UV Transmission in Prebiotic Environments on Early Earth

Area of Science:

• Astrobiology
• Origin of Life Studies
• Photochemistry

Background:

• Ultraviolet (UV) radiation is a key factor in origin of life scenarios.
• UV light can drive prebiotic chemistry, but its transmission through early Earth waters is poorly constrained.
• Understanding UV light's role requires knowledge of its absorption by prebiotic molecules.

Purpose of the Study:

• To experimentally determine the UV absorption properties of molecules relevant to prebiotic synthesis.
• To provide data for modeling UV photon penetration in plausible early Earth aquatic environments.
• To refine constraints on the conditions and chemical pathways for the origin of life.

Main Methods:

• Measurement of molar decadic extinction coefficients for small prebiotic feedstock molecules.
• Experimental determination of UV absorption spectra.
• Comparison of absorption spectra of simple molecules with those of nucleobases (e.g., adenine).

Main Results:

• Many small prebiotic feedstock molecules exhibit maximal UV absorption at short wavelengths (~200 nm).
• UV absorption generally decreases with increasing wavelength for these molecules.
• The nucleobase adenine shows significantly higher UV absorption compared to simpler prebiotic molecules.

Conclusions:

• Measured extinction coefficients allow calculation of UV photon penetration depths in prebiotic water.
• Results help constrain the plausibility and self-consistency of origin of life scenarios.
• Improved understanding of the prebiotic UV environment aids in defining necessary chemical and environmental conditions for early life formation.