Jarosite – Indicator of (liquid) water on Mars

Jarosite

• Named after its type locality, Barranco del Jaroso in the Sierra Almagrera (near Los Lobos, Cuevas del Almanzora, Almería, Spain)
• In 2004 the Mars Exploration Rover – B found Jarosite on Mars. Because on Earth Jarosite is only formed in liquid water, this finding strongly indicates that Mars once possessed large amounts of liquid water.
• Formula: KFe₃(OH)₆(SO₄)₂
• Space group: R-3m (No. 166)
• Crystal system: trigonal
• Crystal class: -3m
• Lattice parameters: a = b = 7.304 Å, c = 17.268 Å, α = β = 90°, γ = 120°

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Picture: CC BY-SA 3.0 | Christian Rewitzer

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Crystal structure (click on the picture to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,” J. Appl. Crystallogr., 44, 1272-1276 (2011).)

• KO₁₂ only very slightly distorted icosahedra (purple)
• FeO₆ octahedra (blue)
• SO₄ tetrahedra (yellow)
• Oxygen (red)

For a 3D interactive version, see here:

https://skfb.ly/6pGuY

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