Hesperia Planum
Encyclopedia
Hesperia Planum is a broad lava plain
in the southern highlands of the planet Mars
. The plain is notable for its moderate number of impact crater
s and abundant wrinkle ridges. It is also the location of the ancient volcano
Tyrrhena Mons (Tyrrhena Patera
). The Hesperian
time period on Mars is named after Hesperia Planum.
or classical antiquity
. Hesperia
is a Greco-Latin poetic term for “lands to the west,” which to the ancient Greeks
meant Italy
and to the Romans
, Spain
. Planum (pl. plana) is Latin
for plateau or high plain. It is a descriptor term used in planetary geology
for a relatively smooth, elevated terrain on another planet
or moon
.
The Hesperia region of Mars was named by Italian astronomer Giovanni Schiaparelli
in 1877 for an intermediate-toned albedo feature
centered at lat. 20°S, long. 240°W between two darker regions. Believing the dark areas were bodies of water, Schiaparelli interpreted Hesperia to be a floodplain
or marsh
bridging two adjacent seas, the Mare Tyrrhenum and Mare Cimmerium. Although the existence of seas on Mars had been discounted by the early 20th century, the true nature of the region remained obscure until the space age
. In 1972, the Mariner 9
spacecraft showed that Hesperia was a cratered, wind-streaked plain. The International Astronomical Union
(IAU) formally named the area Hesperia Planum in 1973. The dark areas flanking Hesperia Planum were found to be heavily cratered uplands. In 1979, the IAU designated the upland area to the west as Tyrrhena Terra
and to the east as Terra Cimmeria
. (Terra is a Latin descriptor term meaning land or continent.)
and is centered at lat. 22.3°S, long. 110°E in the Mare Tyrrhenum quadrangle
(MC-22). It has a maximum width of 1700 km (1056 mi) and covers an area of about 2 million km2 (772000 sq. mi).
At large scales (>100 m), Hesperia Planum appears smooth and level, having a relatively uniform surface elevation of 1.2 km above Mars datum. The plain's surface is 200–800 m lower in elevation than the surrounding uplands of Tyrrhena Terra and Terra Cimmeria and is slightly tilted to the south, with a mean regional slope of about 0.03°. In high-resolution images (<19 m/pixel), the surface of Hesperia Planum is dominated by dust and fine-grained deposits. Few boulders or bedrock outcrops are visible. Abundant, shallow craters filled with smooth, flat-lying deposits are common. No vents or volcanic constructs are identifiable, although small (<10s meters wide) channels are present.
, although layered volcaniclastic or lacustrine
(lake-bed) sediments cannot be ruled out. The lavas appear to partly fill a large, irregular topographic depression that existed in Noachian
times. The rims of pre-existing impact craters are still visible in places, indicating that the lava deposits are 250–500 m in thickness. The volume of lavas within Hesperia Planum is comparable to that found in large igneous province
s on Earth, such as the Columbia River Basalt Group
.
, the number density of impact craters is a measure of the relative age
of a planetary surface. Heavily cratered surfaces are old, and sparsely cratered surfaces are young. Hesperia Planum is the type locality
for the Hesperian
System and time period. The lavas making up Hesperia Planum define the base of the Hesperian System. They erupted at the beginning of the Hesperian Period around 3700 million years ago. (Mars itself, along with the other planets, formed about 4500 million years ago.) Hesperian lavas are younger than the rocks in the heavily cratered Noachian
terrains but older than rocks formed during the more recent Amazonian Period. (See Geology of Mars.)
highs with a distinctive morphology that consists of a low, broad arch topped by a narrow crenulated ridge (pictured left). They are common features on the Moon where they occur exclusively within lava flow plains (the lunar maria
). Their occurrence on Mars is thought to reflect a similar volcanic association. Thus, areas on Mars with abundant wrinkle ridges are interpreted as plains formed by very fluid basaltic lava (flood basalt
s). The ridges themselves are believed to be the surface expression of thrust fault
s formed after the lava flows were emplaced. They are not volcanic features, but secondary, tectonic
structures that form in dense, competent rocks (such as layered basalts) that have undergone compressional stress. Hesperian-aged "ridged plains" like Hesperia Planum cover about 30% of the Martian surface.
