Abstract

Mid-IR Spectral Search for Salt Signatures on Solar System Bodies

Tracy M. Becker (Southwest Research Institute)

Jennifer Hanley (Lowell Observatory), Lorenz Roth (Royal Institute of Technology (KTH)), Kurt D. Retherford (Southwest Research Institute), Thomas Greathouse (Southwest Research Institute), Constantine Tsang (Southwest Research Institute)

Chlorinated salts (chloride, chlorate and perchlorate) are expected to exist on planetary bodies throughout the Solar System, likely forming through the interaction of rocky, chondritic material and liquid water at some point in the objects’ history. The presence of these salts establishes a wider range of temperatures for which liquid water is stable. Chlorinated salts have been hypothesized to be present on the trailing hemisphere of the surface of Jupiter’s moon Europa, causing that hemisphere to be distinctively dark at near-IR wavelengths. The presence of these salts on the surface of Europa would indicate interaction between the surface and sub-surface liquid ocean, and would constrain the temperature of the liquid reservoir and the thickness of Europa’s ice shell.

Recent laboratory studies have revealed diagnostic spectral features of chlorinated salts at mid-IR wavelengths. However, few observations of Europa or any of the Gallilean satellites have been made at these wavelengths with sufficient resolving power to identify such features. We present a spectral comparison of laboratory data with mid-IR observations of Europa and Callisto obtained by the NASA IRTF/TEXES instrument between 10-11 microns with R~2,500, which leads us to a discussion of the opportunities to expand such studies using the MIRI instrument on the JWST with a similar R~3000. The improved ~0.28” spatial resolution provided by MIRI/MRS mode 1B would cover up to 16 pixels across Europa’s disk, enabling comparisons of hemispherical regions. Future JWST observations could be used to study a variety of solar system objects to detect chlorinated salts and to garner details about the past or current presence of a liquid reservoir on small bodies throughout the solar system.

Mode of presentation: poster