Mars surface color

Short description: Extraterrestrial geography

Yogi Rock, analyzed by the Sojourner rover (July 4, 1997)

File:Mars 360 animation.webm

Mars surface map rendered using a color map and a heightmap from NASA

The surface color of the planet Mars appears reddish from a distance because of rusty atmospheric dust.[1] From close up, it looks more of a butterscotch,[1] and other common surface colors include golden, brown, tan, and greenish, depending on minerals.[1]

The apparent colour of the Martian surface enabled humans to distinguish it from other planets early in human history and motivated them to weave fables of war in association with Mars. One of its earliest recorded names, Har decher, literally meant "Red One" in Egyptian.[2] Its color may have also contributed to a malignant association in Indian astrology, as it was given the names Angaraka and Lohitanga, both reflecting the distinctively red color of Mars as seen by the naked eye.[2]

## Contents

* 1 Reason for red and its extensiveness
* 2 The occurrence of nanophase ferric oxides (npOx) in dust
* 3 Red skies on Mars
* 4 References
* 5 External links

## Reason for red and its extensiveness

Modern observations indicate that Mars's redness is skin deep. The Martian surface looks reddish primarily because of a ubiquitous dust layer (particles are typically between 3 μm to 45 μm across[3][4]) that is typically on the order of millimeters thick. Even where the thickest deposits of this reddish dust occur, such as the Tharsis area, the dust layer is probably not more than 2 meters (6.6 ft) thick.[5] Therefore, the reddish dust is essentially an extremely thin veneer on the Martian surface and does not represent the bulk of the Martian subsurface in any way.

Curiosity's view of Martian soil and boulders after crossing the "Dingo Gap" sand dune (February 9, 2014; raw color)

Martian dust is reddish mostly due to the spectral properties of nanophase ferric oxides (npOx) that tend to dominate in the visible spectrum. The specific npOx minerals have not been fully constrained, but nanocrystalline red hematite (α-Fe2O3) may be the volumetrically dominant one,[6] at least at the less than 100 μm sampling depth[7] of infrared remote sensors such as the Mars Express OMEGA instrument. The rest of the iron in the dust, perhaps as much as 50% of the mass, may be in titanium enriched magnetite (Fe3O4).[8] Magnetite is usually black in colour with a black streak,[9] and does not contribute to the reddish hue of dust.

The mass fraction of chlorine and sulfur in the dust is greater than that which has been found (by the Mars Exploration Rovers Spirit and Opportunity) in the soil types at Gusev crater and Meridiani Planum. The sulfur in the dust also shows a positive correlation with npOx.[10] This suggests that very limited chemical alteration by thin brine films (facilitated by the formation of frost from atmospheric H2O) may be producing some of the npOx.[10] In addition, remote sensing observations of atmospheric dust (which shows slight compositional and grain size differences from surface dust), indicates that the bulk volume of dust grains consists of plagioclase feldspar and zeolite, along with minor pyroxene and olivine components.[11] Such fine material can be generated easily via mechanical erosion from feldspar-rich basalts, such as rocks in the southern highlands on Mars.[11] Collectively, these observations indicate that any chemical alteration of dust by aqueous activity has been very minor.

## The occurrence of nanophase ferric oxides (npOx) in dust

There are several processes that can yield npOx as an oxidation product without the involvement of free oxygen (O2). One or more of those processes may have dominated on Mars, since atmospheric modeling over geologic time scales indicates that free O2 (generated mostly via the photodissociation of water (H2O))[12] may have always been a trace component with a partial pressure not exceeding 0.1 micropascal (μPa).[13]

Rock-strewn surface imaged by Mars Pathfinder (July 4, 1997)