) is an eroded, low-lying volcano in the western part of Hesperia Planum. It is one of the oldest large central-vent volcanoes on the planet and a member of a class of volcanoes called highland paterae, which erupted mainly in the Late Noachian
and Early Hesperian
. Tyrrhena Mons stands only 1.5 km above the surrounding plains. At its center lies a 40 km diameter depression, or caldera
, from which radiate numerous flat-floored valleys and ridges that suggest the volcano has been highly eroded. The low relief of Tyrrhena Mons combined with its degraded state indicate the volcano consists largely of friable and easily eroded material such as volcanic ash
. The ash was likely derived from the interaction of magma
with groundwater
or ice.
Lava plain
A lava plain, also called a lava field or lava bed, is a large expanse of nearly flat-lying lava flows. Such features are generally composed of highly-fluid basalt lava, and can extend for tens or even hundreds of miles across the underlying terrain...
in the southern highlands of the planet Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
. The plain is notable for its moderate number of impact crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
s and abundant wrinkle ridges. It is also the location of the ancient volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
Tyrrhena Mons (Tyrrhena Patera
Tyrrhena Patera
Tyrrhena Patera is the central depression of a large volcano in the Mare Tyrrhenum quadrangle of Mars, located at 21.36° south latitude and 253.47° west longitude. It was named after a classical albedo feature name. Pit chains are found at the summit of Tyrrhena Patera. They are formed by...
). The Hesperian
Hesperian
The Hesperian is a geologic system and time period on the planet Mars characterized by widespread volcanic activity and catastrophic flooding that carved immense outflow channels across the surface. The Hesperian is an intermediate and transitional period of Martian history...
time period on Mars is named after Hesperia Planum.
Name origin
Most place names on Mars are derived from sources in the BibleBible
The Bible refers to any one of the collections of the primary religious texts of Judaism and Christianity. There is no common version of the Bible, as the individual books , their contents and their order vary among denominations...
or classical antiquity
Classical antiquity
Classical antiquity is a broad term for a long period of cultural history centered on the Mediterranean Sea, comprising the interlocking civilizations of ancient Greece and ancient Rome, collectively known as the Greco-Roman world...
. Hesperia
Hesperia
Hesperia may refer to:Hesperia or Hesper is the Greek goddess of the evening star in Greek mythology,may refer to:* Hesperia, one of the Hesperides in Greek mythology...
is a Greco-Latin poetic term for “lands to the west,” which to the ancient Greeks
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
meant Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
and to the Romans
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....
, Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
. Planum (pl. plana) is Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
for plateau or high plain. It is a descriptor term used in planetary geology
Planetary geology
Planetary geology, alternatively known as astrogeology or exogeology, is a planetary science discipline concerned with the geology of the celestial bodies such as the planets and their moons, asteroids, comets, and meteorites...
for a relatively smooth, elevated terrain on another planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
or moon
Natural satellite
A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called its primary. The two terms are used synonymously for non-artificial satellites of planets, of dwarf planets, and of minor planets....
.
The Hesperia region of Mars was named by Italian astronomer Giovanni Schiaparelli
Giovanni Schiaparelli
Giovanni Virginio Schiaparelli was an Italian astronomer and science historian. He studied at the University of Turin and Berlin Observatory. In 1859-1860 he worked in Pulkovo Observatory and then worked for over forty years at Brera Observatory...
in 1877 for an intermediate-toned albedo feature
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 features they could see. The most popular system of...
centered at lat. 20°S, long. 240°W between two darker regions. Believing the dark areas were bodies of water, Schiaparelli interpreted Hesperia to be a floodplain
Floodplain
A floodplain, or flood plain, is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge...
or marsh
Marsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....
bridging two adjacent seas, the Mare Tyrrhenum and Mare Cimmerium. Although the existence of seas on Mars had been discounted by the early 20th century, the true nature of the region remained obscure until the space age
Space Age
The Space Age is a time period encompassing the activities related to the Space Race, space exploration, space technology, and the cultural developments influenced by these events. The Space Age is generally considered to have begun with Sputnik...
