CONSTRAINING OUR UNDERSTANDING OF THE ACTIONS AND EFFECTS OF MARTIAN VOLATILES THROUGH THE STUDY OF RETURNED SAMPLES.

Abstract

Volatiles have clearly played a key role in the evolution of Mars’ atmosphere, hydrosphere and geosphere, with effects ranging from the geomorphological evidence for outflow channels and valley networks early in Mars’ history to formation of alteration products in rocks to the current seasonal changes in the polar caps. It is clear that the absolute and relative abundances of various volatiles have changed through time via volcanic degassing, atmospheric loss, and interactions with the crust. In addition to studying the current Martian atmosphere and ancient trapped gasses in Martian sedimentary, igneous and impact samples, there is considerable knowledge to be gained by examining the compositions of sedimentary rocks, regolith and secondary minerals that are especially sensitive to climatic influences such as obliquity-driven changes. For example, results from the Curiosity rover indicate that it is possible to obtain high resolution chemostratigraphic climate records from rhythmically bedded sedimentary rocks using in situ measurements [1]. Analysis of selected returned samples from such in situ records would be extremely important in confirming and fully understanding such records. In addition, there is growing capability of applying a variety of radiometric techniques to dating of the time of sedimentation and obtaining such dates from climate-sensitive sedimentary sequences would greatly help to tie down the timescales of past climate changes. This is a provisional report from the iMOST subteam on key samples needed to understand volatiles.