One oxygen-(O2)-independent process involves a direct chemical reaction of ferrous iron (Fe2+) (commonly present in typical igneous minerals) or metallic iron (Fe) with water (H2O) to produce ferric iron (Fe3+(aq)), which typically leads to hydroxides such as goethite (FeO•OH)[12] under experimental conditions.[14] While this reaction with water (H2O) is thermodynamically disfavored, it may be sustained nevertheless, by the rapid loss of the molecular hydrogen (H2) byproduct.[13] The reaction can be further facilitated by dissolved carbon dioxide (CO2) and sulfur dioxide (SO2), which lower the pH of brine films increasing the concentration of the more oxidative hydrogen ions (H+).[14]

However, higher temperatures (c. 300 °C) are usually needed to decompose Fe3+ (oxy)hydroxides such as goethite into hematite. The formation of palagonitic tephra on the upper slopes of the Mauna Kea volcano may mirror such processes, as consistent with the intriguing spectral and magnetic similarities between palagonitic tephra and Martian dust.[15] In spite of the need for such kinetic conditions, prolonged arid and low pH conditions on Mars (such as diurnal brine films) may lead to the eventual transformation of goethite into hematite given the thermodynamic stability of the latter.[14]

Fe and Fe2+ may also be oxidized by the activity of hydrogen peroxide (H2O2). Even though the H2O2 abundance in the Martian atmosphere is very low,[13] it is temporally persistent and a much stronger oxidant than H2O. H2O2-driven oxidation to Fe3+ (usually as hydrated minerals), has been observed experimentally.[14] In addition, the pervasiveness of the α-Fe2O3 spectral signature, but not of hydrated Fe3+ minerals reinforces the possibility that npOx may form even without the thermodynamically disfavored intermediaries such as goethite.[6]

There is also evidence that hematite might form from magnetite in the course of erosion processes. Experiments at the Mars Simulation Laboratory of Aarhus University in Denmark show that when a mixture of magnetite powder, quartz sand, and quartz dust particles is tumbled in a flask, some of the magnetite converts to hematite, coloring the sample red. The proposed explanation for this effect is that when quartz is fractured by the grinding, certain chemical bonds get broken at the newly exposed surfaces; when these surfaces come in contact with magnetite, oxygen atoms may be transferred from quartz surface to magnetite, forming hematite.[16]

## Red skies on Mars

Approximately true-colour images from the Mars Pathfinder and Mars Exploration Rover missions indicate that the Martian sky may also appear reddish to humans. Absorption of sunlight in the 0.4-0.6 μm range by dust particles may be the primary reason for the redness of the sky.[17] An additional contribution may come from the dominance of photon scattering by dust particles at wavelengths in the order 3 μm,[4] which is in the near-infrared range, over Rayleigh scattering by gas molecules.[18]

