Statement

Gamma radiolysis of water produces reactive species (OH•, H₂O₂, H₂) with well-established G-values that can oxidize Fe²⁺ to Fe³⁺ in hydrous mineral phases.

Evidence

Spinks & Woods 1990, An Introduction to Radiation Chemistry (3rd ed.), Wiley-Interscience. ISBN 978-0-471-61403-6

Primary radiolysis products and G-values (molecules per 100 eV):

• G(OH•) ≈ 2.7 (hydroxyl radical)
• G(H₂O₂) ≈ 0.7 (hydrogen peroxide)
• G(H₂) ≈ 0.45 (molecular hydrogen)
• G(eaq⁻) ≈ 2.7 (solvated electron)

OH• and H₂O₂ are strong oxidizers capable of converting Fe²⁺ → Fe³⁺ in hydrous phases.

Argument

A1: Water radiolysis is well-characterized physics with established G-values. The production of OH•, H₂O₂, and other reactive species from water irradiation is among the most thoroughly studied radiation chemistry phenomena. G-values are reproducible across independent laboratories and decades of work.

A2: The effect is conditional on water presence. Radiolytic oxidation of Fe²⁺ requires liquid or adsorbed water as the source of oxidizing radicals. Anhydrous mineral phases lack this reaction medium.

Implication

Supports "Partially Affected" for techniques analyzing redox-sensitive species in potentially hydrous samples:

• MÖSSBAUER SPECTROSCOPY × SCI 1.3 (Post-lithification history)
• XANES × SCI 1.3
• TEM-EELS × SCI 1.3
• Redox state in hydrous phases may reflect post-sterilization chemistry rather than original Mars conditions.

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