Peace Vallis is an ancient stream valley on the northern rim of

Gale Crater Gale is a crater, and probable dry lake, at in the northwestern part of the Aeolis quadrangle on Mars. It is in diameter and estimated to be about 3.5–3.8 billion years old. The crater was named after Walter Frederick Gale, an amateur ast ...

on the planet

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

. It is notable for its associated

alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but a ...

which lies near the Mars Science Laboratory ''Curiosity'' landing site (

Bradbury Landing Bradbury Landing is the August 6, 2012, landing site within Gale crater on planet Mars of the Mars Science Laboratory (MSL) ''Curiosity'' rover. On August 22, 2012, on what would have been his 92nd birthday, NASA named the site for author Ra ...

). The valley and alluvial fan provide evidence for geologically recent ( Amazonian-aged) fluvial activityNewsom, H.E.; Scuderi, L.A.; Gallegos, Z.E.; Williams, J.M.; Dimitracopoulos, F.D.; Tornabene, L.L.; Wiens, R.C.; Gasnault, O. (2021). Evidence for Glacial and Fluvial Processes on Gale Crater Rim—Dulce Vallis. ''52nd Lunar and Planetary Science Conference,'' Abstract #2256. https://www.hou.usra.edu/meetings/lpsc2021/pdf/2256.pdf.Ehlmann, B.L.; Buz, J. (2015). Mineralogy and fluvial History of the Watersheds of Gale, Knobel, and Sharp Craters: A Regional Context for the Mars Science Laboratory Curiosity's Exploration. ''Geophys. Res. Lett.,'' 42, 264–273, doi:10.1002/2014GL062553. https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/2014GL062553. and sustained water flowWilliams, R.M.E.; Grotzinger, J.P.; Dietrich, W.E.; Gupta, S.; Sumner, D.Y. et al. (2013). Martian Fluvial Conglomerates at Gale Crater. ''Science,'' 340, 1068, doi: 10.1126/science.1237317. on Mars. Recent high-resolution orbital images of Peace Vallis and its watershed also suggest that at least one glacial episode affected Gale crater. Newsom, H.E.; Scuderi, L.A.; Gallegos, Z.E.; Tornabene, L.L.; Wiens, R.C. (2020). Evidence for Glacial Processes on Gale Crater Rim Surfaces from New HiRise Observations. ''51st Lunar and Planetary Science Conference,'' Abstract #2609. https://www.hou.usra.edu/meetings/lpsc2020/pdf/2609.pdf. All of this evidence has implications for the history of

water on Mars Almost all water on Mars today exists as ice, though it also exists in small quantities as vapor in the atmosphere. What was thought to be low-volume liquid brines in shallow Martian soil, also called recurrent slope lineae, may be grains of ...

and the planet's long-term

habitability Habitability refers to the adequacy of an environment for human living. Where housing is concerned, there are generally local ordinances which define habitability. If a residence complies with those laws it is said to be habitable. In extreme e ...

.Scuderi, L.A.; Gallegos, Z.E.; Newsom, H.E.; Wiens, R..C. (2019). Amazonian Groundwater Springline at Peace Vallis Fan, Gale Crater; Implications for a Late Period of Surface Habitability. ''Mars Extant Life: What's Next? Conference,'' Abstract #5043. https://www.hou.usra.edu/meetings/lifeonmars2019/pdf/5043.pdf. Understanding Peace Vallis and its fan also provides geologic context for the rocks observed on the ground by the ''Curiosity'' rover.Palucis, M.C.; Dietrich, W.E.; Hayes, A.; Williams, R.M.E. et al. (2013). Origin and Evolution of the Peace Vallis Fan System that Drains into the Curiosity Landing Area, Gale Crater. "44th Lunar and Planetary Science Conference", Abstract #1607. https://www.lpi.usra.edu/meetings/lpsc2013/pdf/1607.pdf.

Location and Regional Context

The valley is centered at in the northeastern

Aeolis quadrangle The Aeolis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Aeolis quadrangle is also referred to as MC-23 (Mars Chart-23). The Aeolis quadrangle c ...

of Mars and drains approximately of the northern rim of Gale Crater.Newsom, H.E.; Scuderi, L.A.; Gallegos, Z.E.; Nagle-McNaughton, T.P.; Tornabene, L.L. et al. (2019). Southern Watershed and Fluvial History of the Peace Vallis Fan System, Gale Crater, Mars. ''9th International Conference on Mars,'' Abstract #6119. https://www.hou.usra.edu/meetings/ninthmars2019/pdf/6119.pdf. While the stream was active, surface water and groundwater drained to the south into a low-lying plain in the northern interior of the crater ( Aeolis Palus) where the stream valley

debouche In hydrology, a debouch (or debouche) is a place where runoff from a small, confined space discharges into a larger, broader body of water. The word is derived from the French verb ''déboucher'' (), which means "to unblock, to clear". The term ...