. In 1972, the Mariner 9
Mariner 9
Mariner 9 was a NASA space orbiter that helped in the exploration of Mars and was part of the Mariner program. Mariner 9 was launched toward Mars on May 30, 1971 from Cape Canaveral Air Force Station and reached the planet on November 13 of the same year, becoming the first spacecraft to orbit...
spacecraft showed that Hesperia was a cratered, wind-streaked plain. The International Astronomical Union
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
(IAU) formally named the area Hesperia Planum in 1973. The dark areas flanking Hesperia Planum were found to be heavily cratered uplands. In 1979, the IAU designated the upland area to the west as Tyrrhena Terra
Tyrrhena Terra
Tyrrhena Terra is a large area on Mars, centered south of the Martian equator and immediately northeast of the Hellas basin. Its coordinates are , and it covers 2300 km at its broadest extent. It was named for a classic albedo feature of the planet and is in the Mare Tyrrhenum quadrangle of Mars...
and to the east as Terra Cimmeria
Terra Cimmeria
Terra Cimmeria is a large Martian region, centered at and covering 5400 km at its broadest extent. It covers latitudes 15 N to 75 S and longitudes 170 to 260 W. Terra Cimmeria is one part of the heavily cratered, southern highland region of the planet...
. (Terra is a Latin descriptor term meaning land or continent.)
Location and physical description
Hesperia Planum is located along the broad northeastern rim of the giant Hellas impact basinHellas Planitia
Hellas Planitia, also known as the Hellas Impact Basin, is a huge, roughly circular impact basin located in the southern hemisphere of the planet Mars. It is the second or third largest impact crater and the largest visible impact crater known in the Solar System...
and is centered at lat. 22.3°S, long. 110°E in the Mare Tyrrhenum quadrangle
Mare Tyrrhenum quadrangle
The Mare Tyrrhenum quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey Astrogeology Research Program. The Mare Tyrrhenum quadrangle is also referred to as MC-22 ....
(MC-22). It has a maximum width of 1700 km (1056 mi) and covers an area of about 2 million km2 (772000 sq. mi).
At large scales (>100 m), Hesperia Planum appears smooth and level, having a relatively uniform surface elevation of 1.2 km above Mars datum. The plain's surface is 200–800 m lower in elevation than the surrounding uplands of Tyrrhena Terra and Terra Cimmeria and is slightly tilted to the south, with a mean regional slope of about 0.03°. In high-resolution images (<19 m/pixel), the surface of Hesperia Planum is dominated by dust and fine-grained deposits. Few boulders or bedrock outcrops are visible. Abundant, shallow craters filled with smooth, flat-lying deposits are common. No vents or volcanic constructs are identifiable, although small (<10s meters wide) channels are present.
Geology
Hesperia Planum is generally interpreted to be composed of flood lavasFlood basalt
A flood basalt or trap basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalts have occurred on continental scales in prehistory, creating great plateaus and mountain ranges...
, although layered volcaniclastic or lacustrine
Lacustrine
Lacustrine means "of a lake" or "relating to a lake".Specifically, it may refer to:*Lacustrine plain*Lacustrine delta-Fish:*Lacustrine goby , a type of small fish found in Philippine waters belonging to the Gobiidae family, known in Tagalog as dulong-See also:*Fluvial - of or relating a...
(lake-bed) sediments cannot be ruled out. The lavas appear to partly fill a large, irregular topographic depression that existed in Noachian
Noachian
The Noachian is a geologic system and early time period on the planet Mars characterized by high rates of meteorite and asteroid impacts and the presence of abundant surface water...
times. The rims of pre-existing impact craters are still visible in places, indicating that the lava deposits are 250–500 m in thickness. The volume of lavas within Hesperia Planum is comparable to that found in large igneous province
Large igneous province
A Large Igneous Province is an extremely large accumulation of igneous rocks—intrusive, extrusive, or both—in the earth's crust...
s on Earth, such as the Columbia River Basalt Group
Columbia River Basalt Group
The Columbia River Basalt Group is a large igneous province that lies across parts of the Western United States. It is found in the U.S. states of Washington, Oregon, Idaho, Nevada, and California...
.
Impact cratering and age
The moderate amount of cratering on Hesperia Planum indicates that the plain has an intermediate age in Martian history. In planetary geologyPlanetary geology
Planetary geology, alternatively known as astrogeology or exogeology, is a planetary science discipline concerned with the geology of the celestial bodies such as the planets and their moons, asteroids, comets, and meteorites...
