Lineated valley fill
Encyclopedia
Lineated valley fill also called lineated floor deposit, is a feature of the floors of some channels on Mars
, exhibiting ridges and grooves that seem to flow around obstacles. Shadow measurements show that at least some of the ridges are several metres high. LVF is believed to be ice-rich. Hundreds of meters of ice probably lie protected in LVF under a thin layer of debris. The debris consists of wind-borne dust, material from alcove walls, and lag material remaining after ice sublimated (changed from a solid directly to a gas) from a rock-ice mixture. Some glacier
s on Earth show similar ridges.
Lineated floor deposits began as lobate debris apron
s (LDAs), which form as material leaves narrow mountain valleys and spreads out as an apron. By tracing the paths of the ridges on LDAs, researchers have come to believe that the curved ridges characteristic of lobate debris aprons straighten out to form the more or less straight ridges of LVF.
The same regions on Mars that host LVF and LDAs have concentric crater fill in many craters. Concentric Crater Fill
contains large ridges and other surfaces nicknamed brain terrain, after the surface corrugations of the human brain.
The study of lineated valley fill and other features related to debris-covered ice has been greatly aided by the abundance of data received from Mars orbiting instruments. Excellent images have been obtained from THEMIS
, MOC
, CTX
, and HiRISE
. Detailed altimetry was collected by MOLA
.
The Mars Reconnaissance Orbiter
's Shallow Radar gave a strong reflection from the top and base of LDAs, meaning that pure water ice made up the bulk of the formation (between the two reflections), strong evidence that the LDAs in Hellas Planitia
are glaciers covered with a thin layer of rocks. Since lineated valley terrain is derived from lobate debris aprons, it probably contains buried ice—at least in places.
. Earth's rather large moon prevents large changes in its tilt. The two moons of Mars are tiny. So Mars undergoes large periods when its ice cap receives more direct sunlight.
During this time ice in the cap sublimates, and thick snow falls in mid-latitudes — the zones where concentric crater fill, lineated valley fill and lobate debris aprons are common. The distribution of craters on LVF indicates a late Amazonian age for at least some areas.
boundary. The Nilosyrtis Mensae
, Protonilus Mensae
and Deuteronilus Mensae
bear many examples of LVF. Ismenius Lacus quadrangle and Hellas quadrangle contain many valleys displaying lineated valley fill.
LVF and other ice-related forms are collectively known as fretted terrain
, which includes winding and straight valleys with isolating plateaus and mesas.
has undergone many large changes in the past.
At times there is snow, and at times the snow may melt. The resulting small areas of liquid water cause weathering of the rocks and may provide a favourable environment for life. Understanding lineated valley fill and other manifestations of buried ice will allow future colonists to find sources of water
.
Reull Vallis
, as pictured below, displays such deposits. Sometimes the lineated floor deposits show a chevron pattern which is further evidence of movement. The picture below taken with HiRISE of Reull Vallis shows these patterns.
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...
, exhibiting ridges and grooves that seem to flow around obstacles. Shadow measurements show that at least some of the ridges are several metres high. LVF is believed to be ice-rich. Hundreds of meters of ice probably lie protected in LVF under a thin layer of debris. The debris consists of wind-borne dust, material from alcove walls, and lag material remaining after ice sublimated (changed from a solid directly to a gas) from a rock-ice mixture. Some glacier
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
s on Earth show similar ridges.
Lineated floor deposits began as lobate debris apron
Lobate Debris Apron
Lobate debris aprons are geological features on Mars, first seen by the Viking Orbiters, consisting of piles of rock debris below cliffs. These features have a convex topography and a gentle slope from cliffs or escarpments, which suggest flow away from the steep source cliff...
s (LDAs), which form as material leaves narrow mountain valleys and spreads out as an apron. By tracing the paths of the ridges on LDAs, researchers have come to believe that the curved ridges characteristic of lobate debris aprons straighten out to form the more or less straight ridges of LVF.
