LABORATORY STUDIES OF CRYOGENIC OUTER SOLAR SYSTEM MATERIALS

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.

For targets in the outer Solar System, the Ices Lab of the Astrophysical Materials Laboratory 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.

Some exciting results include applications to New Horizon’s infrared observations of Pluto, understanding the seas of Titan, and studying the surface of Europa. The ices that can be created in the lab are useful to a variety of outer solar system bodies.

We would like to be able to study not only the spectroscopic properties of these materials at low temperatures, but the physical properties as well. These include density, viscosity, sound speed, vapor pressure, refractive index, compressibility, thermal and electrical conductivity, and diffusion rates. Our group includes expertise in physical chemistry, specifically using theoretical and computational chemistry to understand the behavior of complex condensed phase systems. We are eager to collaborate with other complementary facilities, as well as scientists who have a need for laboratory data to help with understanding mission and/or telescope data.