We propose to conduct an interdisciplinary study of exoplanetary climates and chemistry affected by extreme X-ray and UV (XUV) radiation and high fluxes from energetic protons accelerated in CME-driven shocks from active stars. Using a hierarchy of models (PATH-Aeroplanet Chemistry-ROCKE3D), the team will simulate self-consistent 3D atmospheres with many gas species not explored previously. ROCKE3D simulations will provide transmission spectra from climatologically consistent terminator profiles and spectrally resolved phase curves.

A large number of stellar and planetary properties can influence whether a planet can be habitable. Current exoplanet surveys measure the size and/or mass of a planet, the orbital distance, and the host star's properties, which can tell us if a planet resides in an orbit that would allow it to sustain liquid water on its surface. This project will use dynamical models to further explore the habitability of exoplanets by simulating the accretion of oceans and atmospheres during their formation, processes that cannot be measured directly. These numerical models will help us understand what types of stellar environments (e.g., low mass stars, binary stars) allow the formation of water-rich Earths, and which would be capable of retaining their oceans and atmospheres during the giant impact phase of planet formation.

This project studies effects of ion molecular reactions on the photochemistry of current Mars, early Earth and exoplanets. Specific goals are to explore: the possibility of rapid atmospheric methane destruction by ion species produced by cosmic rays in the atmosphere of Mars; the effects of increased cosmic ray exposure of the atmospheres and ancient habitability of early Earth and Mars; and the applications of ion chemistry in the atmospheres of terrestrial-like exoplanets.

This project involves modification of existing interior structure and thermal evolution models to calculate surface conditions for planets with thin gaseous envelopes for both hydrogen/helium and water dominated atmospheres. With these modifications, the PI will run a large suite of thermal evolution models for both solar composition and water-dominated atmospheres across a wide range of planetary masses, volatile envelope fractions, irradiations, and ages in order to determine the location and shape of the boundary at which volatile envelopes become too large to support liquid water on their surfaces.

This project will use Atmos, a publicly available 1-D coupled photochemical/climate model, to synthesize atmospheres of different classes of exoplanets (from terrestrial to gas giants). Understanding and modeling the diversity of possible planetary environments is important for anticipating the needs of future NASA observatories. In particular, environments that are photochemically self-consistent with the host star properties and climatically self-consistent with the planetary orbital distance will allow us to predict the types of worlds (including habitable worlds) that may exist elsewhere in the universe. This project will also involve upgrades to the Atmos model as a community tool.

This project will use the Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE3D) general circulation model (GCM) to perform simulations that examine the variability in planetary climates detectable by a future Large Ultraviolet, Optical, and Infrared (LUVOIR) space telescope. Specifically, this project will address two aspects of planetary habitability: the role of continental and ocean configuration and planetary rotation rate.

This project continues earlier work on using GEOS-CCM calculations to study the effects that orbital eccentricity has on a planet’s climate and habitability. We examine a Earth-like planet with orbital eccentricities of 0.017, 0.06, and 0.25, in order to determine the effects of eccentricity on climate and atmospheric composition. The GEOS-5 General Circulation Model has a dynamic ocean, (Modular Ocean Model), dynamic sea ice (CICE module), and realistic stratospheric chemistry (StratChem module).

This project will use state-of-the-art 3-D climate models (the CAM, ROCKE3D and LMDG models) to simulate spectrally resolved thermal phase curves in each of the nine JWST/MIRI photometric filters, and generate longitudinal brightness maps we would expect to get with JWST from simulated terrestrial planets in and near the habitable zone (HZ) of low-mass stars. Model inter-comparison like that used in this project is imperative to ensure consistent results, and is already widely used to evaluate anthropogenic climate change. This project will also generate disk-averaged reflected light and transit transmission spectra using SMART (Spectral Mapping Atmospheric Radiative Transfer Model), a versatile line-by-line fully multiple scattering 1-D radiative transfer model.

This study involves modeling the conditions for the habitability of magnetized terrestrial type exoplanets. The global conditions of exoplanetary habitability will be determined based on: 1) how efficiently a global exoplanetary dipole magnetic field can be generated via dynamo action in the molten planetary cores; 2) on the minimum exoplanetary magnetic dipole moment needed to shield against the dynamic pressure and magnetic field produced by the magnetic activity of the planet-hosting stars. The results of this research will provide fundamental global conditions for identifying habitable exoplanets based on planetary mass and chemical composition; the magnetic activity of their parent stars; and the benchmarking parameters for geodetic measurements in future exoplanetary missions.

The team will calculate photo-evaporative escape rates using the open source ionization and radiative transfer code CLOUDY (Ferland et al. 2017). Model development and validation will be carried out to assess the impact of cooling due to metals and molecular coolants in planetary atmospheres. These models will be used to compute photo-evaporative escape rates over a wide range of planet masses, radii, atmospheric metallicities, irradiations, and host stellar types. The models will be precomputed on a grid of planetary and stellar properties, which will then be made publicly available to the community through EMAC. Additionally, the team will make predictions for the detectability of exospheric metal species with FUV transmission spectroscopy.

This project will first use models of stellar extreme ultraviolet (XUV)-driven atmospheric loss for energy-limited and recombination-limited escape to predict how heating and escape rates vary as function of planet mass, radius, irradiation, and stellar type. Second, the project will combine a magnetohydrodynamic magnetospheric model and a polar wind model to calculate atmospheric Joule heating rates and ion escape due to XUV and stellar wind. These heating and escape rates will be compared to determine the relative impact of these mechanisms on enhancing atmospheric escape at the evolutionary timescale.

The goal of this work is to understand how the distribution of surface life over a planet is sensitive to the distribution of available water and feedbacks between that life and the planet’s climate. Understanding these distributions will constrain the activity of a planet’s biosphere and hence the likely detectability of gaseous and surface biosignatures. Using the NASA Goddard Institute for Space Studies (GISS) Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) GCM, this investigation starts with idealized all-land abiotic planets, then couples in a surface life form, to lay foundations for eventually understanding the spatial distribution of surface habitability (liquid water availability) and biota on rocky exoplanets with more complex surfaces and land/ocean configurations. The surface “life form” will “seek the water” in the model, altering the planetary albedo and water conductance and feeding back into climate.

Understanding exoplanetary habitability requires knowledge of how atmospheres evolve and respond to the penetration of extreme ultraviolet and energetic particle fluxes. The interaction of these fluxes with constituent molecules affect the chemistry and the atmospheric loss of neutral and ion species. The focus of this project is on the physical mechanisms involved in atmospheric dynamics driven by space weather events and resulting atmospheric escape that may cause substantial erosion of exoplanetary atmospheres and changes in atmospheric chemistry with potential effects on habitability.