New Insights into Cosmic Ray induced Biosignature Chemistry in Earth-like Atmospheres

Abstract

With the recent discoveries of terrestrial planets around active M-dwarfs, destruction processes masking the possible presence of life are receiving increased attention in the exoplanet community. We investigate potential biosignatures of planets having Earth-like (N${}_2$-O${}_2$) atmospheres orbiting in the habitable zone of the M-dwarf star AD Leo. These are bombarded by high energetic particles which can create showers of secondary particles at the surface. We apply our cloud-free 1D climate-chemistry model to study the influence of key particle shower parameters and chemical efficiencies of NOx and HOx production from cosmic rays. We determine the effect of stellar radiation and cosmic rays upon atmospheric composition, temperature, and spectral appearance. Despite strong stratospheric O${}_3$ destruction by cosmic rays, smog O${}_3$ can significantly build up in the lower atmosphere of our modeled planet around AD Leo related to low stellar UVB. N${}_2$O abundances decrease with increasing flaring energies but a sink reaction for N${}_2$O with excited oxygen becomes weaker, stabilizing its abundance. CH${}_4$ is removed mainly by Cl in the upper atmosphere for strong flaring cases and not via hydroxyl as is otherwise usually the case. Cosmic rays weaken the role of CH${}_4$ in heating the middle atmosphere so that H${}_2$O absorption becomes more important. We additionally underline the importance of HNO${}_3$ as a possible marker for strong stellar particle showers. In a nutshell, uncertainty in NOx and HOx production from cosmic rays significantly influences biosignature abundances and spectral appearance.

Manuscript version after addressing all referee comments. Published in ApJ

References in corpus (10)

• The James Webb Space Telescope
• Extreme Water Loss and Abiotic O${}_2$ Buildup On Planets Throughout the Habitable Zones of M Dwarfs
• Strong Dependence of the Inner Edge of the Habitable Zone on Planetary Rotation Rate
• The Habitable Zones of Pre-Main-Sequence Stars
• UV Surface Environment of Earth-like Planets Orbiting FGKM Stars Through Geological Evolution
• Superflare occurrence and energies on G-, K- and M-type dwarfs
• NIR-Driven Moist Upper Atmospheres of Synchronously Rotating Temperate Terrestrial Exoplanets
• On the protection of extrasolar Earth-like planets around K/M stars against galactic cosmic rays
• 3D climate modeling of Earth-like extrasolar planets orbiting different types of host stars
• Transmission Spectroscopy with the ACE-FTS Infrared Spectral Atlas of Earth: A Model Validation and Feasibility Study

Cited by in corpus (23)

• Impact of low-energy cosmic rays on star formation
• Detectability of atmospheric features of Earth-like planets in the habitable zone around M dwarfs
• Persistence of Flare-Driven Atmospheric Chemistry on Rocky Habitable Zone Worlds
• Time-resolved spectroscopy and photometry of an M dwarf flare star YZ Canis Minoris with OISTER and TESS: Blue asymmetry in H$\alpha$ line during the non-white light flare
• From cold to hot irradiated gaseous exoplanets: Fingerprints of chemical disequilibrium in atmospheric spectra
• Distinguishing between wet and dry atmospheres of TRAPPIST-1 e and f
• APO & SMARTS flare star campaign observations I. Blue wing asymmetries in chromospheric lines during mid M dwarf flares from simultaneous spectroscopic and photometric observation data
• Consistently Simulating a Wide Range of Atmospheric Scenarios for K2-18b with a Flexible Radiative Transfer Module
• On the Diversity of M-Star Astrospheres and the Role of Galactic Cosmic Rays Within
• A New Model Suite to Determine the Influence of Cosmic Rays on (Exo)planetary Atmospheric Biosignatures -- Validation based on Modern Earth
• Proxima Centauri b: A Strong Case for including Cosmic-Ray-induced Chemistry in Atmospheric Biosignature Studies
• Possible Atmospheric Diversity of Low Mass Exoplanets, some Central Aspects
• Detectability of biosignatures on LHS 1140 b
• Stellar Proton Event-induced surface radiation dose as a constraint on the habitability of terrestrial exoplanets
• Triggered superradiance and fast radio bursts
• The Earth-like Galactic cosmic ray intensity in the habitable zone of the M dwarf GJ 436
• Alternative Methylated Biosignatures I: Methyl Bromide, A Capstone Biosignature
• Stratospheric dayside-to-nightside circulation drives the 3-D ozone distribution on synchronously rotating rocky exoplanets
• Atmospheric processes affecting methane on Mars
• Atmospheric Characterization via Broadband Color Filters on the PLAnetary Transits and Oscillations of stars (PLATO) Mission
• Modeling the astrosphere of LHS~1140
• Influence of Biomass Emissions upon Habitability, Biosignatures and Detectability in Earth-like Atmospheres
• SVEEEETIES: Singular vector expansion to estimate Earth-like exoplanet temperatures from infrared emission spectra