Lineated valley fill

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Lineated valley fill (LVF), 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. [1] [2] Hundreds of metres of ice probably lie protected in LVF under a thin layer of debris. [3] [4] [5] 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 glaciers on Earth show similar ridges. High-resolution pictures taken with HiRISE reveal that some of the surfaces of lineated valley fill are covered with strange patterns called closed-cell and open-cell brain terrain. The terrain resembles a human brain. It is believed to be caused by cracks in the surface accumulating dust and other debris, together with ice sublimating from some of the surfaces. The cracks are the result stress from gravity and seasonal heating and cooling. [6] [7] This same type of surface is present on Lobate debris aprons and Concentric crater fill so all three are believed to be related.

Contents

Lineated floor deposits began as lobate debris aprons (LDAs), which form as material leaves narrow mountain valleys and spreads out as an apron. [8] 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. [5] [9] [10] [11]

In the regions where LVF and LDAs occur, many craters have concentric crater fill: large ridges and other surfaces nicknamed brain terrain, after the surface corrugations of the human brain. [12]

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. [8] [13] [14]

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 tilt. [15] [16] 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. [17] [18] 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. [19] The distribution of craters on LVF indicates a late Amazonian age for at least some areas. [1] [20]

Where located

Lineated valley fill is common in the middle latitudes, especially near the northern dichotomy 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. [21]

Importance of lineated valley fill

Studies of lineated valley fill have added evidence that the climate of Mars has undergone many large changes in the past. [22]

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.

See also

Related Research Articles

Terra Sabaea

Terra Sabaea is a large area on Mars. Its coordinates are 2°N42°E and it covers 4,700 kilometres (2,900 mi) at its broadest extent. It was named in 1979 after a classic albedo feature on the planet. Terra Sabaea is fairly large and parts of it are found in five quadrangles: Arabia quadrangle, Syrtis Major quadrangle, Iapygia quadrangle, Ismenius Lacus quadrangle, and Sinus Sabaeus quadrangle.

Deuteronilus Mensae

Deuteronilus Mensae is a region on Mars 937 km across and centered at 43.9°N 337.4°W. 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, heavily cratered southern highlands and the low plains of the northern hemisphere. The region contains flat-topped knobby terrain that may have been formed by glaciers at some time in the past. Deuteronilus Mensae is to the immediate west of Protonilus Mensae and Ismeniae Fossae. Glaciers persist in the region in modern times, with at least one glacier estimated to have formed as recently as 100,000 to 10,000 years ago. Recent evidence from the radar on the Mars Reconnaissance Orbiter has shown that parts of Deuteronilus Mensae do indeed contain ice.

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 and covers 0° to 60° east longitude and 30° to 65° north latitude. The quadrangle uses a Lambert conformal conic projection at a nominal scale of 1:5,000,000 (1:5M). The Ismenius Lacus quadrangle is also referred to as MC-5. The southern and northern borders of the Ismenius Lacus quadrangle are approximately 3,065 km (1,905 mi) and 1,500 km (930 mi) wide, respectively. The north-to-south distance is about 2,050 km (1,270 mi). The quadrangle covers an approximate area of 4.9 million square km, or a little over 3% of Mars’ surface area. The Ismenius Lacus quadrangle contains parts of Acidalia Planitia, Arabia Terra, Vastitas Borealis, and Terra Sabaea.

The Casius 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 north-central portion of Mars’ eastern hemisphere and covers 60° to 120° east longitude and 30° to 65° north latitude. The quadrangle uses a Lambert conformal conic projection at a nominal scale of 1:5,000,000 (1:5M). The Casius quadrangle is also referred to as MC-6. Casius quadrangle contains part of Utopia Planitia and a small part of Terra Sabaea. The southern and northern borders of the Casius quadrangle are approximately 3,065 km and 1,500 km wide, respectively. The north to south distance is about 2,050 km. The quadrangle covers an approximate area of 4.9 million square km, or a little over 3% of Mars’ surface area.