## References

1. ↑ 1.0 1.1 1.2 "Mars in a minute: Is Mars really red?". https://science.nasa.gov/resource/mars-in-a-minute-is-mars-really-red/.
2. ↑ 2.0 2.1 Kieffer, Hugh H., Bruce M. Jakosky, and Conway W. Snyder (1992), "The planet Mars: From antiquity to the present," in Mars, University of Arizona Press, Tucson, AZ, p. 2 [1] ISBN 0-8165-1257-4
3. ↑ Fergason et al. (11 February 2006). "Physical properties of the Mars Exploration Rover landing sites as inferred from Mini-TES–derived thermal inertia". Journal of Geophysical Research 111 (E2): n/a. doi:10.1029/2005JE002583. Bibcode: 2006JGRE..111.2S21F.
4. ↑ 4.0 4.1 Lemmon et al. (3 December 2004). "Atmospheric Imaging Results from the Mars Exploration Rovers: Spirit and Opportunity". Science 306 (5702): 1753–1756. doi:10.1126/science.1104474. PMID 15576613. Bibcode: 2004Sci...306.1753L.
5. ↑ Ruff; Christensen (11 December 2002). "Bright and dark regions on Mars: Particle size and mineralogical characteristics based on Thermal Emission Spectrometer data". Journal of Geophysical Research 107 (E12): 2–1–2–22. doi:10.1029/2001JE001580. Bibcode: 2002JGRE..107.5127R.
6. ↑ 6.0 6.1 Bibring et al. (21 April 2006). "Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data". Science 312 (5772): 400–404. doi:10.1126/science.1122659. PMID 16627738. Bibcode: 2006Sci...312..400B.
7. ↑ Poulet et al. (18 July 2007). "Martian surface mineralogy from Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité on board the Mars Express spacecraft (OMEGA/MEx): Global mineral maps". Journal of Geophysical Research 112 (E8): E08S02. doi:10.1029/2006JE002840. Bibcode: 2007JGRE..112.8S02P.
8. ↑ Goetz; Madsen; Hviid. "The nature of Martian airborne dust. Indication of long-lasting dry periods on the surface of Mars.". Seventh International Conference on Mars. https://www.lpi.usra.edu/meetings/7thmars2007/pdf/3104.pdf. Retrieved 2017-11-12.
9. ↑ "Magnetite". mindat.org. http://www.mindat.org/min-2538.html.
10. ↑ 10.0 10.1 Yen et al. (7 July 2005). "An integrated view of the chemistry and mineralogy of martian soils". Nature 436 (7047): 49–54. doi:10.1038/nature03637. PMID 16001059. Bibcode: 2005Natur.436...49Y.
11. ↑ 11.0 11.1 Hamilton et al. (7 December 2005). "Mineralogy of Martian atmospheric dust inferred from thermal infrared spectra of aerosols". Journal of Geophysical Research 110 (E12): E12006. doi:10.1029/2005JE002501. Bibcode: 2005JGRE..11012006H.
12. ↑ 12.0 12.1 Catling; Moore (October 2003). "The nature of coarse-grained crystalline hematite and its implications for the early environment of Mars". Science 165 (2): 277–300. doi:10.1016/S0019-1035(03)00173-8. Bibcode: 2003Icar..165..277C.
13. ↑ 13.0 13.1 13.2 Chevrier et al. (5 July 2007). "Early geochemical environment of Mars as determined from thermodynamics of phyllosilicates". Nature 448 (7149): 60–63. doi:10.1038/nature05961. PMID 17611538. Bibcode: 2007Natur.448...60C.
14. ↑ 14.0 14.1 14.2 14.3 Chevrier et al. (15 August 2006). "Iron weathering products in a CO2 + (H2O or H2O2) atmosphere: Implications for weathering processes on the surface of Mars". Geochimica et Cosmochimica Acta 70 (16): 4295–4317. doi:10.1016/j.gca.2006.06.1368. Bibcode: 2006GeCoA..70.4295C.
15. ↑ Morris et al. (1 March 2001). "Phyllosilicate-poor palagonitic dust from Mauna Kea Volcano (Hawaii): A mineralogical analogue for magnetic Martian dust?". Journal of Geophysical Research 106 (E3): 5057–5083. doi:10.1029/2000JE001328. Bibcode: 2001JGR...106.5057M.
16. ↑ Moskowitz, Clara (September 2009). "How Mars Turned Red: Surprising New Theory". Yahoo News. https://news.yahoo.com/s/space/20090921/sc_space/howmarsturnedredsurprisingnewtheory.
17. ↑ Bell III et al. (28 September 2006). "Chromaticity of the Martian sky as observed by the Mars Exploration Rover Pancam instruments". Journal of Geophysical Research 111 (E12): n/a. doi:10.1029/2006JE002687. Bibcode: 2006JGRE..11112S05B.
18. ↑ Thomas et al. (1 April 1999). "The color of the Martian sky and its influence on the illumination of the Martian surface". Journal of Geophysical Research 104 (E4): 8795–8808. doi:10.1029/98JE02556. Bibcode: 1999JGR...104.8795T.

## External links

* NASA - Mars in a Minute: Is Mars Really Red?
* ContactInContext - Mars, The "Golden Brown" (not Red) Planet?

