Acidalia Planitia is a
plain
In geography, a plain, commonly known as flatland, 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 ...
on
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 ...
, 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 A ...
volcanic province and
Arabia Terra 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 than ...
, centered at .
[
] Most of this region is found in the
Mare Acidalium quadrangle
The Mare Acidalium quadrangle is one of a series of list of quadrangles on Mars, 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Quadrangle (geography), quadrangle is located in t ...
, but a small part is in the
Ismenius Lacus quadrangle
The Ismenius Lacus quadrangle is one of a series of list of quadrangles on Mars, 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Quadrangle (geography), quadrangle is located in th ...
. The plain contains the famous
Cydonia region at the contact with the heavily cratered highland terrain.
The plain is named after a corresponding
albedo feature
In planetary geology, 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 usu ...
on a map by
Giovanni Schiaparelli
Giovanni Virginio Schiaparelli ( , , ; 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, unde ...
, 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 is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...
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, the crystalline forms of silica (silicon dio ...
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 (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...
s.
Oceans
Utopia Planitia
Utopia Planitia ( Greek and Latin: "Utopia 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 t ...
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 fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...
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
image:PIA02040 Martian hemispheres by MOLA.jpg, 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 ...
(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 solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...
deposits, found on the planet of
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 ...
. They are named for their resemblance to terrestrial
gullies. First discovered on images from
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 ...
, 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
*Dendri ...
''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

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 Slurry, slurries, water and gases. Several geological processes may cause the formation of mud volcanoes. Mud volcanoes are not true Igneous rock, igneous volcanoes as th ...
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
An iron oxide is a chemical compound composed of iron and oxygen. Several iron oxides are recognized. Often they are nonstoichiometric, non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is ...
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, mutualistic, or pathogenic found in and on all multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found ...
.
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.
See also
*
Geography of Mars
Areography, also known as the geography of Mars, is a subfield of planetary science that entails the delineation and characterization of regions on Mars. Areography is mainly focused on what is called physical geography on Earth; that is the di ...
*
List of plains on Mars
*
Martian Gullies
Martian gullies are small, incised networks of narrow channels and their associated downslope sediment deposits, found on the planet of Mars. They are named for their resemblance to terrestrial gullies. First discovered on images from Mars Global ...
*
Martian North Polar Basin
References
External links
Google Mars zoomable map centered on Acidalia Planitia
{{Authority control
Plains on Mars
Mare Acidalium quadrangle
Ismenius Lacus quadrangle