How does the clay mineral saponite affect the photodegradation of the biomarker L-histidine under simulated Martian UV conditions?

L-histidine is an amino acid that could be a potential biomarker for life on Mars. Clay minerals like saponite are known for their ability to adsorb and intercalate organic molecules, which might protect them from degradation. This study investigates how L-histidine interacts with saponite and how these interactions influence its stability under Martian UV radiation.

From: "Photodegradation of the biomarker L-histidine induced by edge sites of a clay mineral in the Martian harsh UV environment", Icarus, Volume 442, December 2025, 116757

The study found that L-histidine adsorbed onto saponite degrades faster under UV radiation compared to pure L-histidine. This suggests that saponite acts as a photocatalyst, accelerating the degradation of L-histidine, likely due to active surface edge sites of the clay mineral. The interactions between L-histidine and saponite at different pH levels (acidic and basic) also affect the degradation rates, with faster degradation observed at acidic pH. This indicates that the clay mineral's edge sites play a significant role in the photodegradation process, which could have implications for the preservation of organic molecules on Mars.