Identifiable Acetylene Features Predicted for Young Earth-like Exoplanets with Reducing Atmospheres Undergoing Heavy Bombardment
Year: 2019
Type: article
Abstract: The chemical environments of young planets are assumed to be largely influenced by the impacts of bodies lingering on unstable trajectories after the dissolution of the protoplanetary disk. We explore the chemical consequences of impacts within the context of reducing planetary atmospheres dominated by carbon monoxide, methane, and molecular nitrogen. A terawatt high-power laser was selected in order to simulate the airglow plasma and blast wave surrounding the impactor. The chemical results of these experiments are then applied to a theoretical atmospheric model. The impact simulation results in substantial volume mixing ratios within the reactor of 5% hydrogen cyanide (HCN), 8% acetylene (C2H2), 5% cyanoacetylene (HC3N), and 1% ammonia (NH3). These yields are combined with estimated impact rates for the early Earth to predict surface boundary conditions for an atmospheric model. We show that impacts might have served as sources of energy that would have led to steady-state surface quantities of 0.4% C2H2, 400 ppm HCN, and 40 ppm NH3. We provide simulated transit spectra for an Earth-like exoplanet with this reducing atmosphere during and shortly after eras of intense impacts. We predict that acetylene is as observable as other molecular features on exoplanets with reducing atmospheres that have recently gone through their own “heavy bombardments,” with prominent features at 3.05 and 10.5 μm.
Source: The Astrophysical Journal
Institutions: MRC Laboratory of Molecular Biology, University of Cambridge, Czech Academy of Sciences, Czech Academy of Sciences, Heyrovsky Institute, University College London, Charles University, FZU - Institute of Physics of the Czech Academy of Sciences, Czech Academy of Sciences, Institute of Plasma Physics, National Centre for Atmospheric Science
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Awards: G12500569, UCL Astrophysics Consolidated Grant 2018-2021, G176604203, G234180954, G2390681306, G291036901, G341201585, G3490171961, ARIEL SCIENCE ADVISORY TEAM UK ACTIVITIES, G354964355, G3622461675, G4131035492, Plasma and UV/XUV/X-Ray Reprocessing of planetary atmospheres: What can we expect on young exoplanets?, G4280972364, G4380863602, G4474684054, G4499894601, G4651546194, G5705513129, G5916014575, G6424899965, G7363506711, G7417508181, G7689605238, G7991405179, UCL Astrophysics Consolidated Grant 2015-2018, G98017120
OpenAlex ID: W2988582677