Mössbauer mineralogy of rock, soil, and dust at Gusev crater, Mars: Spirit's journey through weakly altered olivine basalt on the plains and pervasively altered basalt in the Columbia Hills

Abstract

The Mössbauer spectrometer on Spirit measured the oxidation state of Fe, identified Fe‐bearing phases, and measured relative abundances of Fe among those phases for surface materials on the plains and in the Columbia Hills of Gusev crater. Eight Fe‐bearing phases were identified: olivine, pyroxene, ilmenite, magnetite, nanophase ferric oxide (npOx), hematite, goethite, and a Fe3+‐sulfate. Adirondack basaltic rocks on the plains are nearly unaltered (Fe3+/FeT < 0.2) with Fe from olivine, pyroxene (Ol > Px), and minor npOx and magnetite. Columbia Hills basaltic rocks are nearly unaltered (Peace and Backstay), moderately altered (WoolyPatch, Wishstone, and Keystone), and pervasively altered (e.g., Clovis, Uchben, Watchtower, Keel, and Paros with Fe3+/FeT ∼ 0.6–0.9). Fe from pyroxene is greater than Fe from olivine (Ol sometimes absent), and Fe2+ from Ol + Px is 40–49% and 9–24% for moderately and pervasively altered materials, respectively. Ilmenite (Fe from Ilm ∼3–6%) is present in Backstay, Wishstone, Keystone, and related rocks along with magnetite (Fe from Mt ∼10–15%). Remaining Fe is present as npOx, hematite, and goethite in variable proportions. Clovis has the highest goethite content (Fe from Gt = 40%). Goethite (α‐FeOOH) is mineralogical evidence for aqueous processes because it has structural hydroxide and is formed under aqueous conditions. Relatively unaltered basaltic soils (Fe3+/FeT ∼ 0.3) occur throughout Gusev crater (∼60–80% Fe from Ol + Px, ∼10–30% from npOx, and ∼10% from Mt). PasoRobles soil in the Columbia Hills has a unique occurrence of high concentrations of Fe3+‐sulfate (∼65% of Fe). Magnetite is identified as a strongly magnetic phase in Martian soil and dust.

Juvenile chemical sediments and the long term persistence of water at the surface of Mars

“…Many of the same strata that contain opaline silica are thought to contain ferricopiapite, an Fesulfate mineral which forms at pH on the order of 1 or less (Milliken et al, 2008 (Morris et al, 2006). Schwertmannite, an iron oxyhydroxysulfate, rapidly decomposes to either jarosite or goethite over a range of pH and so its preservation on the martian surface could also indicate a water-limited history.…”

The evolution of a heterogeneous Martian mantle: Clues from K, P, Ti, Cr, and Ni variations in Gusev basalts and shergottite meteorites

“…Some SO 3 may have been added by alteration, but renormalization would change compositions by ∼ 1-3% with little effect on classifications or interpretations. Some amount of alteration has affected all the basaltic classes since amorphous nanophase ferric oxide (npOx) accounts for a portion of their Mössbauer spectra (4% in Irvine to up to 13% in Backstay; Morris et al, 2006;. The npOx alteration is likely a product of local low temperature alteration , possibly derived by the oxidation and devitrification of volcanic glass (Schmidt et al, 2009).…”

Thermal conductivity calculation in anisotropic crystals by molecular dynamics: Application to α−Fe2O3

“…As such, we focused in a first step on developing a methodology that we then applied to iron oxide (hematite) as a model material for the surface of the solid parts of the engine and we considered a temperature range between 300 and 500 K. In addition to its industrial and technological importance 18 , in recent years hematite has been subject to a renewed interest due to discoveries concerning the geological structure and mineral properties of Mars [19][20][21] . Bulk hematite (α-Fe 2 O 3 ), of space group R3c(167) , has a crystal structure that can be indexed as hexagonal with a unit cell consisting of 6 formula units in which the oxygen ions lie approximately in a hexagonal close-packed framework while the iron ions are positioned symetrically in two-thirds of the octahedral interstices 22,23 .…”