The MUSCLES Program: Stellar Drivers for Atmospheric Chemistry and Stability around M dwarfs
Friday 6 July, 12:30
High-energy stellar photons and particles regulate the atmospheric temperature structure and photochemistry on orbiting planets, influencing the long-term stability of planetary atmospheres and the production of potential “biomarker” gases. Rocky planets orbiting M dwarfs will likely be the first exoplanets directly probed for signs of life, however, relatively few observational and theoretical constraints exist on the high-energy irradiance from typical (i.e., weakly active) M dwarf exoplanet host stars. I will describe results from an ongoing panchromatic survey (Chandra/XMM/Hubble/ground) of M dwarf exoplanet hosts. The MUSCLES* program combines UV, X-ray, and optical observations, reconstructed Lyman-alpha and EUV (10-90 nm) radiation, and next-generation stellar atmosphere models to provide realistic inputs for modeling the stability and climate on potentially habitable planets around cool stars. I will present an overview of the project and focus on three main results – 1) the evolution of the high-energy spectral energy distribution as a star’s habitable zone moves inward from 1 to 0.1 AU, including implications for the possible abiotic production of the suggested biomarkers O2 and O3, 2) new estimates of the high-energy particle fluxes (from CMEs/SEPs) from these stars based on solar UV flare/particle flux measurements, and 3) characterization of the high-energy variability on active and inactive M dwarfs, with an emphasis on the potential for these impulsive events to drive large-scale atmospheric evolution.
* Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems