Statement

Radiation drives organic molecules toward macromolecular structures, causing loss of diagnostic molecular features and spectral convergence. Different organic sources become spectrally similar after irradiation.

Evidence

Fox et al. 2023, JGR Planets 128:e2022JE007624. DOI: 10.1029/2022JE007624

Radiation-induced transformation pathway:

1. Fresh biomolecules → Distinct molecular Raman/fluorescence signatures
2. Radiolysis → Bond breakage, radical formation
3. Recombination → Cross-linking, polymerization
4. Macromolecular carbon → Convergent D/G band signatures

Key observations:

• Fluorescence peaks shift and converge (295 nm → ~280 nm)
• Molecular Raman features progressively lost
• Different organics converge to similar G/D band ratios
• Kerogen-like structures more resistant (already macromolecular)

Argument

A1: Convergence is a radiation-driven endpoint, not a threshold effect. Radiation drives all organic molecules toward the same macromolecular carbon endpoint via bond scission → radical formation → cross-linking → polymerization. Different starting materials converge because they are all moving toward the same stable structure.

A2: Convergence specifically destroys discriminant information. The scientific value at stake is not "can we detect organics?" (the Aliphatic C-H Raman Band Preservation claim shows we can) but "can we tell where the organics came from?" Spectral convergence eliminates the molecular fingerprints needed for source attribution.

Implication

Supports "affected" for techniques requiring bio/abiotic molecular discrimination:

• Discriminant techniques cannot distinguish organic sources post-irradiation
• Even if organics survive, their diagnostic origin information is degraded
• Spectral convergence undermines SSA 1.2 (Abiotic Baseline) objectives

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