![Mass-radius diagram of known exoplanets together with model curves taken from A. Aguichine et al. (2021) and L. Zeng et al. (2019). Exoplanet data shown with colored dots were taken from the NASA Exoplanet Archive (J. L. Christiansen et al. 2025) on April 2, 2026. The transiting exoplanets in the HD 191939 system are highlighted with larger markers, error bars and a red outline.-- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/08/The-SPACE.png?resize=1200%2C714&ssl=1)
[astro-ph.EP] The atmospheres of sub-Neptunes provide a window into their internal structure and history, shedding light on the origin of this common, but enigmatic, class of exoplanets.
atmosphere
![Illustration of the TRAPPIST-1 system and the most recent JWST constraints on planetary atmospheres. Planet size and distance roughly to scale. - [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/08/veiled.png?resize=1200%2C820&ssl=1)
Posted inTRAPPIST-1
Veiled in Starlight: Impacts of Stellar Contamination On Retrievals of TRAPPIST-1f’s Atmospheric Composition
[astro-ph.EP] The TRAPPIST-1 system offers seven terrestrial exoplanets with tight orbits and large radii ratios to the host star. If an atmosphere exists, transmission spectroscopy can be used to detect […]
Posted inExoplanets, -moons, -comets
Exploration Of Exoplanet Atmospheres With The James Webb Space Telescope
[astro-ph.EP] The James Webb Space Telescope (JWST) is providing transformative characterization capabilities for the study of both transiting and directly imaged extrasolar planets. Observations deep into the infrared in the […]
Posted inAtmospheres, Climate, Weather
MarsCast: Transfer Learning Of AI Weather Foundation Models To Planetary Atmospheres
[astro-ph.EP] We investigate the transferability of Earth weather foundation models to planetary atmospheres by adapting the GraphCast graph neural weather forecasting model to Mars. While GraphCast achieves state-of-the-art performance for […]
Posted inJupiter
Self-consistent 1D Modelling Of Jupiter’s Upper Atmosphere As An Exoplanet Analogue
[astro-ph.EP] Jupiter’s upper atmosphere provides a real-world laboratory for validating first-principles models of giant gaseous exoplanets and for constraining the key physical processes that govern them.
![Average ion velocity and magnetic field distributions near the ICB. (A) The center-of-mass velocity of heavy ions in the XZMSE plane, averaged over −1 RM < YMSE < 1 RM. (B) Proton velocity. (C) Velocity shear between protons and heavy ions. (D) Magnetic field strength. (E) Angle between the magnetic field and the X�⃗ MSEin the YZMSE plane, averaged over −1.5 RM < XMSE < 0.5 RM. Black arrows in (A) to (C) indicate velocity directions. Black curves in (A) to (D) mark the nominal locations of the bow shock and ICB. The black shaded sphere in (E) denotes the planetary shadow. -- [physics.space-ph]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/08/Simultaneous.png?resize=1200%2C720&ssl=1)
Posted inSpace Weather & Heliophysics
Simultaneous Mars-orbit Observations Reveal Kelvin-Helmholtz Instability-driven Bulk Atmospheric Ion Escape
[physics.space-ph] Atmospheric ion escape driven by the solar wind is a key process controlling the long-term loss of the Martian atmosphere. Localized plasma clouds can carry substantial fluxes of planetary […]
![[LEFT]: Schematic of the star–planet–observer geometry defining the phase angle α, measured between the star–planet and planet–observer directions. The hemisphere of the planet facing the star is fully illuminated (gold) at all times, while the opposite hemisphere remains in shadow. The observer sees only the portion of the illuminated hemisphere that is visible at a given α, with full illumination visible only at α = 0◦. [RIGHT]: Illustration of planetary phases along an edge-on orbit, with the star at the center and the observer direction indicated below the orbit. Although the star-facing hemisphere remains illuminated throughout the orbit, the visible fraction of this hemisphere changes with phase angle. Full phase occurs at α = 0◦, quadrature at α = 90◦, and new phase at α = 180 , with gibbous and crescent phases spanning the intermediate ranges. -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/08/The-Impact.png?resize=1200%2C714&ssl=1)
Posted inAstronomy & Telescopes
The Impact of Planetary Phase Functions On Exo-Earth Detectability With EXOSIMS
[astro-ph.EP] The under-development NASA Habitable Worlds Observatory (HWO) aims to provide breakthroughs in exoplanet science, yet the most effective approaches to modeling the detection and characterization of potentially Earth-like worlds […]
Posted inExoplanets, -moons, -comets
ESCAPE: A Small Explorer Mission To Study The Stellar Drivers Of Exoplanet Evolution
[astro-ph.EP] The long-term stability of exoplanetary atmospheres depends critically on the extreme-ultraviolet (EUV) photon and high-energy particle fluxes from the host star, which are poorly constrained.
![Left: Orbital separations of inspiralling planets over time. Right: Mass accreted onto planets over time. For each initial planet mass, we show results for 𝜀 ∈ [0.01, 0.1, 0.3, 0.5, 1.0], with an increasing efficiency denoted by an increasing opacity. We also allow the accretion to increase up to 10× the Eddington limit, denoted by the dotted lines. Accretion stops when 𝑅𝐵 < 𝑅Jup (see §2.3). -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/08/Atmospheric-Signatures.png?resize=1200%2C722&ssl=1)
Posted inExoplanets, -moons, -comets
Atmospheric Signatures of Common Envelope Evolution in White Dwarf Planets
[astro-ph.EP] The majority of confirmed exoplanets orbit within 1 au of a main-sequence (MS) star. When their stellar hosts evolve off the MS, many of these planets will be engulfed […]
Posted inVenus
Development Of A Data Retrieval Algorithm For Venus Nephelometry In Preparation For The Rocket Lab Mission To Venus
[Science Direct] The Rocket Lab Mission to Venus (RLMV) will carry a single primary instrument, the Autofluorescence Nephelometer (AFN), to interpret atmospheric particle properties from light-scattering measurements. This process is […]