Ultra-short-period exoplanets such as 55 Cancri e (55 Cnc e), hosting dayside magma oceans, present unique opportunities to study surface-atmosphere interactions. The composition of a vaporized mineral atmosphere enveloping the dayside is dictated by that of the surface magma ocean, which in turn is sensitive to its oxygen fugacity (fO2). Observability estimations and characterization of the atmospheric emission of 55 Cnc e have mostly remained limited to low spectral resolution space-based studies. Here, we aim to examine ground-based high-resolution observabilities of a diverse set of mineral atmospheres produced across a grid of mantle fO2s varying over 12 orders of magnitude. We assume a bulk silicate Earth mantle composition and a substellar dayside temperature of T = 2500 K in the near-infrared wavelength region. This spectral range is often featureless for this class of atmospheres at low resolution. Coupling our newly developed simulator for synthesizing realistic observations from high-resolution ground-based spectrographs (Ratri) to a pre-developed high-resolution cross-correlation spectroscopy (HRCCS) analysis pipeline (Upamana), we find that this array of mineral atmospheres would all be detectable with 11 h of observing time of the dayside of 55 Cnc e with CARMENES and each individual scenario can be correctly differentiated within 1σ. Our analysis is readily able to distinguish between a planet with an Earth-like redox state (with f O2 ∼ 3.5 log10 units above the iron-wustite, ¨ IW buffer) and a Mercury-like planet (fO2 ∼ 5 log10 units below IW). We thus conclude that the HRCCS technique holds promise for cataloguing the diversity of redox states among the rocky exoplanetary population.
Detectability of oxygen fugacity regimes in the magma ocean world 55 Cancri e at high spectral resolution
Brogi, Matteo;
2025-01-01
Abstract
Ultra-short-period exoplanets such as 55 Cancri e (55 Cnc e), hosting dayside magma oceans, present unique opportunities to study surface-atmosphere interactions. The composition of a vaporized mineral atmosphere enveloping the dayside is dictated by that of the surface magma ocean, which in turn is sensitive to its oxygen fugacity (fO2). Observability estimations and characterization of the atmospheric emission of 55 Cnc e have mostly remained limited to low spectral resolution space-based studies. Here, we aim to examine ground-based high-resolution observabilities of a diverse set of mineral atmospheres produced across a grid of mantle fO2s varying over 12 orders of magnitude. We assume a bulk silicate Earth mantle composition and a substellar dayside temperature of T = 2500 K in the near-infrared wavelength region. This spectral range is often featureless for this class of atmospheres at low resolution. Coupling our newly developed simulator for synthesizing realistic observations from high-resolution ground-based spectrographs (Ratri) to a pre-developed high-resolution cross-correlation spectroscopy (HRCCS) analysis pipeline (Upamana), we find that this array of mineral atmospheres would all be detectable with 11 h of observing time of the dayside of 55 Cnc e with CARMENES and each individual scenario can be correctly differentiated within 1σ. Our analysis is readily able to distinguish between a planet with an Earth-like redox state (with f O2 ∼ 3.5 log10 units above the iron-wustite, ¨ IW buffer) and a Mercury-like planet (fO2 ∼ 5 log10 units below IW). We thus conclude that the HRCCS technique holds promise for cataloguing the diversity of redox states among the rocky exoplanetary population.
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