Formation of the hematite-bearing unit in Meridiani Planum: Evidence for deposition in standing water

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Abstract

The most plausible models for the origin and evolution of a unique geologic unit in Meridiani Planum, Mars, are low-temperature precipitation of Fe oxides/oxyhydroxides from standing water, precipitation from circulating fluids of hydrothermal origin, or the thermal oxidation of magnetite-rich ash. Analysis of Odyssey Thermal Emission Imaging System (THEMIS) infrared and visible images, together with MGS TES, MOLA, and MOC data, has provided additional insight into the Meridiani region. The hematite at Meridiani was most likely derived from a Fe oxyhydroxide precursor such as goethite, is mixed with basalt as the major component, occurs as a thin layer meters to <200 m thick, and is thermophysically distinct from units immediately above and below. Remnants of a hematite-poor unit lie directly above the hematite layer, indicating that hematite formation was sharply confined vertically. The hematite unit appears to embay preexisting channels and occurs only as outliers within closed crater basins, suggesting that it was deposited in a gravity-driven fluid, rather than as a dispersed air fall. The hematite unit lies within a topographic trough over ∼3/4 of its circumference, with the remaining perimeter <150 m lower in elevation. Oxidation of ash during emplacement is unlikely given a goethite precursor and basalt as the major component. Hydrothermal alteration does not account for the confined vertical extent of the hematite layer over large distances and across disconnected outliers. The preferred model is the deposition of hematite or precursor Fe oxyhydroxides in water-filled basins, followed by dehydroxylation to hematite in low-temperature diagenesis. This model accounts for (1) the uniform deposition of a thin hematite-bearing unit over an area ∼150,000 km 2 in size; (2) the transition from hematite-rich to hematite-poor units over less than ∼10 m vertical distance; (3) the distinct differences from the underlying layers; (4) goethite as the precursor to hematite; (5) the embayment relationships; (6) the occurrence of remnants of the hematite-bearing unit in isolated craters surrounding the main deposit; (7) the lack of other hydrothermal minerals; and (8) the presence of coarse-grained, low-albedo basalt, rather than ash, as the major component. The occurrence of unweathered olivine, pyroxene, and feldspar throughout the equatorial region provides strong evidence that extensive aqueous weathering has not occurred on Mars. Thus the presence of a small number of bodies of standing water appears to represent brief, localized phenomena set against the backdrop of a cold, frozen planet.

Original languageEnglish (US)
JournalJournal of Geophysical Research E: Planets
Volume109
Issue number8
DOIs
StatePublished - Aug 25 2004

Fingerprint

Bearings (structural)
Temazepam
hematite
Water
water
Ashes
ashes
goethite
basalt
ash
ferric oxide
outlier
craters
mars
crater
Mars
occurrences
Ferrosoferric Oxide
dehydroxylation
Mars Global Surveyor

Keywords

  • Hematite
  • Meridiani
  • Standing water

ASJC Scopus subject areas

  • Oceanography
  • Astronomy and Astrophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Geophysics
  • Geochemistry and Petrology

Cite this

@article{e48e5b14f2db4f188105c7bf84dbbb16,
title = "Formation of the hematite-bearing unit in Meridiani Planum: Evidence for deposition in standing water",
abstract = "The most plausible models for the origin and evolution of a unique geologic unit in Meridiani Planum, Mars, are low-temperature precipitation of Fe oxides/oxyhydroxides from standing water, precipitation from circulating fluids of hydrothermal origin, or the thermal oxidation of magnetite-rich ash. Analysis of Odyssey Thermal Emission Imaging System (THEMIS) infrared and visible images, together with MGS TES, MOLA, and MOC data, has provided additional insight into the Meridiani region. The hematite at Meridiani was most likely derived from a Fe oxyhydroxide precursor such as goethite, is mixed with basalt as the major component, occurs as a thin layer meters to <200 m thick, and is thermophysically distinct from units immediately above and below. Remnants of a hematite-poor unit lie directly above the hematite layer, indicating that hematite formation was sharply confined vertically. The hematite unit appears to embay preexisting channels and occurs only as outliers within closed crater basins, suggesting that it was deposited in a gravity-driven fluid, rather than as a dispersed air fall. The hematite unit lies within a topographic trough over ∼3/4 of its circumference, with the remaining perimeter <150 m lower in elevation. Oxidation of ash during emplacement is unlikely given a goethite precursor and basalt as the major component. Hydrothermal alteration does not account for the confined vertical extent of the hematite layer over large distances and across disconnected outliers. The preferred model is the deposition of hematite or precursor Fe oxyhydroxides in water-filled basins, followed by dehydroxylation to hematite in low-temperature diagenesis. This model accounts for (1) the uniform deposition of a thin hematite-bearing unit over an area ∼150,000 km 2 in size; (2) the transition from hematite-rich to hematite-poor units over less than ∼10 m vertical distance; (3) the distinct differences from the underlying layers; (4) goethite as the precursor to hematite; (5) the embayment relationships; (6) the occurrence of remnants of the hematite-bearing unit in isolated craters surrounding the main deposit; (7) the lack of other hydrothermal minerals; and (8) the presence of coarse-grained, low-albedo basalt, rather than ash, as the major component. The occurrence of unweathered olivine, pyroxene, and feldspar throughout the equatorial region provides strong evidence that extensive aqueous weathering has not occurred on Mars. Thus the presence of a small number of bodies of standing water appears to represent brief, localized phenomena set against the backdrop of a cold, frozen planet.",
keywords = "Hematite, Meridiani, Standing water",
author = "Philip Christensen and Steven Ruff",
year = "2004",
month = "8",
day = "25",
doi = "10.1029/2003JE002233",
language = "English (US)",
volume = "109",
journal = "Journal of Geophysical Research: Atmospheres",
issn = "2169-897X",
publisher = "Wiley-Blackwell",
number = "8",

