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Characterization of Hazy Planetary Atmospheres

Presentation #627.05 in the session Planetary Atmospheres - Theory.

Published onApr 03, 2024
Characterization of Hazy Planetary Atmospheres

The Habitable Worlds Observatory (HWO) is an under-development NASA space telescope mission concept that will observe exoplanets by direct imaging to study their atmospheres. Exoplanets that have been observed thus far, mainly with transit spectroscopy, have shown a ubiquitous presence of hazes in clouds in their atmospheres. Characterization of these atmospheres relies on modeling for interpretation of the observed spectra. However, current atmospheric models for exoplanets generally adopt untested, low-complexity treatments for hazes and clouds, thus limiting the analysis of the data. In order to prepare an accurate model ahead of the HWO data collection, we must turn to analog environments in order to test and fit our haze parameterizations. Objects within our Solar System make for excellent candidates to develop this model since they are ground-truthed, thus enabling identification of biases that occur when aerosols are treated in a simplified manner. Within our Solar System, Titan is likely the best analog to hazy exoplanets. The Cassini-Huygens mission and numerous ground-based telescope campaigns provide essential ground truth observations of Titan, allowing us to check model retrievals against measured values to ensure accuracy. We developed a haze parameterization model with wavelength-dependent expressions for absorption and scattering efficiencies, as well as single-scattering albedo. We apply our atmospheric retrieval model to visible-wavelength observations of Titan’s geometric albedo from Karkoschka (1998). Preliminary results demonstrate a significant improvement from past models that do not incorporate the wavelength-dependence of atmospheric haze. We are also in the process of fitting the model to our own spectra from the Lowell Discovery Telescope’s EXtreme PREcision Spectrometer (EXPRES) and Near-Infrared High-Throughput Spectrometer (NIHTS) to monitor Titan’s haze and methane abundances (see Hanley et al, this conference, for more information on the observations).

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