Mars surface color

Last updated
Yogi Rock, analyzed by the Sojourner rover (July 4, 1997) Pathfinder01.jpg
Yogi Rock, analyzed by the Sojourner rover (July 4, 1997)

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]

Contents

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]

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 m (7 feet) 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). PIA17944-MarsCuriosityRover-AfterCrossingDingoGapSanddune-20140209.jpg
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) Mars rocks.jpg
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 in situ 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]

Related Research Articles

<span class="mw-page-title-main">Hematite</span> Common iron oxide mineral

Hematite, also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe
2O
3. It has the same crystal structure as corundum (Al
2O
3) and ilmenite (FeTiO
3). With this it forms a complete solid solution at temperatures above 950 °C (1,740 °F).

<span class="mw-page-title-main">Mars Exploration Rover</span> NASA mission to explore Mars via two rovers

NASA's Mars Exploration Rover (MER) mission was a robotic space mission involving two Mars rovers, Spirit and Opportunity, exploring the planet Mars. It began in 2003 with the launch of the two rovers to explore the Martian surface and geology; both landed on Mars at separate locations in January 2004. Both rovers far outlived their planned missions of 90 Martian solar days: MER-A Spirit was active until March 22, 2010, while MER-B Opportunity was active until June 10, 2018.

<span class="mw-page-title-main">Wüstite</span> Iron(II) oxide mineral formed under reducing conditions

Wüstite is a mineral form of mostly iron(II) oxide found with meteorites and native iron. It has a grey colour with a greenish tint in reflected light. Wüstite crystallizes in the isometric-hexoctahedral crystal system in opaque to translucent metallic grains. It has a Mohs hardness of 5 to 5.5 and a specific gravity of 5.88. Wüstite is a typical example of a non-stoichiometric compound.

<span class="mw-page-title-main">Gusev (Martian crater)</span> Crater on Mars

Gusev is a crater on the planet Mars and is located at 14.5°S 175.4°E and is in the Aeolis quadrangle. The crater is about 166 kilometers in diameter and formed approximately three to four billion years ago. It was named after Russian astronomer Matvey Gusev (1826–1866) in 1976.

<span class="mw-page-title-main">Meridiani Planum</span> Plain located 2 degrees south of Mars equator

The Meridiani Planum (alternately Meridiani plain, Meridiani plains, Terra Meridiani, or Terra Meridiani plains) is either a large plain straddling the equator of Mars and covered with a vast number of spherules containing a lot of iron oxide or a region centered on this plain that includes some adjoining land. The plain sits on top of an enormous body of sediments that contains a lot of bound water. The iron oxide in the spherules is crystalline (grey) hematite (Fe203).

<span class="mw-page-title-main">Jarosite</span> Alunite supergroup, potassium iron basic sulfate mineral

Jarosite is a basic hydrous sulfate of potassium and ferric iron (Fe-III) with a chemical formula of KFe3(SO4)2(OH)6. This sulfate mineral is formed in ore deposits by the oxidation of iron sulfides. Jarosite is often produced as a byproduct during the purification and refining of zinc and is also commonly associated with acid mine drainage and acid sulfate soil environments.

<span class="mw-page-title-main">Martian spherules</span> Small iron oxide spherules found on Mars

Martian spherules (also known as hematite spherules, blueberries, & Martian blueberries) are small spherules (roughly spherical pebbles) that are rich in an iron oxide (grey hematite, α-Fe2O3) and are found at Meridiani Planum (a large plain on Mars) in exceedingly large numbers.

<span class="mw-page-title-main">Thermal Emission Spectrometer</span> Instrument on board Mars Global Surveyor.

The Thermal Emission Spectrometer (TES) is an instrument on board Mars Global Surveyor. TES collects two types of data, hyperspectral thermal infrared data from 6 to 50 micrometres (μm) and bolometric visible-NIR measurements. TES has six detectors arranged in a 2x3 array, and each detector has a field of view of approximately 3 × 6 km on the surface of Mars.