}

TY - JOUR

T1 - Formation of the hematite-bearing unit in Meridiani Planum

T2 - Evidence for deposition in standing water

AU - Christensen, Philip

AU - Ruff, Steven

PY - 2004/8/25

Y1 - 2004/8/25

N2 - The most plausible models for the origin and evolution of a unique geologic unit in Meridiani Planum, Mars, are low-temperature precipitation of Fe oxides/oxyhydroxides from standing water, precipitation from circulating fluids of hydrothermal origin, or the thermal oxidation of magnetite-rich ash. Analysis of Odyssey Thermal Emission Imaging System (THEMIS) infrared and visible images, together with MGS TES, MOLA, and MOC data, has provided additional insight into the Meridiani region. The hematite at Meridiani was most likely derived from a Fe oxyhydroxide precursor such as goethite, is mixed with basalt as the major component, occurs as a thin layer meters to <200 m thick, and is thermophysically distinct from units immediately above and below. Remnants of a hematite-poor unit lie directly above the hematite layer, indicating that hematite formation was sharply confined vertically. The hematite unit appears to embay preexisting channels and occurs only as outliers within closed crater basins, suggesting that it was deposited in a gravity-driven fluid, rather than as a dispersed air fall. The hematite unit lies within a topographic trough over ∼3/4 of its circumference, with the remaining perimeter <150 m lower in elevation. Oxidation of ash during emplacement is unlikely given a goethite precursor and basalt as the major component. Hydrothermal alteration does not account for the confined vertical extent of the hematite layer over large distances and across disconnected outliers. The preferred model is the deposition of hematite or precursor Fe oxyhydroxides in water-filled basins, followed by dehydroxylation to hematite in low-temperature diagenesis. This model accounts for (1) the uniform deposition of a thin hematite-bearing unit over an area ∼150,000 km 2 in size; (2) the transition from hematite-rich to hematite-poor units over less than ∼10 m vertical distance; (3) the distinct differences from the underlying layers; (4) goethite as the precursor to hematite; (5) the embayment relationships; (6) the occurrence of remnants of the hematite-bearing unit in isolated craters surrounding the main deposit; (7) the lack of other hydrothermal minerals; and (8) the presence of coarse-grained, low-albedo basalt, rather than ash, as the major component. The occurrence of unweathered olivine, pyroxene, and feldspar throughout the equatorial region provides strong evidence that extensive aqueous weathering has not occurred on Mars. Thus the presence of a small number of bodies of standing water appears to represent brief, localized phenomena set against the backdrop of a cold, frozen planet.

AB - The most plausible models for the origin and evolution of a unique geologic unit in Meridiani Planum, Mars, are low-temperature precipitation of Fe oxides/oxyhydroxides from standing water, precipitation from circulating fluids of hydrothermal origin, or the thermal oxidation of magnetite-rich ash. Analysis of Odyssey Thermal Emission Imaging System (THEMIS) infrared and visible images, together with MGS TES, MOLA, and MOC data, has provided additional insight into the Meridiani region. The hematite at Meridiani was most likely derived from a Fe oxyhydroxide precursor such as goethite, is mixed with basalt as the major component, occurs as a thin layer meters to <200 m thick, and is thermophysically distinct from units immediately above and below. Remnants of a hematite-poor unit lie directly above the hematite layer, indicating that hematite formation was sharply confined vertically. The hematite unit appears to embay preexisting channels and occurs only as outliers within closed crater basins, suggesting that it was deposited in a gravity-driven fluid, rather than as a dispersed air fall. The hematite unit lies within a topographic trough over ∼3/4 of its circumference, with the remaining perimeter <150 m lower in elevation. Oxidation of ash during emplacement is unlikely given a goethite precursor and basalt as the major component. Hydrothermal alteration does not account for the confined vertical extent of the hematite layer over large distances and across disconnected outliers. The preferred model is the deposition of hematite or precursor Fe oxyhydroxides in water-filled basins, followed by dehydroxylation to hematite in low-temperature diagenesis. This model accounts for (1) the uniform deposition of a thin hematite-bearing unit over an area ∼150,000 km 2 in size; (2) the transition from hematite-rich to hematite-poor units over less than ∼10 m vertical distance; (3) the distinct differences from the underlying layers; (4) goethite as the precursor to hematite; (5) the embayment relationships; (6) the occurrence of remnants of the hematite-bearing unit in isolated craters surrounding the main deposit; (7) the lack of other hydrothermal minerals; and (8) the presence of coarse-grained, low-albedo basalt, rather than ash, as the major component. The occurrence of unweathered olivine, pyroxene, and feldspar throughout the equatorial region provides strong evidence that extensive aqueous weathering has not occurred on Mars. Thus the presence of a small number of bodies of standing water appears to represent brief, localized phenomena set against the backdrop of a cold, frozen planet.

KW - Hematite

KW - Meridiani

KW - Standing water

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U2 - 10.1029/2003JE002233

DO - 10.1029/2003JE002233

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JO - Journal of Geophysical Research: Atmospheres

JF - Journal of Geophysical Research: Atmospheres

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