d into a large alluvial fan (Peace Vallis fan). Gale crater itself is a -diameter impact crater that straddles the martian hemispheric dichotomy between the heavily cratered southern highlands and the lower elevation plains ( Elysium Planitia) to the north. Gale crater is noteworthy for its enigmatic -high crescent-shaped central mound,

Aeolis Mons Mount Sharp, officially Aeolis Mons (), is a mountain on Mars. It forms the central peak within Gale (crater), Gale crater and is located around , rising high from the valley floor. Its ID in the United States Geological Survey's Gazetteer of ...

(known informally as Mt. Sharp). The crater is late

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 possible presence of abundant surface water. The absolute age of the Noachian period is uncertain ...

or Early

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 transitio ...

in age (approximately 3.65 to 3.55 billion years old).Le Deit, L.; Hauber, E.; Fueten, F.; Pondrelli, M.; Pio Rossi, A.; Jaumann, R. (2013). Sequence of Infilling Events in Gale Crater, Mars: Results from Morphology, Stratigraphy, and Mineralogy. ''J. Geophys. Res.,'' 118, 2439–2473, doi:10.1002/2012JE004322, 2013. The northern rim of Gale Crater is heavily eroded and hosts a number of geomorphic features indicating the effects of flowing water. These include valleys, gullies, and canyons; sinuous ridges interpreted to be inverted channels; and alluvial fan-like mesas.Anderson, R.B.; Bell, J.F. (2010). Geologic Mapping and Characterization of Gale Crater and Implications for Its Potential as a Mars Science Laboratory Landing Site. ''Mars,'' 5, 76–128. Peace Vallis and its alluvial fan is the largest and best studied of these fluvial features in northern Gale Crater.

Name

Peace Vallis is named after the Peace River in Alberta and British Columbia, Canada. The name was adopted by the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

(IAU) on September 26, 2012. '' Vallis'' is the Latin word for valley.

Valley and Drainage Basin

Peace Vallis is a valley network characterized by a branching (dendritic) pattern of tributary valleys that resembles river drainage basins on Earth. They are common on the older heavily cratered regions of Mars. Most planetary scientists agree that valley networks were formed by flowing water, but the source of the water is still debated.Carr, M.H. ''The Surface of Mars''; Cambridge University Press: New York, 2006 Some argue that rainfall on a warm and wet early mars produced them.Craddock, R.A.; Howard, A.D. (2002). The Case for Rainfall on a Warm, Wet Early Mars. ''J. Geophys. Res.,'' 107(E11), 5111, doi:10.1029/2001JE001505. https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2001JE001505. Others have suggested they were produced by

mass wasting Mass wasting, also known as mass movement, is a general term for the movement of rock or soil down slopes under the force of gravity. It differs from other processes of erosion in that the debris transported by mass wasting is not entrained in ...

,Carr, M.H. (1995). The Martian Drainage System and the Origin of Valley Networks and Fretted Channels. ''J. Geophys. Res.,'' 100(E4), 7479–7507. spring sapping, Squyres, S.W. (1989). Early Mars: Wet and Warm, or Just Wet? 20th Lunar and Planetary Science Conference Abstract #1044. or from

snowmelt In hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many par ...

Carr, M.H. and Head, J.W. (2003). Basal Melting of Snow on Early Mars: A Possible Origin of Some Valley Networks. ''Geophys. Res. Lett.,'' 30(24), 2245, doi:10.1029/2003GL018575. on an ancient Mars whose climate was dry and cold much like today's. The Peace Vallis

drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...

(or catchment) covers an area of about 1,500 km² (579 mi²). This area sits 1,300 m (4,265 ft) above the crater floor and consists of gently sloping plains interspersed with hills roughly 100 to 350 m (328 to 1,148 ft) high. These irregular hills are mostly mantled with debris that appear to be some combination of aeolian deposits and

colluvium Colluvium (also colluvial material or colluvial soil) is a general name for loose, unconsolidated sediments that have been deposited at the base of hillslopes by either rainwash, sheetwash, slow continuous downslope creep, or a variable combinati ...

. Palucis, M.; Dietrich, W.; Hayes, A.; Williams, R. et al. (2014). The Origin and Evolution of the Peace Vallis Fan System That Drains to the ''Curiosity'' landing area, Gale Crater, Mars. ''J. Geophys. Res.,'' 119, 705–728. Bibcode:2014JGRE..119..705P. doi:10.1002/2013je004583. https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2013JE004583. Erosion of the watershed surface has produced a mottled scoured appearance, suggesting mobilization and transport of sediments into topographic lows. Compared with most terrestrial valleys carved by rainfall, the

drainage density Drainage density is a quantity used to describe physical parameters of a drainage basin. First described by Robert E. Horton, drainage density is defined as the total length of channel in a drainage basin divided by the total area, represented by ...

