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Project Progress

This task uses sophisticated spatially and spectrally-resolved radiative transfer models and data from planets in our own Solar System to explore the detectability of surface and atmospheric properties of terrestrial planets from disk-averaged spectra at a number of different spectral resolutions. These models, which simulate both surface and atmospheric properties for a variety of viewing angles, illuminations, surface type, and cloud coverage, provide tools to better understand the likely sensitivity of planet detection and characterization missions such as TPF/Darwin to both local and global planetary properties.

This year, we completed the Mars and Earth models, and validated the resultant disk-averaged spectra against observations acquired by approaching or orbiting spacecraft, and Earthshine measurements from ground-based observations of the Moon. The validated planetary models, and TPF instrument simulator models were used to explore the detectability of features for Mars-like (likely abiotic) and Earth-like (life-supporting) planets. The resultant products include: 1) globally averaged synthetic spectra from 0.1 to 160 µm for both planets, 2) light-curves and the spectral variability at visible and infrared (IR) wavelengths as a function of viewing angle and season, and 3) simulations of an increasingly frozen Mars, and an increasingly cloudy/forested/oceanic Earth.

From the Mars modeling, we found that although disk-averaging clearly reduced the influence of localized features, we were able to detect differences in the observed spectra as a function of season at all wavelengths, as either changes in observed intensity or spectral shape. These seasonal variations were related either to changes in atmospheric density, surface temperature, or aerial coverage of surface ice, and were most pronounced for the millimeter imaging radiometer (MIR) spectra. Our Mars results have been submitted for publication, and our Earth results are currently being prepared for publication. Ongoing work on this project in the coming year will also include similar models for Venus and Titan.

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