Arcadia Planitia
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Arcadia Planitia is a smooth plain with fresh lava flows and Amazonian volcanic flows 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 ...
. It was named by Giovanni Schiaparelli in 1882 after the Arcadia region of ancient
Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...
. It dates from the
Amazonian period The geological history of Mars follows the physical evolution of Mars as substantiated by observations, indirect and direct measurements, and various inference techniques. Methods dating back to 17th-century techniques developed by Nicholas Sten ...
's arcadia formation's
lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...
s and small
cinder cone A cinder cone or scoria cone is a steep, volcanic cone, conical landform of loose pyroclastic rock, pyroclastic fragments, such as volcanic ash, clinkers, or scoria that has been built around a volcanic vent. The pyroclastic fragments are forme ...
s. It includes a more recently developed large region of aeolian materials derived from periglacial processes. It is located northwest of the Tharsis region in the northern lowlands, spanning roughly the region 33.9–64.2° North and 165.9–210.4° East, straddling partly in the Cebrenia quadrangle (MC-07), and partly in the Diacria one (MC-02), and centered at . Arcadia marks a transition from the thinly cratered terrain to its north and the very old cratered terrain to the south. On its east it runs into the
Alba Mons Alba Mons (formerly and still occasionally known as Alba Patera, a term that has since been restricted to the volcano's summit caldera; also initially known as the Arcadia ring) is a volcano located in the northern Tharsis region of the planet Ma ...
volcanoes. Its elevation relative to the
geodetic datum A geodetic datum or geodetic system (also: geodetic reference datum, geodetic reference system, or geodetic reference frame, or terrestrial reference frame) is a global datum reference or reference frame for unambiguously representing the positi ...
varies between 0 and -3 km. Many low-lying areas of Arcadia are marked by grooves and sub-parallel ridges. These features indicate glaciation and appear similar to those on Earth, where the freezing and thawing of water located between ground layers contributes to the slow flow of near-surface materials. This supports the proposition that ground ice exists in the near-surface of Arcadia Planitia, and therefore this location is an area of interest for potential exploration missions.


Expanded craters

Large impacts often create swarms of small secondary craters from the debris that is blasted out as a consequence of the impact. Studies of a type of secondary craters, called expanded craters, have given us insights into places where abundant ice may be present in the ground. Expanded craters have lost their rims, which may be because any rim that was once present has collapsed into the crater during expansion or lost its ice if composed of ice. Excess ice (ice in addition to what is in the pores of the ground) is widespread throughout the Martian mid-latitudes, especially in Arcadia Planitia. In this region are many expanded secondary craters that probably form from impacts that destabilize a subsurface layer of excess ice, which subsequently sublimates. With sublimation, the ice changes directly from a solid to gaseous form. In the impact, the excess ice is broken up, resulting in an increase in surface area. Ice will sublimate much more if there is more surface area. After the ice disappears into the atmosphere, dry soil material will collapse and cause the crater diameter to become larger.Viola, D., et al. 2014. EXPANDED CRATERS IN ARCADIA PLANITIA: EVIDENCE FOR >20 MYR OLD SUBSURFACE ICE. Eighth International Conference on Mars (2014). 1022pdf. Places on Mars that display expanded craters may indicate where future colonists can find water ice. ESP 028411 2330expandedcraters.jpg, Close view of expanded craters, as seen by HiRISE. After the impact, ice left the ground and widened the crater's diameter.


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 ''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 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. The pictures below show gullies in Arcadia Planitia.


See also

* Climate of Mars *
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


References


External links


Google Mars zoomable map centered on Arcadia Planitia
{{Authority control Plains on Mars Cebrenia quadrangle Diacria quadrangle