Download Mineralogy of the Martian Surface

Mineralogy of the
Martian Surface
Bethany Ehlmann and Christopher Edwards
 Using the emissivity spectrum from a pure
material it is easy to identify its
composition.
 Emissivity spectra from the individual
components of a mixture add together in a
linear fashion.
 Rock spectra must first be unmixed or
deconvolved by comparing the features of
the spectrum to those of the endmemer
spectra from a library.
 Individual components of the mixture are
identified by matching its spectrum to
those in the library.
 Using this technique we are also able to
determine the relative amounts present
Surface age
Figure 2
a) Global olivine distribution from TES and OMEGA. The purple to green tones are the total olivine
abundances for all compositions derived from TES deconvolution results.Yellow to red tones are
olivine spectral indicies, correlated with 1-um absorption band strength and derived from OMEGA
data for locations where olivine was detected
 TIR and VNIR of dust free southern highlands indicates a basaltic
crust
Primary
Igneous
Mineralogy
 Local variation is present due to fractional crystallization and
crustal assimilation
 Surface can be grouped into distinctive types based on mineral
proportions (olivine, Cpx, Opx, feldspars, etc.)
 Plag. And Cpx are the dominant minerals of most of the southern
highlands
 Northern plains have the lowest Pyx abundance and highest
concentration of silica phases.
Figure 3.
a) Location of the Nili Patera caldera
on a topographic hillshade map.
(b)Yellow tones identify a late-stage
dacite lava flow (white arrow), likely
formed by differentiation of
magmas. Magenta/ purple tones
identify olivine-bearing deposits.
(c) Small deposits of hydrated silica
( yellow arrows) identified by CRISM
on and around the volcanic cone
formed during the Hesperian or
later from alteration by volcanic
vapors and/or waters (Skok et al.
2010).
 Product of local bedrock compositions
 Local variation in sands and soils are found throughout mars.
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Sands and
Soils
Generally regolith material appears olivine depleted
Olivine rich sands in Nili Fosse
Course Olivine sands in Columbia hills
Hematite grains sands are derived from weathering in Meridiani
Rock-water interactions has produced gypsum dunes in the northern
lowlands
 Mars dust appears to be an alteration product
 VNIR data shows a strong Fe3+ absorption
 VNIR and TIR data show that dusty surfaces are hydrated silicates
 Using TES lofted dust has been sampled and is dominantly Plag, and
hydrated silicates, with lesser amounts of olivine, Pyx, and sulfates
Collectively this data show that the dust is a product of weathering
of primary rocks along with oxidation and limited exposure to liquid
water
Secondary
Alteration of
the Crust
 Global widespread occurrence of hydrated silicates
Hydration and
Alteration of
the crust
 High resolution orbital data has shown exposures are small but
widespread. We have observed phylosilicates…
 In stratigraphic units possible due to in-situ alteration
 Associated with impact craters (central peaks, walls, ejecta)
 As deposits in sedimentary basins
 CRISM data overlain HiRISE image
 Aluminum phyllosilicates overlie nontronite-bearing
sediments at Mawrth Vallis.
 Outcrops similar to this have been observed in Nili Fosse,
Vallis Marineris, and in numerous small outcrops across the
southern highlands.
 These may be the result of acid alteration and/or leaching
later in Mars history.
Scale bar indicates 200m
 Impact craters have provided exposure of the deep
Noachian crust.
 Fe/Mg smectites are common throughout many craters
 Some also contain chlorite minerals as well prehnite and
illite.
 This assemblage indicates a high temperature hydrothermal
system
 The location of these minerals throughout the crater as well
as in the central peak and ejecta blanket indicate that the
hydrothermal alteration preceded the impact
Paleolakes
 Clear relationship between predicted groundwater upwelling &
orbital detections of sulfate minerals.
Groundwater,
Sulfates, and
Ferric Oxides
 Hesperian sedimentary rocks with hematite and hydrated sulfates
overlie Noachian units with phylosilicates.
 Vugs and spherical nodules of hematite are evidence of multiple
episodes of groundwater upwelling and precipitation.
 The presence of Jarosite and alunite in some of these basins
indicates acidic waters with a ph<4
Secondary
Alteration of
the Crust
 CRISM image
 Upper capping rock
unit (purple) is sitting
atop olvine bearing
units (yellow) and
clays (blue). Where
olivine units have
greenish coloration is
indicative of
carbonate formation
within the olivine
stratigraphy.
Carbonates
Image Credit: NASA/JPL/JHUAPL
/MSSS/Brown University
20 KM
 Oldest Noachian crust is basaltic, it is unknown if any examples of
the Primary crust have survived till today
 Extensive examples of phyllosilicates and aqueous altered
minerals present in much of the older Noachian crust.
 Some aqueous alteration seen into the Hesperian, evidence for a
more acid environment.
Conclusions
 Paleolakes existed in the late Noachian to early Hesperian. Some
basins host sedimentary clay and precipitated salts.
 Ground water played an important role in formation of clay
minerals. Upwelling of groundwater has produced large deposits
of sulfates, and hematite.
 Amazonian units do not have crystalline alteration minerals,
implying substantially less water
References
 Ehlmann, B. L., & Edwards, C. S. (2014). Mineralogy of the Martian
Surface. Annual Review of Earth and Planetary Sciences, 42(1),
291–315. http://doi.org/10.1146/annurev-earth-060313-055024
 http://www.sfgate.com/news/article/Mars-carbonates-point-towatery-environment-3180406.php