Comparative Climatology III 2018 (LPI Contrib. No. 2065) 2044.pdf

USING EXOPLANET CLIMATE SIMULATIONS AS A TOOL FOR CONSTRAINING ASTROECOLOGY MODELS. A.Y. Ceja1* and S. R. Kane1†, 1University of California, Riverside, Department of Earth Sciences, 900 University Ave., Riverside, CA, 92521, *[email protected], †[email protected].

Introduction: The field of astrobiology aims to Further, these analyses will identify types of organisms identify other habitable worlds. To date, thousands of viable to survive on a given exoplanet climate. Thus, we exoplanets with a diversity of properties have been can exploit the known metabolic byproducts to identify discovered, some of which are potentially habitable [1]. potential sources of observable biosignatures of the Exoplanet habitability is primarily determined by recommended exoplanet targets. surface climate conditions. The habitability of Earth, for References: [1] Petigura E. et al. (2013) PNAS, example, is chiefly a consequence of continually 110, 19273-19278. [2] Huey R.B. and Kingsolver J.G. (relatively) mild ambient temperatures [2,3,4]. Thus, on (1989) Trends Ecol. Evol., 4, 131-135. [3] Stillman first order, exoplanet habitability must be constrained J.H. and Somero G. (1996) JEB, 199, 1845-1855. [4] by surface temperature conditions. Miller L. et al. (2009) Fun. Eco., 23, 756-767. [5] Exoplanet temperature profiles are often explored Woodsworth R. et al. (2015) JGR, 120, 1201-1219. [6] with the use with the use of General Circulation Models Kaspi Y. and Showman A.P. (2015) ApJ, 804, 1-18. [7] (GCMs) [5]. GCMs take as inputs key orbital Way M.J. et al. (2017) ApJ, 231, 12-34. parameters to simulate the probable climate generated by a planet with such properties. Orbital eccentricity and obliquity regulate the received stellar radiative flux on a planet, thus these parameters drive surface temperature conditions [6] and habitability. For an Earth-like planet in the circumstellar habitable zone (CHZ) with variable eccentricity and obliquity, time- dependent surface temperatures may be significantly perturbed. In this research, a modeling approach is outlined for which simulated temperature profiles of Earth analogs on variable eccentric and oblique orbits serve as environmental inputs for a previously developed astroecology model. The simulations are run with the program Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments (ROCKE-3D) [7], a fully-coupled 3-dimensional GCM developed at the NASA Goddard Institute for Space Studies. Methods: ROCKE-3D is used to produce temperature profiles of Earth analogs on variable eccentric and oblique orbits. These thermal profiles serve as environmental inputs for a previously developed agent rule-based astroecology model. The astroecology model is used to determine thresholds in eccentricity and obliquity of eta-Earths based upon thermophysiological limits of terrestrial organisms. This model will be applied for confirmed CHZ exoplanets. Conclusions: The applied methodology will place eccentricity and obliquity limits for the habitability of Earth-like planets. CHZ exoplanets with these parameters will be recommended as high-priority targets for future missions (e.g. James Webb Space Telescope). Confirmed CHZ exoplanets found to be suitable for terrestrial organisms are termed habitable (concerning only temperature and liquid water).