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Habitability of Rocky Exoplanets: Insight from Laboratory Simulations
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  • Chao He,
  • Sarah Horst,
  • Nikole Lewis,
  • Julianne Moses
Chao He
Johns Hopkins University

Corresponding Author:che13@jhu.edu

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Sarah Horst
Johns Hopkins University
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Nikole Lewis
Cornell University
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Julianne Moses
Space Science Institute
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Thousands of exoplanets have been discovered in last two decades, including a sample of rocky worlds in the habitable zones of their host stars. Assessing their habitability will rely on the observation and characterization of atmospheres of these distant worlds. Laboratory simulations can provide critical information for atmospheric observations of exoplanets. Thus, we conducted a series of laboratory experiments that simulated a broad range of atmospheres in cooler (<800 K), smaller (<0.3× Jupiter’s mass) exoplanets. We investigated three types of atmospheric metallicities, 100× solar (H2-dominated), 1,000× (H2O-dominated), and 10,000× (CO2-dominated) at three temperatures, 300, 400, and 600 K using the PHAZER (Planetary Haze Research) chamber at Johns Hopkins University (He et al. 2017) with one of two energy sources (AC glow plasma and UV photons). We find that all simulated atmospheres resulted in haze formation with both energy sources, but the production rates vary a lot with different conditions (He et al. 2018a, 2018b; Hörst et al. 2018). The resulting haze particles can affect the atmospheric and surface temperature of the exoplanets, and their potential habitability. We monitored the gas phase compositional changes with a quadrupole mass spectrometry during the experiments and characterized the resulted haze particles. We find that the organic molecules are produced in both gas and solid phases, which could provide a source of organic material to the surface for life to arise. We identified potential precursors (C2H2, HCN, CH2NH, HCHO, etc.) for haze formation, among which HCHO and HCN are also important prebiotic precursors for products of biological significance (sugars, amino acids, and nucleobases). The laboratory results increase our understanding the habitability of exoplanets and can help guide and interpret current and future atmospheric observations of exoplanets. Ref: He, C., Hörst, S. M., et al. 2017, APJL, 841, L31 He, C., Hörst, S. M., Lewis, N. K., et al. 2018, ApJL, 856, L3 He, C., Hörst, S. M., Lewis, N. K., et al. 2018, AJ, 156, 38 Hörst, S. M., He, C., Lewis, N. K., et al. 2018, Nat. Astron., 2, 303