Aerosols are a ubiquitous feature of exoplanet atmospheres, sometimes obscuring the spectral determination of atmospheric gas composition. Aerosol composition is usually determined from models of…

This is a $150,000.00 grant awarded by the National Aeronautics and Space Administration (NASA) to Arizona State University (ASU) to measure surface energies for several exoplanetary condensates and incorporate the data into atmospheric aerosol models for hot Jupiter exoplanets. The research will support NASA's Exoplanet Research Program by improving the interpretation of exoplanet observations. ASU, a comprehensive public research university, will synthesize nanoparticles and micron-sized particles of compounds like zinc sulfide and enstatite, and use calorimetry to determine their surface energies. This new data will be incorporated into the Community Aerosol and Radiative Model for Atmospheres (CARMA) code to calculate particle size distributions and radiative transfer properties in hot Jupiter atmospheres. No set-aside designation was identified for this award.

Aerosols are a ubiquitous feature of exoplanet atmospheres, sometimes obscuring the spectral determination of atmospheric gas composition. Aerosol composition is usually determined from models of nucleation rate for condensable species in an atmospheric of a given composition. For hot jupiters, condensable species include various silicates, sulfides, and other high temperature condensates. For lower temperature objects, such as warm neptunes and super earths, photochemical production of aerosol particles is predicted.to be dominant. Because IT is not yet possible to definitively determine aerosol composition through astronomical observations, IT is important to model aerosol production as accurately as possible. A key factor in the determination of nucleation rate is the surface energy of the nucleating material. High surface energy materials, such as forsterite, will nucleate much more slowly compared to lower surface energy materials, such as sulfides. Here, we propose to measure surface energies for several important and likely exoplanet.condensates including ZNS, MNS, NA2S (sodium sulfide), enstatite, and spinel. Surface energies will be determined by synthesizing nanoparticles and micron-sized particles of the compound of interest, and then using calorimetric techniques to measure the excess enthalpy as a function of particle surface area. From these data, an accurate surface energy is determined for both hydrous and anhydrous phases. The synthesis and calorimetry will be carried out in the navrotsky laboratory at ASU. This new surface energy data, together with the existing surface energy data that has up to now been not utilized by the exoplanet community, will be included.in nucleation rate calculations for hot jupiters. Finally, we will use the community aerosol and radiative model for atmospheres (carma ) code to calculate particle size distribution and radiative transfer properties of nucleating aerosols for representative hot jupiter atmospheres. The proposed research supports the exoplanet research program (XRP) with respect to interpretation of observations of exoplanets, and, in particular, our research provides laboratory data of high relevance to a broad range of exoplanet atmospheres.