Identifiable Acetylene Features Predicted for Young Earth-like Exoplanets with Reducing Atmospheres Undergoing Heavy Bombardment

Identifiable Acetylene Features Predicted for Young Earth-like Exoplanets with Reducing Atmospheres Undergoing Heavy Bombardment

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...

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Bibliographic Details
Published in:The Astrophysical journal Vol. 888; no. 1; pp. 21 - 32
Main Authors: Rimmer, P. B., Ferus, M., Waldmann, I. P., Kní ek, A., Kalvaitis, D., Ivanek, O., Kubelík, P., Yurchenko, S. N., Burian, T., Dostál, J., Juha, L., Dud ák, R., Krůs, M., Tennyson, J., Civiš, S., Archibald, A. T., Granville-Willett, A.
Format: Journal Article
Language:English
Published: Philadelphia The American Astronomical Society 01-01-2020
IOP Publishing
Subjects:
Acetylene
Airglow
Ammonia
Astrochemistry
Astrophysics
Atmospheric models
Bombardment
Boundary conditions
Carbon monoxide
Computer simulation
Cyanoacetylene
Earth surface
Energy sources
Exoplanet atmospheres
Extrasolar planets
Extrasolar rocky planets
High power lasers
Hydrogen
Hydrogen cyanide
Impact phenomena
Laboratory astrophysics
Mixing ratio
Molecular spectroscopy
Organic chemistry
Planetary atmospheres
Plasma physics
Protoplanetary disks
Reducing atmospheres
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Summary: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 m.
Bibliography:AAS17383
The Solar System, Exoplanets, and Astrobiology
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ab55e8