hydrogen atmosphere Archives - Astrobiology

The transit depth excess due to vertical mixing in the exoplanet atmosphere from our 1D chemical kinetics model run (Tequi = 500 − 2000 K; Tint = 150, 250, 350, 450 and 550 K; log10(Kzz) = 9; surface gravity = 1000 cm s−2 ). The color contours from blue to red in panels (a) - (e) represent the transit depth excess due to CH4 and panels (f) - (j) due to NH3 . The white to black colormesh plot in all the panels represent the total transit depth excess. -- astro-ph.EP

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Habitable Zones, Status Report, Water/Hycean Worlds & Oceanography

Signature of Vertical Mixing in Hydrogen-dominated Exoplanet Atmospheres

by Keith CowingOctober 17, 2024October 17, 2024

Vertical mixing is a crucial disequilibrium process in exoplanet atmospheres, significantly impacting chemical abundance and observed spectra. While current state-of-the-art observations have detected its signatures, the effect of vertical mixing […]

Schematic overview of coupled redox-atmosphere-interior evolution model, PACMAN-P. The model is initialized with a completely molten mantle, and the solidification radius, rs, evolves from the core-mantle boundary to the surface, rp, as the planet cools. At each timestep, we calculate multiphase thermochemical equilibrium between C, H, O, and Fe-bearing species to find the mantle redox state and the partitioning of volatiles between the magma ocean and the atmosphere. Surface climate, Tsurf, is calculated using a radiative-convective model given atmospheric volatile inventories. Under highly reducing conditions created by large H2 envelopes, the reaction of H2 with the silicate magma ocean produces metallic iron, that is either sequestered in the core or remains in the mantle (two endmember assumptions). Atmospheric escape is either XUV-limited or diffusion limited depending on stratospheric composition, and under the former regime we calculate the hydrodynamic drag of O and CO. -- astro-ph.EP

Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Status Report, TRAPPIST-1

The Erosion Of Large Primary Atmospheres Typically Leaves Behind Substantial Secondary Atmospheres On Temperate Rocky Planets

by Keith CowingOctober 1, 2024October 1, 2024

Exoplanet exploration has revealed that many–perhaps most–terrestrial exoplanets formed with substantial H2-rich envelopes, seemingly in contrast to solar system terrestrials, for which there is scant evidence of long-lived primary atmospheres. […]

The compatibility of the combined Eureka! spectrum with a wide range of atmospheric compositions and opaque pressure levels. Colored contours show the σ-confidence to which each model can be ruled out by the data. Model spectra permit an offset between the NRS1 and NRS2 detectors as to best fit the data. Panel (a) considers a grid of atmospheres with compositions between 1× and 1000× solar. Panel (b) explores H2-CO2 atmospheres, while panel (c) concerns H2-H2O atmospheres. For an opaque pressure level of 1 bar, the data confidently (> 3-σ) rules out atmospheres with mean molecular weights ≲ 10 g mol−1 in all cases. Smaller mean molecular weights are allowed by the data for lower opaque pressure levels (e.g., 10−4 bar). -- astro-ph.EP

Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

JWST COMPASS: The 3-5 Micron Transmission Spectrum of the Super-Earth L 98-59 c

by Keith CowingSeptember 13, 2024September 18, 2025

We present a JWST NIRSpec transmission spectrum of the super-Earth exoplanet L 98-59 c. This small (Rp=1.385±0.085R⊕, Mp=2.22±0.26R⊕), warm (Teq=553K) planet resides in a multi-planet system around a nearby, bright […]