The Cebrenia 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’ eastern hemisphere and covers 120° to 180° east longitude and 30° to 65° north latitude. The quadrangle uses a Lambert conformal conic projection at a nominal scale of 1:5,000,000 (1:5M). The Cebrenia quadrangle is also referred to as MC-7. It includes part of Utopia Planitia and Arcadia Planitia. The southern and northern borders of the Cebrenia quadrangle are approximately 3,065 km (1,905 mi) and 1,500 km (930 mi) wide, respectively. The north to south distance is about 2,050 km (1,270 mi). The quadrangle covers an approximate area of 4.9 million square km, or a little over 3% of Mars’ surface area.

Moreux (crater)

Moreux is a crater in the Ismenius Lacus quadrangle on Mars with a diameter of 138 kilometers. It is located at 42.1° north latitude and 315.6° west longitude and was named by IAU's Working Group for Planetary System Nomenclature after Theophile Moreux, a French astronomer and meteorologist (1867–1954).

The Phlegra Montes are a system of eroded Hesperian–Noachian-aged massifs and knobby terrain in the mid-latitudes of the northern lowlands of Mars, extending northwards from the Elysium Rise towards Vastitas Borealis for nearly 1,400 km (870 mi). The mountain ranges separate the large plains provinces of Utopia Planitia (west) and Amazonis Planitia (east), and were named in the 1970s after a classical albedo feature. The massif terrains are flanked by numerous parallel wrinkle ridges known as the Phlegra Dorsa.

Lobate debris apron

Lobate debris aprons (LDAs) 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. In addition, lobate debris aprons can show surface lineations as do rock glaciers on the Earth.

Fretted terrain is a type of surface feature common to certain areas of Mars and was discovered in Mariner 9 images. It lies between two different types of terrain. The surface of Mars can be divided into two parts: low, young, uncratered plains that cover most of the northern hemisphere, and high-standing, old, heavily cratered areas that cover the southern and a small part of the northern hemisphere. Between these two zones is a region called the Martian dichotomy and parts of it contain fretted terrain. This terrain contains a complicated mix of cliffs, mesas, buttes, and straight-walled and sinuous canyons. It contains smooth, flat lowlands along with steep cliffs. The scarps or cliffs are usually 1 to 2 km high. Channels in the area have wide, flat floors and steep walls. Fretted terrain shows up in northern Arabia, between latitudes 30°N and 50°N and longitudes 270°W and 360°W, and in Aeolis Mensae, between 10 N and 10 S latitude and 240 W and 210 W longitude. Two good examples of fretted terrain are Deuteronilus Mensae and Protonilus Mensae.

Lipik (crater)

Lipik Crater is a crater in the Hellas quadrangle of Mars, located at 38.42° S and 248.43° W. It is 56 km in diameter and was named after Lipik, a town in Croatia. Close-up pictures of the crater show glacial features. The crater is not very deep, so much ice and dust may have accumulated over the years. If one measures the diameter of a crater, the original depth can be estimated with various ratios. Because of this relationship, researchers have found that many Martian craters contain a great deal of material; much of it is believed to be ice deposited when the climate was different.

A concentric crater fill (CCF) is a landform where the floor of a crater is mostly covered with many parallel ridges. It is common in the mid-latitudes of Mars, and is widely believed to be caused by glacial movement. Areas on Mars called Deuteronilus Mensae and Protonilus Mensae contain many examples of concentric crater fill.

Ring mold crater Type of crater on Mars

A Ring mold crater is a kind of crater on the planet Mars that looks like the ring molds used in baking. They are believed to be caused by an impact into ice. The ice is covered by a layer of debris. They are found in parts of Mars that have buried ice. Laboratory experiments confirm that impacts into ice result in a "ring mold shape." They are also bigger than other craters in which an asteroid impacted solid rock. Impacts into ice warm the ice and cause it to flow into the ring mold shape. These craters are common in lobate debris aprons and lineated valley fill. Many have been found in Mamers Valles, a channel found along the dichotomy boundary in Deuteronilus Mensae. They may be an easy way for future colonists of Mars to find water ice.

Protonilus Mensae Martian plain

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 Nilosyrtis Mensae; all lie along the Martian dichotomy boundary. Its name was adapted by the IAU in 1973.

Nilosyrtis Mensae Fretted terrain in the Casius quadrangle on Mars

Nilosyrtis Mensae is an area of Mars in the Casius quadrangle. It is centered on the coordinates 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 and both lie along the Martian dichotomy boundary. Its name was adapted by the IAU in 1973. It was named after a classical albedo feature, and it is 705 km (438 mi) across.

Glaciers on Mars

Glaciers, loosely defined as patches of currently or recently flowing ice, are thought to be present across large but restricted areas of the modern Martian surface, and are inferred to have been more widely distributed at times in the past. Lobate convex features on the surface known as viscous flow features and lobate debris aprons, which show the characteristics of non-Newtonian flow, are now almost unanimously regarded as true glaciers.

Evidence of water on Mars found by Mars Reconnaissance Orbiter

The Mars Reconnaissance Orbiter's HiRISE instrument has taken many images that strongly suggest that Mars has had a rich history of water-related processes. Many features of Mars appear to be created by large amounts of water. That Mars once possessed large amounts of water was confirmed by isotope studies in a study published in March 2015, by a team of scientists showing that the ice caps were highly enriched with deuterium, heavy hydrogen, by seven times as much as the Earth. This means that Mars has lost a volume of water 6.5 times what is stored in today's polar caps. The water for a time would have formed an ocean in the low-lying Mare Boreum. The amount of water could have covered the planet about 140 meters, but was probably in an ocean that in places would be almost 1 mile deep.

The common surface features of Mars include dark slope streaks, dust devil tracks, sand dunes, Medusae Fossae Formation, fretted terrain, layers, gullies, glaciers, scalloped topography, chaos terrain, possible ancient rivers, pedestal craters, brain terrain, and ring mold craters.

Brain terrain Feature of the Martian surface

Brain terrain, also called knobs-brain coral and brain coral terrain, is a feature of the Martian surface, consisting of complex ridges found on lobate debris aprons, lineated valley fill and concentric crater fill. It is so named because it suggests the ridges on the surface of the human brain. Wide ridges are called closed-cell brain terrain, and the less common narrow ridges are called open-cell brain terrain. It is thought that the wide closed-cell terrain contains a core of ice, and when the ice disappears the center of the wide ridge collapses to produce the narrow ridges of the open-cell brain terrain. Shadow measurements from HiRISE indicate the ridges are 4-5 meters high. Brain terrain has been observed to form from what has been called an "Upper Plains Unit." The process begins with the formation of stress cracks. The upper plains unit fell from the sky as snow and as ice coated dust.

Sinton is a crater in the Ismenius Lacus quadrangle on Mars, located at 40.72°N and 328.35°W. Sinton Crater lies in the northern hemisphere south of the very large crater Lyot. It is 65.25 km in diameter and was named after Harvard astronomer William M. Sinton. The name was approved in 2007.

Upper plains unit

The upper plains unit is the remnants of a 50-100 meter thick mantling that has been discovered in the mid-latitudes of the planet Mars. It was first investigated in the Deuteronilus Mensae region, but it occurs in other places as well. The remnants consist of sets of dipping layers in impact craters, in depressions, and along mesas. Sets of dipping layers may be of various sizes and shapes—some look like Aztec pyramids from Central America.

