OPTICAL DATING PROPERTIES OF KIESERITE: AN IMPORTANT ACCESSORY MINERAL IN MARTIAN SEDIMENTS

Kieserite is a mono-hydrated magnesium sulfate salt that is believed to occur in abundance at the OPPORTUNITY rover landing site and is also thought to contribute to the elevated sulfur concentrations in sediments at other martian exploration sites. Optical dating is a terrestrial Quaternary geochronology method that has been proposed for in-situ robotic deployment on Mars. Optical dating, or OSL, is uniquely suited to provide sedimentary depositional ages that will be the key to unlocking and interpreting Mars' paleoclimatic and geomorphic history. Studies of analog materials are critical to establishing a firm foundation from which to launch optical dating for eventual application on Mars. The primary minerals that are used for optical dating are feldspars and quartz, whose optical dating properties have been studied and documented in the literature for decades. However, it is also important to understand how accessory minerals in the Martian sedimentary environment will affect optical dating efforts, as in-situ mineralogical separations will likely be limited or impractical. In this project we have evaluated the radiation dose response and the signal stability, two fundamental optical dating properties, of Kieserite and Magnesium hexahydrate. Our results suggest that the signal properties of hydrated magnesium sulfates share similarities with terrestrial feldspars and to some degree quartz. If these sulfate minerals occur in significant abundance within any particular sediment sample, they could contribute to the overall optical dating signal measured. Additional research with Kieserite and other naturally occurring salts anticipated to occur on Mars could elucidate ways in which their OSL signal contributions could be capitalized upon.