OSL DATING PROPERTIES OF MG-CARBONATE: A RECENTLY DISCOVERED MINERAL IN MARTIAN SEDIMENTS

Optically stimulated luminescence (OSL) has been proposed for remote, in-situ age-dating on Mars. The strength of OSL as a dating method lies in its ability to determine absolute depositional ages for sediments and landforms. With the discovery of magnesite, a naturally occurring Mg-carbonate mineral and a long anticipated marker of an aqueous past on Mars, it has become important to understand the OSL properties of the mineral in order to ascertain its influence on in-situ optical dating of silicates and/or its viability as a geochronometer. Natural and synthetic MgCO3 samples were obtained and characterized using powder XRD. The natural sample was predominantly magnesite with a minor component of dolomite, while the synthetic sample was magnesium carbonate monohydrate. Basic optical dating properties of radiation dose response, measurement-induced sensitivity change, and short-term signal fading were evaluated for the magnesium carbonate samples using both blue and infrared stimulation and monitoring of the subsequent luminescence in the UV range. No thermal pretreatments were employed. Our OSL characterizations for these materials are generally consistent with other dosimetric materials, particularly geologic salts. However, the response of the natural sample stimulated in the infrared and monitored in the UV was distinctly different from the remainder of the set. The results of our investigation will be presented and the implications for in-situ optical dating on Mars will be discussed.