, the number density of impact craters is a measure of the relative age
Relative dating
Relative dating is the science determining the relative order of past events, without necessarily determining their absolute age.In geology rock or superficial deposits, fossils and lithologies can be used to correlate one stratigraphic column with another...
of a planetary surface. Heavily cratered surfaces are old, and sparsely cratered surfaces are young. Hesperia Planum is the type locality
Type locality (geology)
Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....
for the Hesperian
Hesperian
The Hesperian is a geologic system and time period on the planet Mars characterized by widespread volcanic activity and catastrophic flooding that carved immense outflow channels across the surface. The Hesperian is an intermediate and transitional period of Martian history...
System and time period. The lavas making up Hesperia Planum define the base of the Hesperian System. They erupted at the beginning of the Hesperian Period around 3700 million years ago. (Mars itself, along with the other planets, formed about 4500 million years ago.) Hesperian lavas are younger than the rocks in the heavily cratered Noachian
Noachian
The Noachian is a geologic system and early time period on the planet Mars characterized by high rates of meteorite and asteroid impacts and the presence of abundant surface water...
terrains but older than rocks formed during the more recent Amazonian Period. (See Geology of Mars.)
Wrinkle ridges
Wrinkle ridges are long, linear topographicTopography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
highs with a distinctive morphology that consists of a low, broad arch topped by a narrow crenulated ridge (pictured left). They are common features on the Moon where they occur exclusively within lava flow plains (the lunar maria
Maria
Maria is a female given name in many diverse cultures, including Mexican, African, Arab, Armenian, Bulgarian, Catalan, Croatian, English, Finnish, German, Greek, Italian, Maltese, Norwegian, Polish, Portuguese, Russian, Romanian, Pakistani, Afghan, Serbian, Swedish, Spanish.In Roman Empire the...
). Their occurrence on Mars is thought to reflect a similar volcanic association. Thus, areas on Mars with abundant wrinkle ridges are interpreted as plains formed by very fluid basaltic lava (flood basalt
Flood basalt
A flood basalt or trap basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalts have occurred on continental scales in prehistory, creating great plateaus and mountain ranges...
s). The ridges themselves are believed to be the surface expression of thrust fault
Thrust fault
A thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. They are often recognized because they place older rocks above younger...
s formed after the lava flows were emplaced. They are not volcanic features, but secondary, tectonic
Tectonics
Tectonics is a field of study within geology concerned generally with the structures within the lithosphere of the Earth and particularly with the forces and movements that have operated in a region to create these structures.Tectonics is concerned with the orogenies and tectonic development of...
structures that form in dense, competent rocks (such as layered basalts) that have undergone compressional stress. Hesperian-aged "ridged plains" like Hesperia Planum cover about 30% of the Martian surface.
Tyrrhena Mons
Tyrrhena Mons (Tyrrhena PateraTyrrhena Patera
Tyrrhena Patera is the central depression of a large volcano in the Mare Tyrrhenum quadrangle of Mars, located at 21.36° south latitude and 253.47° west longitude. It was named after a classical albedo feature name. Pit chains are found at the summit of Tyrrhena Patera. They are formed by...
) is an eroded, low-lying volcano in the western part of Hesperia Planum. It is one of the oldest large central-vent volcanoes on the planet and a member of a class of volcanoes called highland paterae, which erupted mainly in the Late Noachian
Noachian
The Noachian is a geologic system and early time period on the planet Mars characterized by high rates of meteorite and asteroid impacts and the presence of abundant surface water...
and Early Hesperian
Hesperian
The Hesperian is a geologic system and time period on the planet Mars characterized by widespread volcanic activity and catastrophic flooding that carved immense outflow channels across the surface. The Hesperian is an intermediate and transitional period of Martian history...
. Tyrrhena Mons stands only 1.5 km above the surrounding plains. At its center lies a 40 km diameter depression, or caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
, from which radiate numerous flat-floored valleys and ridges that suggest the volcano has been highly eroded. The low relief of Tyrrhena Mons combined with its degraded state indicate the volcano consists largely of friable and easily eroded material such as volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
. The ash was likely derived from the interaction of magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
with groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
or ice.