SPECTRAL, GEOCHEMICAL, AND GEOPHYSICAL LABORATORY STUDIES RELEVANT TO PLANETARY GEOLOGY (Invited Presentation)

A variety of laboratory techniques can be adapted to planetary geology, but the main challenge is reproducing the relevant processes and conditions applicable to the planetary body. Thus, laboratory experiments work in tandem with in situ and remote sensing observations, as well as modeling, to explore and understand other planetary bodies.

Laboratory experiments were key to understanding flows on Mars, e.g. Recurring Slope Lineae (RSL). Laboratory measurements of the spectral properties of hydrated chlorine salts allowed detection of these species within the RSL, indicating that brines contribute to the flow. Further experiments regarding the stability of those brines under Martian conditions help explain the longevity and characteristics of those flow features. It was especially important to measure the spectral, geochemical and geophysical properties at the appropriate temperature because the hydration state of salts is closely tied to both temperature and pressure, as are the evaporation and deliquescence/efflorescence rates. Even the spectral features themselves are temperature sensitive.

For targets in the outer Solar System, the Astrophysical Ices Lab at Northern Arizona University is dedicated to studying ices under controlled temperatures and pressures. Simple molecules like CH₄, H₂O, N₂, and CO are important geological materials in the cold, outer regions of the Solar System. Their mobility and distinct material properties enable geological activity and produce a spectacular variety of exotic landforms, even at extremely low temperatures. But frustratingly little is known of the basic mechanical and optical properties of these volatile ices, and especially of their mixtures. Our cryogenic lab setup allows us to explore ices down to 30 K through imaging, and transmission and Raman spectroscopy. One recent exciting result has shown that although methane and ethane have similar freezing points (~91 K), when mixed they can remain liquid down to 72 K. Further studies of the stability and spectral properties of ices may yield other insights into the geologic processes of icy bodies.