hydrogen-rich atmosphere Archives - Astrobiology

Mass versus radius diagram for 261 archive planets

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Status Report

The Influences of Hydrogen-Silicate-Iron Miscibility on the Demographics of Sub-Neptunes and Super-Earths

by Keith CowingMay 1, 2026May 1, 2026

Models based on variable miscibility among hydrogen, molten silicate, and molten iron, coupled with atmospheric escape, can reproduce the observed occurrence density structure of sub-Neptunes and super-Earths in mass-radius space.

Black points are the sample of the planetary formation dataset provided by Kimura & Ikoma (2022) in the phase space of ∆a = 0.005AU, ∆Mp = 0.5M⊕. Two-dimensional probability density distribution of the initial water content and hydrogen-rich atmospheric mass for GJ 486b analogs, constructed using Gaussian kernel density estimation (KDE). The water content axis is sampled logarithmically and the atmospheric mass axis is sampled linearly to properly account for the dynamic range of the variables. The red overlaid ellipse represents the 3σ confidence region derived from the covariance matrix, indicating the principal dispersion of the sample distribution. -- astro-ph.EP

Astrochemistry, Astrogeology, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report, Water/Hycean Worlds & Oceanography

Inversion of Hydrogen-rich Atmosphere and Water Content for GJ 486b

by Keith CowingApril 23, 2026April 23, 2026

GJ-486b is a close-in planet orbiting an M dwarf and is therefore expected to have undergone strong atmospheric escape. Motivated by theoretical and observational studies on the constraints of its […]

Surface temperatures Tsurf (𝑋C+O, C/O) for varying Psurf (from left to right: 1, 10, and 100 bar). For comparability, the internal temperatures Tint (185, 104, and 56 K, respectively) were chosen such that the minimum Tsurf for each pressure is at the freezing point of water, 273 K. For this, Tsurf(Tint) was linearly interpolated. -- MNRAS

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Habitable Zones, Press Release, Water/Hycean Worlds & Oceanography

A Hydrogen Atmosphere Could Keep Exomoons Habitable For Billions Of Years

by Keith CowingMarch 12, 2026March 12, 2026

Liquid water is considered essential for life. Surprisingly, however, stable conditions that are conducive to life could exist far from any sun.

A snapshot of the DeepBL hr simulation, showing (from upper left, going clockwise): cloud condensate, vertical velocity, specific humidity, and precipitating water. The colorbar for all fields except for vertical velocity is the base-10 logarithm of the water mass fraction (i.e., a value of -5 means 10−5 kg/kg.) Note that this simulation was performed on a quasi-2D grid, and with a higher resolution than the rest of our simulations. An animation of this simulation is available in the Supplemental Movie. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Status Report, Water/Hycean Worlds & Oceanography

Resolved Convection In Hydrogen-rich Atmospheres

by Keith CowingDecember 16, 2024December 16, 2024

In hydrogen-rich atmospheres with low mean molecular weight (MMW), an air parcel containing a higher-molecular-weight condensible can be negatively buoyant even if its temperature is higher than the surrounding environment.

Radiative cooling rate per molecule under optically thin and LTE conditions as a function of temperature. The upper panel shows the cooling rates of C-bearing species, while the lower panel displays those of H- and O-bearing species, respectively. The net radiative cooling rate of each species is calculated by summing the cooling rate for each energy transition (Equation (12) in Supplementary Information), with reference to line data provided by HITRAN and ExoMol database. -- astro-ph.EP

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

Suppression of Hydrodynamic Escape of an H2-rich Early Earth Atmosphere by Radiative Cooling of Carbon Oxides

by Keith CowingNovember 27, 2024September 18, 2025

Radiative cooling by molecules is a crucial process for hydrodynamic escape, as it can efficiently remove the thermal energy driving the outflow, acquired through X-ray and extreme UV absorption. Carbon […]

Panel A: Schematic representation for the formation of the Fe vacanciess on the (011)FeS surface. Panel B: optimized geometries for the original, non-defective, slab, the slab with a single Fe vacancy and the slab with two Fe vacancies (S atoms are in yellow and Fe atoms in orange). Fe atoms highlighted in blue colour are the ones removed on the process. S atoms highlighted in red are the most reactive ones in each structure. -- astro-ph.SR)

Astrochemistry, Astrogeology, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Meteorites & Asteroids, Press Release

Reactivity Of Chondritic Meteorites Under H2-rich Atmospheres: Formation Of H2S

by Keith CowingOctober 31, 2024October 31, 2024

Current models of chemical evolution during star and planetary formation rely on the presence of dust grains to act as a third body.

The product of the heating efficiency (η) and (Rxuv/Rp) 2 . The product was obtained by equating the hydrodynamic results with energy-limited formula. Left panel: planets orbiting G-type stars. Right panel: planets orbiting M-type stars. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Gaia - Planetary Perspectives, Status Report, Water/Hycean Worlds & Oceanography

Characterization Of The Regimes Of Hydrodynamic Escape From Low-mass Exoplanets

by Keith CowingMay 31, 2024May 31, 2024

The hydrodynamic escape driven by external or internal energy sources sculpts the population of low mass close-in planets. However, distinguishing between the driving mechanisms responsible for the hydrodynamic escape of […]