* v
* t
* e

Geography of Mars and geology of Mars

Cartography

| Regions|

* Abalos Undae
* Aspledon Undae
* Arabia Terra
* Cerberus
* Cydonia
* Eridania Lake
* Hyperboreae Undae
* Ogygis Undae
* Olympia Undae
* Planum Australe
* Planum Boreum
* Quadrangles
* Sinus Meridiani
* Siton Undae
* Tempe Terra
* Terra Cimmeria
* Terra Sabaea
* Tharsis
* Vastitas Borealis

|

Quadrangles|

* Aeolis
* Amazonis
* Amenthes
* Arabia
* Arcadia
* Argyre
* Casius
* Cebrenia
* Coprates
* Diacria
* Elysium
* Eridania
* Hellas
* Iapygia
* Ismenius Lacus
* Lunae Palus
* Mare Acidalium
* Mare Australe (South Pole)
* Mare Boreum (North Pole)
* Mare Tyrrhenum
* Margaritifer Sinus
* Memnonia
* Noachis
* Oxia Palus
* Phaethontis
* Phoenicis Lacus
* Sinus Sabaeus
* Syrtis Major
* Tharsis
* Thaumasia

Geology

| Surface features|

* Brain terrain
* Carbonates
* Chaos terrain
* Color
* Composition
* Concentric crater fill
* Dark slope streak
* Dichotomy
* Dune fields
* Hagal
* Nili Patera
* Fretted terrain
* Geysers
* Glaciers
* Groundwater
* Gullies
* Inverted relief
* Lakes
* Lava tubes
* Lineated valley fill (LVF)
* Lobate debris apron
* North Polar Basin
* Ocean hypothesis
* Ore resources
* Outflow channels
* Polar caps
* Ring mold craters
* Rootless cones
* Scalloped topography
* Seasonal flows
* Soil
* Spherules
* Surface
* Swiss cheese features
* Terrain softening
* Tholus
* Upper plains unit
* Valley networks
* Water
* Yardangs

|

History|

* Amazonian
* Hesperian
* Noachian
* Volcanology
* Observation history
* Canals (list)
* Classical albedo features

Rocks observed|

* Curiosity rover
* Bathurst Inlet
* Coronation
* Goulburn
* Hottah
* Jake Matijevic
* Link
* Rocknest
* Rocknest 3
* Tintina
* Opportunity rover
* Bounce
* El Capitan
* Last Chance
* Sojourner rover
* Barnacle Bill
* Yogi
* Spirit rover
* Adirondack
* Home Plate
* Mimi
* Pot of Gold
* Viking
* Big Joe
* Other
* Face
* Monolith

* Meteorites found on Mars
* Block Island
* Heat Shield
* Mackinac Island
* Meridiani Planum
* Oileán Ruaidh
* Shelter Island

* Martian meteorites found on Earth
* Balsaltic Breccia
* Chassignites
* Nakhlites
* Shergottites
* Other
* List

Topography

| Mountains and
volcanoes

(list by height)

* Acidalia Colles
* Alba Mons
* Anseris Mons
* Apollinaris Mons
* Ariadnes Colles
* Astapus Colles
* Ausonia Montes
* Avernus Colles
* Biblis Tholus
* Centauri Montes
* Charitum Montes
* Echus Montes
* Elysium
* Elysium Mons
* Albor Tholus
* Hecates Tholus
* Erebus Montes
* Galaxius Mons
* Hadriacus Mons
* Hellas Montes
* Jovis Tholus
* Libya Montes
* Mount Sharp
* Nereidum Montes
* Olympus Mons
* Phlegra Montes
* Syrtis Major Planum
* Tartarus Colles
* Tartarus Montes
* Tharsis Montes
* Ascraeus
* Pavonis
* Arsia
* Tharsis Tholus
* Tyrrhenus Mons
* Ulysses Tholus
* Uranius group
* Uranius Mons
* Ceraunius Tholus
* Uranius Tholus

|

Plains and
plateaus|

* Acidalia Planitia
* Aeolis Palus
* Amazonis Planitia
* Arcadia Planitia
* Argyre Planitia
* Chryse Planitia
* Daedalia Planum
* Elysium Planitia
* Eridania Planitia
* Hellas Planitia
* Hesperia Planum
* Icaria Planum
* Isidis Planitia
* Lunae Planum
* Meridiani Planum
* Oxia Planum
* Planum Australe
* Planum Boreum
* Syria Planum
* Syrtis Major Planum
* Utopia Planitia
* Eden Patera
* Orcus Patera
* Peneus Patera
* Pityusa Patera