References

  1. 1 2 Head, J.; Marchant, D.R.; Agnew, M.C.; Fassett, C.I.; Kreslavsky, M.A. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for late Amazonian obliquity-driven climate change". Earth Planet. Sci. Lett. 241 (3–4): 663–671. Bibcode:2006E&PSL.241..663H. doi:10.1016/j.epsl.2005.11.016.
  2. ↑ Head, J., et al. 2006. Modification if the dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation. Geophys. Res. Lett. 33
  3. ↑ Morgan, G.; Head, James W.; Marchant, David R. (2009). "Lineated valley fill (LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: constraints on the extent, age, and episodicity of Amazonian glacial events". Icarus. 202 (1): 22–38. Bibcode:2009Icar..202...22M. doi:10.1016/j.icarus.2009.02.017.
  4. ↑ Head, J. and D. Marchant. 2006. Evidence for global-scale northern mid-latitude glaciation in the Amazonian period of Mars: Debris-covered glacial and valley glacial deposits in the 30 - 50 N latitude band. Lunar. Planet. Sci. 37. Abstract 1127
  5. 1 2 Head, J. & D. Marchant (2006). "Modification of the walls of a Noachian crater in northern Arabia Terra (24E, 39N) during mid-latitude Amazonian glacial epochs on Mars: Nature and evolution of lobate debris aprons and their relationships to lineated valley fill and glacial systems". Lunar Planet. Sci. 37: Abstract # 1126.
  6. ↑ Mellon, M. 1997. Small-scale polygonal features on Mars: Seasonal thermal contraction cracks in permafrost. J. Geophysical Res: 102. 25,617-625,628.
  7. ↑ Ley, J. et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial processes. Icarus: 202. 462-476.
  8. 1 2 Souness C., Hubbard B. (2013). "An alternative interpretation of late Amazonian ice flow: Protonilus Mensae, Mars". Icarus. 225 (1): 495–505. Bibcode:2013Icar..225..495S. doi:10.1016/j.icarus.2013.03.030.
  9. ↑ Kress, A., J. Head (2008). "Ring-mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice". Geophys. Res. Lett. 35 (23): L23206–8. Bibcode:2008GeoRL..3523206K. doi: 10.1029/2008gl035501 .CS1 maint: multiple names: authors list (link)
  10. ↑ Baker, D.; Head, James W.; Marchant, David R. (2010). "Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian". Icarus. 207 (1): 186–209. Bibcode:2010Icar..207..186B. doi:10.1016/j.icarus.2009.11.017.
  11. ↑ Kress., A. & J. Head (2009). "Ring-mould craters on lineated valley fill, lobate debris aprons, and concentric crater fill on Mars: Implications for near-surface structure, composition, and age". Lunar Planet. Sci. 40: abstract 1379.
  12. ↑ Levy, J.; Head, James W.; Marchant, David R. (2009). "Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial processes". Icarus. 202 (2): 462–476. Bibcode:2009Icar..202..462L. doi:10.1016/j.icarus.2009.02.018.
  13. ↑ Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf
  14. ↑ Head, JW; Neukum, G; Jaumann, R; Hiesinger, H; Hauber, E; Carr, M; Masson, P; Foing, B; et al. (2005). "Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars". Nature. 434 (7031): 346–350. Bibcode:2005Natur.434..346H. doi:10.1038/nature03359. PMID   15772652. S2CID   4363630.
  15. ↑ Madeleine, J. et al. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096.
  16. ↑ Barlow, N. 2008. Mars: An Introduction to its Interior, Surface and Atmosphere. Cambridge University Press. ISBN   978-0-521-85226-5
  17. ↑ "HiRISE | Dissected Mantled Terrain (PSP_002917_2175)".
  18. ↑ Forget, F., et al. 2006. Planet Mars Story of Another World. Praxis Publishing, Chichester, UK. ISBN   978-0-387-48925-4
  19. ↑ Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN   978-0-521-87201-0
  20. ↑ Levy, J.; et al. (2007). "Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary". J. Geophys. Res. 112 (E8): E08004. Bibcode:2007JGRE..112.8004L. doi: 10.1029/2006je002852 .
  21. ↑ Sharp, R (1973). "Mars Fretted and chaotic terrains" (PDF). J. Geophys. Res. 78 (20): 4073–4083. Bibcode:1973JGR....78.4073S. doi:10.1029/JB078i020p04073.
  22. ↑ Kreslavsky, M. & J. Head (2006). "Modification of impact craters in the northern planes of Mars: Implications for the Amazonian climate history". Meteorit. Planet. Sci. 41 (10): 1633–1646. Bibcode:2006M&PS...41.1633K. CiteSeerX   10.1.1.715.3727 . doi: 10.1111/j.1945-5100.2006.tb00441.x .
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