Persistence of flare-driven atmospheric chemistry on rocky habitable zone worlds

Howard Chen*, Zhuchang Zhan, Allison Youngblood, Eric T. Wolf, Adina D. Feinstein, Daniel E. Horton

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

75 Scopus citations

Abstract

Low-mass stars show evidence of vigorous magnetic activity in the form of large flares and coronal mass ejections. Such space weather events may have important ramifications for the habitability and observational fingerprints of exoplanetary atmospheres. Here, using a suite of three-dimensional coupled chemistry–climate model simulations, we explore effects of time-dependent stellar activity on rocky planet atmospheres orbiting G, K and M dwarf stars. We employ observed data from the MUSCLES campaign and the Transiting Exoplanet Survey Satellite and test a range of rotation period, magnetic field strength and flare frequency assumptions. We find that recurring flares drive the atmospheres of planets around K and M dwarfs into chemical equilibria that substantially deviate from their pre-flare regimes, whereas the atmospheres of G dwarf planets quickly return to their baseline states. Interestingly, simulated O2-poor and O2-rich atmospheres experiencing flares produce similar mesospheric nitric oxide abundances, suggesting that stellar flares can highlight otherwise undetectable chemical species. Applying a radiative transfer model to our chemistry–climate model results, we find that flare-driven transmission features of bio-indicating chemical species, such as nitrogen dioxide, nitrous oxide and nitric acid, show particular promise for detection by future instruments.

Original languageEnglish (US)
Pages (from-to)298-310
Number of pages13
JournalNature Astronomy
Volume5
Issue number3
DOIs
StatePublished - Mar 2021

Funding

H.C. and D.E.H. acknowledge support from the Future Investigators in NASA Earth and Space Science and Technology (FINESST) Graduate Research Award Number 80NSSC19K1523. H.C. thanks P. Loyd for assistance in the use of his MUSCLES flare code and for sharing it with the public. Z.Z. acknowledges support from the MIT BOSE Fellow programme, the Change Happens Foundation and the Heising-Simons Foundation. E.T.W. acknowledges support from NASA Habitable Worlds grant number 80NSSC17K0257. A.D.F. acknowledges support from NSF Graduate Research Fellowship Program grant number DGE-1746045. We thank A. Gu for ozone variability analysis inspiration and the QUEST high-performance computing facility at Northwestern University for computational and staff resources. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the funding agencies. This paper includes data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program. TESS data were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract number NAS5-26555. Support for MAST is provided by the NASA Office of Space Science via grant number NNX13AC07G and by other grants and contracts.

ASJC Scopus subject areas

  • Astronomy and Astrophysics

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