Canyons and
valleys|

* Aram Chaos
* Arsia Chasmata
* Aromatum Chaos
* Atlantis Chaos
* Aureum Chaos
* Candor Chasma
* Chasma Boreale
* Coprates Chasma
* Echus Chasma
* Eos Chaos
* Eos Chasma
* Galaxias Chaos
* Ganges Chasma
* Gorgonum Chaos
* Hebes Chasma
* Hydaspis Chaos
* Hydraotes Chaos
* Iani Chaos
* Ister Chaos
* Ius Chasma
* Juventae Chasma
* Melas Chasma
* Ophir Chasma
* Tithonium Chasma

* List of valles
* Apsus
* Ares
* Arnus
* Asopus
* Athabasca
* Auqakuh
* Bahram
* Buvinda
* Dao
* Enipeus
* Frento
* Granicus
* Green Valley
* Harmakhis
* Hebrus
* Her Desher
* Hrad
* Huo Hsing
* Hypanis
* Iberus
* Indus
* Ituxi
* Kasei
* Labou
* Ladon
* Lethe
* Licus
* Louros
* Ma'adam
* Mad
* Maja
* Mamers
* Mangala
* Marineris
* Labes
* Marte
* Maumee
* Mawrth
* Minio
* Naktong
* Nanedi
* Niger
* Nirgal
* Padus
* Paraná
* Patapsco
* Peace
* Rahway
* Ravi
* Reull
* Sabis
* Sabrina
* Samara
* Scamander
* Shalbatana
* Simud
* Stura
* Tader
* Tinia
* Tinjar
* Tiu
* Tyras
* Uzboi
* ULM
* Vedra
* Verde
* Warrego

Fossae, mensae
rupes and labyrinthi|

* Amenthes Fossae
* Ceraunius Fossae
* Cerberus Fossae
* Coloe Fossae
* Cyane Fossae
* Elysium Fossae
* Hephaestus Fossae
* Icaria Fossae
* Labeatis Fossae
* Mangala Fossa
* Mareotis Fossae
* Medusae Fossae
* Memnonia Fossae
* Nili Fossae
* Olympica Fossae
* Oti Fossae
* Sirenum Fossae
* Tantalus Fossae
* Tempe Fossae
* Tithonium Fossae
* Tractus Fossae
* Ulysses Fossae
* Aeolis Mensae
* Ausonia Mensa
* Capri Mensa
* Cydonia Mensae
* Deuteronilus Mensae
* Ganges Mensa
* Nilosyrtis Mensae
* Protonilus Mensae
* Sacra Mensa
* Claritas Rupes
* Olympus Rupes
* Rupes Tenuis
* Angustus Labyrinthus
* Noctis Labyrinthus

