UV IRRADIATION OF CARBONACEOUS METEORITES MAY SYNTHESIZE SMALL ORGANIC ACIDS ON MARS

Abstract

Organics are required for life as we know it and are ubiquitous to primitive abiotic exogenous materials, including carbonaceous chondrites [1,2]. Since biotic and abiotic synthesis mechanisms differ, organics bear molecular structures, distributions, and isotopic signatures that can indicate biological vs astrochemical/geological origin, making organics high-priority targets in astrobiological exploration of Mars [1]. Deconvolving the origin of Martian carbon is complex: multiple sources are expected, including exogenous delivery [2], abiotic in situ production [3], and potentially life [1]. Post depositional alteration via ionizing cosmic radiation and UV can complicate the signal [4]. Photochemical reactions can destroy, transform, or synthesize organics; radiolysis rates vary by molecule, functional group, and mineral associations [5]. Meteoritic organics are well-understood on Earth [2], but their evolution on Mars has not been constrained: characterizing UV alteration of exogenous organics is key to deconvolving the abiotic background for Mars life detection, especially compared to cosmic radiation, which alters organics differently [4,5]. Toward this goal, we exposed powdered Aguas Zarcas (AZ) meteorite and SiO2 blanks to Mars-like UV under analog conditions in the Planetary Atmospheres Chamber (PAC) [6] for ~100 sols equivalent.