<span class="mw-page-title-main">Atmosphere of Mars</span> Layer of gases surrounding planet Mars

The atmosphere of Mars is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.85%), and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and noble gases. The atmosphere of Mars is much thinner than Earth's. The average surface pressure is only about 610 pascals (0.088 psi) which is less than 1% of the Earth's value.

<span class="mw-page-title-main">Scientific information from the Mars Exploration Rover mission</span>

NASA's 2003 Mars Exploration Rover Mission has amassed an enormous amount of scientific information related to the Martian geology and atmosphere, as well as providing some astronomical observations from Mars. This article covers information gathered by the Opportunity rover during the initial phase of its mission. Information on science gathered by Spirit can be found mostly in the Spirit rover article.

<span class="mw-page-title-main">Compact Reconnaissance Imaging Spectrometer for Mars</span> Visible-infrared spectrometer

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) was a visible-infrared spectrometer aboard the Mars Reconnaissance Orbiter searching for mineralogic indications of past and present water on Mars. The CRISM instrument team comprised scientists from over ten universities and was led by principal investigator Scott Murchie. CRISM was designed, built, and tested by the Johns Hopkins University Applied Physics Laboratory.

<span class="mw-page-title-main">Aram Chaos</span> Crater on Mars

Aram Chaos, centered at 2.6°N, 21.5°W, is a heavily eroded impact crater on Mars. It lies at the eastern end of the large canyon Valles Marineris and close to Ares Vallis. Various geological processes have reduced it to a circular area of chaotic terrain. Aram Chaos takes its name from Aram, one of the classical albedo features observed by Giovanni Schiaparelli, who named it after the Biblical land of Aram. Spectroscopic observation from orbit indicates the presence of the mineral hematite, likely a signature of a once aqueous environment.

<span class="mw-page-title-main">Climate of Mars</span> Climate patterns of the terrestrial planet

The climate of Mars has been a topic of scientific curiosity for centuries, in part because it is the only terrestrial planet whose surface can be easily directly observed in detail from the Earth with help from a telescope.

<span class="mw-page-title-main">Mawrth Vallis</span> Valley on Mars

Mawrth Vallis is a valley on Mars, located in the Oxia Palus quadrangle at 22.3°N, 343.5°E with an elevation approximately two kilometers below datum. Situated between the southern highlands and northern lowlands, the valley is a channel formed by massive flooding which occurred in Mars’ ancient past. It is an ancient water outflow channel with light-colored clay-rich rocks.

<span class="mw-page-title-main">Martian soil</span> Fine regolith found on the surface of Mars

Martian soil is the fine regolith found on the surface of Mars. Its properties can differ significantly from those of terrestrial soil, including its toxicity due to the presence of perchlorates. The term Martian soil typically refers to the finer fraction of regolith. So far, no samples have been returned to Earth, the goal of a Mars sample-return mission, but the soil has been studied remotely with the use of Mars rovers and Mars orbiters.

<span class="mw-page-title-main">Water on Mars</span> Study of past and present 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 flowing sand and dust slipping downhill to make dark streaks. While most water ice is buried, it is exposed at the surface across several locations on Mars. In the mid-latitudes, it is exposed by impact craters, steep scarps and gullies. Additionally, water ice is also visible at the surface at the north polar ice cap. Abundant water ice is also present beneath the permanent carbon dioxide ice cap at the Martian south pole. More than 5 million km3 of ice have been detected at or near the surface of Mars, enough to cover the whole planet to a depth of 35 meters (115 ft). Even more ice might be locked away in the deep subsurface.

The mineralogy of Mars is the chemical composition of rocks and soil that encompass the surface of Mars. Various orbital crafts have used spectroscopic methods to identify the signature of some minerals. The planetary landers performed concrete chemical analysis of the soil in rocks to further identify and confirm the presence of other minerals. The only samples of Martian rocks that are on Earth are in the form of meteorites. The elemental and atmospheric composition along with planetary conditions is essential in knowing what minerals can be formed from these base parts.

