Light Scattering Measurements of KCl Particles as an Exoplanet Cloud Analog
arXiv:2411.00952 · doi:10.3847/PSJ/ad6569
Abstract
Salt clouds are predicted to be common on warm exoplanets, but their optical properties are uncertain. The Exoplanet Cloud Ensemble Scattering System (ExCESS), a new apparatus to measure the scattering intensity and degree of linear polarization (DOLP) for an ensemble of particles, is introduced here and used to study the light scattering properties of KCl cloud analogs. ExCESS illuminates particles with a polarized laser beam (532 nm) and uses a photomultiplier tube detector to sweep the plane of illumination. Scattering measurements for KCl particles were collected for three size distributions representative of modeled clouds for the warm exoplanet GJ 1214b. Our measurements show that Lorenz-Mie calculations, commonly used to estimate the light scattering properties of assumedly spherical cloud particles, offer an inaccurate depiction of cubic and cuboid shaped KCl particles. All of our measurements indicate that Lorenz-Mie scattering overestimates the backscattering intensity of our cloud analogs and incorrectly predicts the scattering at mid-phase angles (~90 degrees) and preferential polarization state of KCl scattered light. Our results align with the general scattering properties of non-spherical particles and underscore the importance of further understanding the effects that such particles will have on radiative transfer models of exoplanet atmospheres and reflected light observations of exoplanets by the upcoming Nancy Grace Roman Space Telescope and Habitable Worlds Observatory.
Published in the Planetary Science Journal
References in corpus (13)
- HAT-P-26b: A Neptune-Mass Exoplanet with a Well Constrained Heavy Element Abundance
- Spectropolarimetric signatures of Earth-like extrasolar planets
- A reflective, metal-rich atmosphere for GJ 1214b from its JWST phase curve
- Spitzer Transits of the Super-Earth GJ1214b and Implications for Its Atmosphere
- VLT/FORS2 comparative transmission spectroscopy II: confirmation of a cloud-deck and Rayleigh scattering in WASP-31b, but no potassium?
- The Nancy Grace Roman Space Telescope Coronagraph Instrument (CGI) Technology Demonstration
- Experimental phase function and degree of linear polarization of cometary dust analogs
- A Universal Cloud Composition on the Nightsides of Hot Jupiters
- Retrieving Dust Grain Sizes from Photopolarimetry: An Experimental Approach
- The Impact of Phase Equilibrium Cloud Models on GCM Simulations of GJ~1214b
- A comparative study of WASP-67b and HAT-P-38b from WFC3 data
- Colors of an Earth-like exoplanet -- Temporal flux and polarization signals of the Earth
- Polarized Signatures of a Habitable World: Comparing Models of an Exoplanet Earth with Visible and Near-infrared Earthshine Spectra