Catenae and
craters|

* Artynia Catena
* Tithoniae Catenae
* Tractus Catena
* Adams
* Agassiz
* Airy
* Airy-0
* Aniak
* Antoniadi
* Arandas
* Argo
* Arkhangelsky
* Arrhenius
* Asimov
* Bacolor
* Bakhuysen
* Baldet
* Baltisk
* Bamberg
* Barabashov
* Barnard
* Beagle
* Becquerel
* Beer
* Belz
* Bernard
* Bianchini
* Boeddicker
* Bok
* Bond
* Bonestell
* Bonneville
* Brashear
* Briault
* Burroughs
* Burton
* Campbell
* Canso
* Cassini
* Caxias
* Cerulli
* Chafe
* Chapais
* Chincoteague
* Chryse Alien
* Clark
* Coblentz
* Columbus
* Copernicus
* Corby
* Crewe
* Crivitz
* Crommelin
* Cruls
* Curie
* Da Vinci
* Danielson
* Darwin
* Davies
* Dawes
* Dejnev
* Denning
* Dilly
* Dinorwic
* Douglass
* Dromore
* Du Martheray
* Eagle
* Eberswalde
* Eddie
* Ejriksson
* Emma Dean
* Endeavour
* Matijevic Hill
* Endurance
* Erebus
* Escalante
* Eudoxus
* Fenagh
* Fesenkov
* Firsoff
* Flammarion
* Flaugergues
* Focas
* Fontana
* Fournier
* Fram
* Galdakao
* Gale
* Galle
* Garni
* Gasa
* Gilbert
* Gill
* Gledhill
* Gold
* Graff
* Green
* Grindavik
* Gusev
* Apollo 1 Hills
* Chaffee
* Grissom
* White
* Columbia Hills
* Husband
* McCool
* Sleepy Hollow
* Hadley
* Haldane
* Hale
* Halley
* Hartwig
* Heaviside
* Heimdal
* Heinlein
* Helmholtz
* Henry
* Herschel
* Hipparchus
* Holden
* Holmes
* Hooke
* Huggins
* Hussey
* Hutton
* Huxley
* Huygens
* Iazu
* Ibragimov
* Inuvik
* Janssen
* Jarry-Desloges
* Jeans
* Jezero
* Jezža
* Joly
* Jones
* Kaiser
* Keeler
* Kepler
* Kinkora
* Kipini
* Knobel
* Koga
* Korolev
* Kufra
* Kuiper
* Kunowsky
* Lambert
* Lamont
* Lampland
* Lassell
* Lau
* Le Verrier
* Li Fan
* Liais
* Lipik
* Liu Hsin
* Llanesco
* Lockyer
* Lod
* Lohse
* Lomonosov
* Lowell
* Lyell
* Lyot
* Mädler
* Magelhaens
* Maggini
* Main
* Mandora
* Maraldi
* Mariner
* Marth
* Martz
* Masursky
* Maunder
* McLaughlin
* McMurdo
* Mellish
* Mendel
* Mie
* Milankovic
* Millochau
* Mitchel
* Miyamoto
* Mohawk
* Mojave
* Molesworth
* Montevallo
* Moreux
* Müller
* Nansen
* Nereus
* Newton
* Nhill
* Nicholson
* Niesten
* Nipigon
* Onon
* Orson Welles
* Oudemans
* Palana
* Pangboche
* Pasteur
* Penticton
* Perepelkin
* Peridier
* Persbo
* Pettit
* Phillips
* Pickering
* Playfair
* Pollack
* Poona
* Porter
* Porth
* Priestley
* Proctor
* Ptolemaeus
* Puńsk
* Quenisset
* Rabe
* Radau
* Rahe
* Rayleigh
* Redi
* Renaudot
* Reuyl
* Reynolds
* Richardson
* Ritchey
* Robert Sharp
* Roddenberry
* Ross
* Rossby
* Rudaux
* Russell
* Rutherford
* Sagan
* Saheki
* Santa Maria
* Schaeberle
* Schiaparelli
* Schmidt
* Secchi
* Semeykin
* Sharonov
* Sibu
* Sinton
* Sitka
* Sklodowska
* Slipher
* Smith
* South
* Spallanzani
* Srīpur
* Steno
* Stokes
* Stoney
* Suess
* Suzhi
* Tarsus
* Taytay
* Teisserenc de Bort
* Terby
* Thila
* Thira
* Tikhonravov
* Tikhov
* Timbuktu
* Tombaugh
* Tooting
* Trouvelot
* Troy
* Trud
* Trumpler
* Tugaske
* Tycho Brahe
* Tyndall
* Udzha
* Vernal
* Very
* Victoria
* Cape Verde
* Vinogradov
* Vinogradsky
* Virrat
* Vishniac
* Vogel
* Von Kármán
* Wallace
* Wegener
* Weinbaum
* Wells
* Williams
* Winslow
* Wirtz
* Wislicenus
* Wright
* Yuty
* Zumba
* Zunil

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