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A Secondary Atmosphere On The Rocky Exoplanet 55 Cancri e

By Keith Cowing
Status Report
astro-ph.EP
May 11, 2024
Filed under , , , , , , , , ,
A Secondary Atmosphere On The Rocky Exoplanet 55 Cancri e
Self-consistent atmosphere models of 55 Cnc e. The NIRCam relative eclipse depths are offset to a mean depth of 60 ppm. Previous Spitzer measurements 24 are shown in gray. The black dashed lines are blackbody models at the temperatures indicated in the plot. The vaporized-rock model was simulated using the rocky composition that corresponds to the bulk silicate Earth; using other plausible rock compositions results in qualitatively similar results (Extended Data Fig. 7). The atmosphere models are simulated either in a parameter exploration of CHONSP elemental abundances or with the assumption of volatile equilibrium with an underlying magma ocean. The models shown are selected from those that provide adequate fits to the data. The volatile atmosphere models with enhanced outgassing of rock-forming elements can cause substantial changes in the eclipse depth and the emission spectra. The models are smoothed to R=100 for the clarity of illustration. Model results binned to the same wavelength channels as the MIRI data are shown as colored points. The oxygen fugacity (fO2 ) describes the redox condition of the magma and fO2=IW-4 means a condition more reduced than the iron-wustite (IW) buffer by 4 orders of magnitude. The full sets of atmospheric models are described in Methods and Extended Data Figs. 8 and 9. — astro-ph.EP

Characterizing rocky exoplanets is a central endeavor of astronomy, and yet the search for atmospheres on rocky exoplanets has hitherto resulted in either tight upper limits on the atmospheric mass or inconclusive results.

The 1.95-REarth and 8.8-MEarth planet 55 Cnc e, with a predominantly rocky composition and an equilibrium temperature of ~2000 K, may have a volatile envelope (containing molecules made from a combination of C, H, O, N, S, and P elements) that accounts for up to a few percent of its radius.

The planet has been observed extensively with transmission spectroscopy, and its thermal emission has been measured in broad photometric bands. These observations disfavor a primordial H2/He-dominated atmosphere but cannot conclusively determine whether the planet has a secondary atmosphere. Here we report a thermal emission spectrum of the planet obtained by JWST’s NIRCam and MIRI instruments from 4 to 12 um.

The measurements rule out the scenario where the planet is a lava world shrouded by a tenuous atmosphere made of vaporized rock, and indicate a bona fide volatile atmosphere likely rich in CO2 or CO. This atmosphere can be outgassed from and sustained by a magma ocean.

Renyu Hu, Aaron Bello-Arufe, Michael Zhang, Kimberly Paragas, Mantas Zilinskas, Christiaan van Buchem, Michael Bess, Jayshil Patel, Yuichi Ito, Mario Damiano, Markus Scheucher, Apurva V. Oza, Heather A. Knutson, Yamila Miguel, Diana Dragomir, Alexis Brandeker, Brice-Olivier Demory

Comments: Published online in Nature on May 8, 2024. this https URL. Authors’ preprint
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2405.04744 [astro-ph.EP] (or arXiv:2405.04744v1 [astro-ph.EP] for this version)
Related DOI:
https://doi.org/10.1038/s41586-024-07432-x
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Submission history
From: Renyu Hu
[v1] Wed, 8 May 2024 01:17:26 UTC (5,230 KB)
https://arxiv.org/abs/2405.04744

Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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