(stream length per unit area) of Peace Vallis and its tributaries is very low. There is a lack of highly integrated fluvial channels, Newsom, H.E.; Scuderi, L.A.; Gallegos, Z.E. et al. (2020). New HiRISE Observations of Gale Crater Rim Surfaces—Evidence for Glacial Processes. ''American Geophysical Union, Fall Meeting,'' No. P038-01. and the areas between the tributary valleys (interfluves) are undissected by smaller valleys or gullies. The drainage density of the Peace Vallis system has been estimated to be 0.15 km^–1. In contrast, drainage densities of rivers on Earth range from 2 to 30 km^–1. Carr, M.C. ''Water on Mars.'' Oxford University Press: New York, 2006, 229 pp. Factors that control drainage density include slope, rock type (which determines

infiltration capacity Infiltration is the process by which water on the ground surface enters the soil. It is commonly used in both hydrology and soil sciences. The infiltration capacity is defined as the maximum rate of infiltration. It is most often measured in meter ...

) Melosh, H.J. ''Planetary Surface Processes.'' Cambridge University Press: Cambridge U.K., 2011, 500 pp. and climate (mainly precipitation). The low drainage density of Peace Vallis suggests an environment of relatively gentle slopes, very low (or infrequent) precipitation, permeable soils or bedrock, or some combination of the three. Huggett, R.J. ''Fundamentals of Geomorphology.'' Routledge: New York, 2007, 483 pp. The valleys are U-shaped in

topographic profile A topographic profile or topographic cut is a representation of the relief of the terrain that is obtained by cutting transversely the lines of a topographic map. Each contour line can be defined as a closed line joining relief points at equal hei ...

, with widths ranging from 80 to 900 meters (262 to 2,950 feet) and a mean of 300 meters (984 feet). The main or trunk valley is about 32 km (20 miles) long. ''Curiosity'' rover landed near the end of the Peace Vallis fan. Peace Vallis fan covers and obtained water from an area of . Peace Vallis enters Gale Crater through a gap in its rim. Calculations suggest that the fan has an average thickness of . Numerous inverted channels are visible on the western surface of the fan. Runoff through Peace Vallis that made the fan is estimated to be between ; therefore a hydrologic cycle probably lasted at least thousands of years. The water that flowed in Peace Vallis is believed to be from precipitation, possibly in the form of snow.

Images

Image:MSL landing sites topograph.png, Map of actual (and proposed) Rover landing sites including

. Image:Mars Science Laboratory landing ellipse reduced.jpg,

- Landing site is within Aeolis Palus near Aeolis Mons (Mount Sharp) - North is down. Image:Curiosity landing site (artist's rendition with 2x vertical exaggeration).jpg,

- Landing site is noted - also,

(blue) and sediment layers in

(cutaway). Image:PIA16064-Mars Curiosity Rover Treasure Map.jpg, ''Curiosity'' rover landing site (green dot) - Blue dot marks Glenelg Intrigue - Blue spot marks the base of

Mount Sharp Mount Sharp, officially Aeolis Mons (), is a mountain on Mars. It forms the central peak within Gale crater and is located around , rising high from the valley floor. Its ID in the United States Geological Survey's Gazetteer of Planetary Nomen ...

- a planned area of study. Image:Curiosity Rover (Exaggerated Color) - HiRISE - 20120814.jpg, ''Curiosity'' rover landing site (

) viewed by

HiRISE High Resolution Imaging Science Experiment is a camera on board the '' Mars Reconnaissance Orbiter'' which has been orbiting and studying Mars since 2006. The 65 kg (143 lb), US$40 million instrument was built under the direction ...

( MRO) (August 14, 2012). Image:673885main PIA15986-full full.jpg, Aeolis Palus and

as viewed by the ''Curiosity'' rover (August 6, 2012). Image:PIA16105 malin04ano-br2.jpg, Layers at the base of

- dark rock in inset is same size as the ''Curiosity'' rover ( white balanced image). Image:PIA16068 - Mars Curiosity Rover - Aeolis Mons - 20120817.jpg,

as viewed from the ''Curiosity'' rover (August 9, 2012) ( white balanced image). Image:676029main_pia16052-color-full_full.jpg,

rim about North of the ''Curiosity'' rover (August 9, 2012). Image:PIA17085-MarsCuriosityRover-TraverseMap-Sol351-20130801.jpg, First-Year and First-Mil
Traverse Map
of the ''Curiosity'' rover on Mars (August 1, 2013)
3-D
.

References

External links