mud volcanoes. Mud volcanoes are not true igneous volcanoes as they do not produce lava ...

es. On Mars, mud volcanoes have an average diameter of ~1 km and a relief of 10 to 180 meters. Their higher albedo is a result of more crystalline

iron oxides Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of which ...

than the rest of Acidalia Planitia. Mud volcanoes erupt sediments from deep beneath the surface and change the rising rocks very minimally. These rocks are used to analyze organic matter as mud volcanoes also create subterranean conduits for ancient ground water that may have hosted

microbiota Microbiota are the range of microorganisms that may be commensal, symbiotic, or pathogenic found in and on all multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found t ...

In popular culture

In the 2011 novel '' The Martian'' by Andy Weir, and its 2015 film adaptation, Acidalia Planitia is the landing site of the Ares III mission, where the protagonist is stranded following a dust storm.

Interactive Mars map

References

External links

Google Mars zoomable map centered on Acidalia Planitia
{{Authority control Plains on Mars Mare Acidalium quadrangle Ismenius Lacus quadrangle