To date, interplanetary spacecraft have provided abundant evidence of water on Mars, dating back to the Mariner 9 mission, which arrived at Mars in 1971. This article provides a mission by mission breakdown of the discoveries they have made. For a more comprehensive description of evidence for water on Mars today, and the history of water on that planet, see Water on Mars.

<span class="mw-page-title-main">Groundwater on Mars</span> Water held in permeable ground

Rain and snow was a regular occurrence on Mars in the past; especially in the Noachian and early Hesperian epochs. Some moisture entered the ground and formed aquifers. That is, the water went into the ground, seeped down until it reached a formation that would not allow it to penetrate further. Water then accumulated forming a saturated layer. Deep aquifers may still exist.

<span class="mw-page-title-main">Composition of Mars</span> Branch of the geology of Mars

The composition of Mars covers the branch of the geology of Mars that describes the make-up of the planet Mars.

References

  1. 1 2 3 NASA - Mars in a Minute: Is Mars Really Red? (Transcript)
  2. 1 2 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 Archived 2011-06-04 at the Wayback Machine 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. Bibcode:2006JGRE..111.2S21F. CiteSeerX   10.1.1.596.3226 . doi:10.1029/2005JE002583.
  4. 1 2 Lemmon; et al. (3 December 2004). "Atmospheric Imaging Results from the Mars Exploration Rovers: Spirit and Opportunity". Science . 306 (5702): 1753–1756. Bibcode:2004Sci...306.1753L. doi:10.1126/science.1104474. PMID   15576613. S2CID   5645412.
  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. Bibcode:2002JGRE..107.5127R. doi: 10.1029/2001JE001580 .
  6. 1 2 Bibring; et al. (21 April 2006). "Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data". Science . 312 (5772): 400–404. Bibcode:2006Sci...312..400B. doi: 10.1126/science.1122659 . PMID   16627738.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  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. Bibcode:2007JGRE..112.8S02P. doi:10.1029/2006JE002840. S2CID   16963908.
  8. ↑ Goetz; et al. The nature of Martian airborne dust. Indication of long-lasting dry periods on the surface of Mars (PDF). Seventh International Conference on Mars. Retrieved 2017-11-12.
  9. ↑ "Magnetite". mindat.org. Retrieved 2017-11-04.
  10. 1 2 Yen; et al. (7 July 2005). "An integrated view of the chemistry and mineralogy of martian soils". Nature . 436 (7047): 49–54. Bibcode:2005Natur.436...49Y. doi:10.1038/nature03637. PMID   16001059. S2CID   4397731.
  11. 1 2 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. Bibcode:2005JGRE..11012006H. doi:10.1029/2005JE002501.
  12. 1 2 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. Bibcode:2003Icar..165..277C. doi:10.1016/S0019-1035(03)00173-8.
  13. 1 2 3 Chevrier; et al. (5 July 2007). "Early geochemical environment of Mars as determined from thermodynamics of phyllosilicates". Nature . 448 (7149): 60–63. Bibcode:2007Natur.448...60C. doi:10.1038/nature05961. PMID   17611538. S2CID   1595292.
  14. 1 2 3 4 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. Bibcode:2006GeCoA..70.4295C. doi:10.1016/j.gca.2006.06.1368.
  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. Bibcode:2001JGR...106.5057M. doi: 10.1029/2000JE001328 .
  16. ↑ Moskowitz, Clara (September 2009). "How Mars Turned Red: Surprising New Theory". Yahoo News. Archived from the original on September 25, 2009. Retrieved 2009-09-21.
  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. Bibcode:2006JGRE..11112S05B. doi: 10.1029/2006JE002687 .
  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. Bibcode:1999JGR...104.8795T. doi: 10.1029/98JE02556 .
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.