Statement

Crystalline mineral structures (detectable by XRD, EBSD) are preserved at gamma doses up to >1 MGy; amorphization requires significantly higher doses and is rapidly annealed at room temperature.

Evidence

Plötze et al. 2003, Applied Clay Science 23(1–4):195–202. DOI: 10.1016/S0169-1317(03)00103-0

• Clay mineral studies demonstrate structural stability under gamma irradiation
• Ionization damage anneals at room temperature

Velbel et al. 2022, Astrobiology 22(S1):S112–S164. DOI: 10.1089/ast.2021.0113

• SS-1 classification: XRD and related techniques classified as "sterilization-tolerant"

Argument

A1: The physical mechanism precludes damage at this dose. 662 keV gamma photons produce ionization (electron displacement), not atomic displacement. Ionization damage in crystalline minerals creates transient defect centers that anneal spontaneously at room temperature. Amorphization requires sustained atomic displacement, which demands doses exceeding 1 MGy.

A2: Independent confirmation from MSR Science Team. Velbel et al. (2022) independently classified XRD and related crystallographic techniques as SS-1 (sterilization-tolerant).

Implication

Supports "not affected" for all crystallographic techniques:

• XRD × all columns
• SYNCHROTRON XRD × all columns
• EBSD × all columns

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