title: Exoplanetary Atmospheres-Chemistry, Formation Conditions, and Habitability.
abstract: Characterizing the atmospheres of extrasolar planets is the new frontier in exoplanetary science. The last two decades of exoplanet discoveries have revealed that exoplanets are very common and extremely diverse in their orbital and bulk properties. We now enter a new era as we begin to investigate the chemical diversity of exoplanets, their atmospheric and interior processes, and their formation conditions. Recent developments in the field have led to unprecedented advancements in our understanding of atmospheric chemistry of exoplanets and the implications for their formation conditions. We review these developments in the present work. We review in detail the theory of atmospheric chemistry in all classes of exoplanets discovered to date, from highly irradiated gas giants, ice giants, and super-Earths, to directly imaged giant planets at large orbital separations. We then review the observational detections of chemical species in exoplanetary atmospheres of these various types using different methods, including transit spectroscopy, Doppler spectroscopy, and direct imaging. In addition to chemical detections, we discuss the advances in determining chemical abundances in these atmospheres and how such abundances are being used to constrain exoplanetary formation conditions and migration mechanisms. Finally, we review recent theoretical work on the atmospheres of habitable exoplanets, followed by a discussion of future outlook of the field.
authors.affiliation: Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK.
authors.forename: Nikku
authors.initials: N
authors.lastname: Madhusudhan
authors.affiliation: Instituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain, marcelino.agundez@icmm.csic.es.
authors.forename: Marcelino
authors.initials: M
authors.lastname: Agúndez
authors.affiliation: Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA, jmoses@SpaceScience.org.
authors.forename: Julianne I
authors.initials: JI
authors.lastname: Moses
authors.affiliation: Laboratory for Climate and Ocean-Atmosphere Sciences, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China, yyhu@pku.edu.cn.
authors.forename: Yongyun
authors.initials: Y
authors.lastname: Hu
keywords: Atmospheric chemistry; Exoplanetary atmospheres; Exoplanets; Habitability; Planet formation