The same regions on Mars that host LVF and LDAs have concentric crater fill in many craters. Concentric Crater Fill
Concentric crater fill
Concentric crater fill is when the floor of a crater is mostly covered with a large number of parallel ridges. It is common in the mid-latitudes of Mars, and is widely believed to be caused by glacial movement...
contains large ridges and other surfaces nicknamed brain terrain, after the surface corrugations of the human brain.
The study of lineated valley fill and other features related to debris-covered ice has been greatly aided by the abundance of data received from Mars orbiting instruments. Excellent images have been obtained from THEMIS
Themis
Themis is an ancient Greek Titaness. She is described as "of good counsel", and is the embodiment of divine order, law, and custom. Themis means "divine law" rather than human ordinance, literally "that which is put in place", from the verb τίθημι, títhēmi, "to put"...
, MOC
MOC
-Computing:* Meta Object Compiler, used by the Qt development framework* Microsoft Office Communicator, instant messaging software* Music on Console, console audio player* Model of computation-Military:* Military occupation...
, CTX
CTX
CTX is a three-letter abbreviation with multiple meanings:* Caltex, where CTX is the stock symbol for Caltex Australia Limited* Cefotaxime, an antibiotic* Centrex, a telephone service* Cerebrotendineous xanthomatosis, a genetic disorder...
, and HiRISE
HiRISE
High Resolution Imaging Science Experiment is a camera on board the Mars Reconnaissance Orbiter. The 65 kg , $40 million instrument was built under the direction of the University of Arizona's Lunar and Planetary Laboratory by Ball Aerospace & Technologies Corp....
. Detailed altimetry was collected by MOLA
Mars Orbiter Laser Altimeter
right|thumb|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 was one of five instruments on board the Mars Global Surveyor spacecraft, which operated in Mars orbit from September 1997 to...
.
The Mars Reconnaissance Orbiter
Mars Reconnaissance Orbiter
Mars Reconnaissance Orbiter is a NASA multipurpose spacecraft designed to conduct reconnaissance and Exploration of Mars from orbit...
's Shallow Radar gave a strong reflection from the top and base of LDAs, meaning that pure water ice made up the bulk of the formation (between the two reflections), strong evidence that the LDAs in Hellas Planitia
Hellas 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...
are glaciers covered with a thin layer of rocks. Since lineated valley terrain is derived from lobate debris aprons, it probably contains buried ice—at least in places.
Connection to past climate
Studies of LDAs and LVF give evidence that there have been multiple episodes of glaciation on Mars, including ones that produced glaciers nearing a kilometre in thickness. These ice ages are related to major climate shifts caused by major variations in axial tiltAxial tilt
In astronomy, axial tilt is the angle between an object's rotational axis, and a line perpendicular to its orbital plane...
. Earth's rather large moon prevents large changes in its tilt. The two moons of Mars are tiny. So Mars undergoes large periods when its ice cap receives more direct sunlight.
During this time ice in the cap sublimates, and thick snow falls in mid-latitudes — the zones where concentric crater fill, lineated valley fill and lobate debris aprons are common. The distribution of craters on LVF indicates a late Amazonian age for at least some areas.
Where located
Lineated valley fill is common in the middle latitudes, especially near the northern dichotomyMartian dichotomy
The most conspicuous feature of Martian surface geology is a sharp contrast, known as the Martian dichotomy, between the rugged southern highlands and the relatively smooth northern basins. The two hemispheres differ in elevation by 1 to 3 km...
boundary. The Nilosyrtis Mensae
Nilosyrtis Mensae
Nilosyrtis Mensae is an area of Mars in the Casius quadrangle. It is centered on the coodinates of 36.87° N and 67.9° E. Its western and eastern longitudes are 51.1° E and 74.4° E. North and south latitudes are 36.87° N and 29.61° N. Nilosyrtis Mensae is just to the east of Protonilus Mensae...
, Protonilus Mensae
Protonilus Mensae
Protonilus Mensae is an area of Mars in the Ismenius Lacus quadrangle. It is centered on the coordinates of 43.86° N and 49.4° E. Its western and eastern longitudes are 37° E and 59.7° E. North and south latitudes are 47.06° N and 39.87° N. Protonilus Mensae is between Deuteronilus Mensae and...
and Deuteronilus Mensae
Deuteronilus Mensae
Deuteronilus Mensae is a region on Mars 937 km across and centered at . It covers 344° -325° West and 40°-48° North. Deuteronilus region lies just to the north of Arabia Terra and is included in the Ismenius Lacus quadrangle. It is along the dichotomy boundary, that is between the old,...
bear many examples of LVF. Ismenius Lacus quadrangle and Hellas quadrangle contain many valleys displaying lineated valley fill.
LVF and other ice-related forms are collectively known as fretted terrain
Fretted terrain
Fretted terrain is a type of surface feature common to certain areas of Mars and discovered in Mariner 9 images. It lies between two different types of terrain...
, which includes winding and straight valleys with isolating plateaus and mesas.
Importance of lineated valley fill
Studies of lineated valley fill have added evidence that the climate of MarsClimate of Mars
The climate of Mars has been an issue of scientific curiosity for centuries, not least because Mars is the only terrestrial planet whose surface can be directly observed in detail from the Earth....
has undergone many large changes in the past.
At times there is snow, and at times the snow may melt. The resulting small areas of liquid water cause weathering of the rocks and may provide a favourable environment for life. Understanding lineated valley fill and other manifestations of buried ice will allow future colonists to find sources of water
Water on Mars
Water on Mars is a psychedelic rock and electronic music group from Quebec City, Québec, Canada. The music trio is led by Philippe Navarro, guitarist, vocalist, arranger, producer, principal lyricist, and music composer....
.
Reull Vallis
Reull Vallis
Reull Vallis is a valley on Mars that appears to have been carved by water. It runs westward into the Channels of Reull Vallis which runs north westwards into Hellas Planitia. It is named after the Gaelic word for planet.- Lineated Floor Deposits :...
, as pictured below, displays such deposits. Sometimes the lineated floor deposits show a chevron pattern which is further evidence of movement. The picture below taken with HiRISE of Reull Vallis shows these patterns.
See also
- Geology of MarsGeology of MarsThe geology of Mars is the scientific study of the surface, crust, and interior of the planet Mars. It emphasizes the composition, structure, history, and physical processes that shape the planet. It is fully analogous to the field of terrestrial geology. In planetary science, the term geology is...
- Lobate debris apronLobate Debris ApronLobate debris aprons are geological features on Mars, first seen by the Viking Orbiters, consisting of piles of rock debris below cliffs. These features have a convex topography and a gentle slope from cliffs or escarpments, which suggest flow away from the steep source cliff...
- Concentric crater fillConcentric crater fillConcentric crater fill is when the floor of a crater is mostly covered with a large number of parallel ridges. It is common in the mid-latitudes of Mars, and is widely believed to be caused by glacial movement...
- GlacierGlacierA glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
- Glaciers on MarsGlaciers on MarsGlaciers formed much of the observable surface in large areas of Mars. Most of the area in high latitudes, especially the Ismenius Lacus quadrangle, is believed to still contain enormous amounts of water ice. Recent evidence has led many planetary scientists to believe that water ice still exists...
- Protonilus MensaeProtonilus MensaeProtonilus Mensae is an area of Mars in the Ismenius Lacus quadrangle. It is centered on the coordinates of 43.86° N and 49.4° E. Its western and eastern longitudes are 37° E and 59.7° E. North and south latitudes are 47.06° N and 39.87° N. Protonilus Mensae is between Deuteronilus Mensae and...
- Deuteronilus MensaeDeuteronilus MensaeDeuteronilus Mensae is a region on Mars 937 km across and centered at . It covers 344° -325° West and 40°-48° North. Deuteronilus region lies just to the north of Arabia Terra and is included in the Ismenius Lacus quadrangle. It is along the dichotomy boundary, that is between the old,...
- Nilosyrtis MensaeNilosyrtis MensaeNilosyrtis Mensae is an area of Mars in the Casius quadrangle. It is centered on the coodinates of 36.87° N and 67.9° E. Its western and eastern longitudes are 51.1° E and 74.4° E. North and south latitudes are 36.87° N and 29.61° N. Nilosyrtis Mensae is just to the east of Protonilus Mensae...