![Cartoon illustrating the effect of the runaway greenhouse transition on atmospheric composition for two rocky planets with identical He, H2O and CO2 inventories. With a thin He atmosphere, planets below the runaway greenhouse limit (right) will have He-rich upper atmospheres and may support surface liquid water. For planets inside the inner edge of the habitable zone (left), H2O from liquid water oceans and CO2 from carbonates are transported into the atmosphere, dramatically decreasing the scale height and making the transit spectrum of the planet flatter. -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/07/Climates-of-temperate.png?resize=1200%2C720&ssl=1)
[astro-ph.EP] We present radiative-convective modeling of rocky exoplanets with He-dominated atmospheres and low envelope mass fractions. Helium has a steeper adiabatic temperature profile than N2 and H2 as it has […]
Atmospheres, Climate, Weather
![Best-fitting spectrum and atmospheric properties of WD 1856 b. a. Spectral decomposition illustrating the model components required to explain WD 1856 b’s JWST transmission spectrum (FIREFLy reduction; orange circles with 1 σ error bars). The best-fitting model (black curve) contains absorption from multiple CH4 features (purple shading), H2 + He continuum absorption (dark grey shading), and tentative evidence of C2H6 near 3.4 µm (brown shading) and PH3 near 4.3 µm (orange shading). Aerosol continuum opacity (silver shading) blocks thermal emission from the deep atmosphere in windows between CH4 bands, obscuring the ‘negative spikes’ that would otherwise be observed near 0.7 µm, 2.9 µm, and longwards of 4.0 µm for a clear atmosphere. The best-fitting model without nightside thermal emission (blue dashed curve) cannot explain the significantly lower transit depths longwards of 3.5 µm. b. Retrieved atmospheric properties, planetary mass, and aerosol properties from WD 1856 b’s JWST transmission spectrum for the FIREFLy (orange histograms) and Juniper (green histograms) data reductions. The median (solid line) and 1 σ credible intervals for each parameter (dashed lines) are overlaid. c. Residuals between the data and best-fitting model. -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/07/Aerosols.png?resize=1200%2C719&ssl=1)
Posted inAtmospheres, Climate, Weather
Aerosols And Hydrocarbons In The Atmosphere Of A White Dwarf Planet
[astro-ph.EP] Most stars, including our Sun, will one day evolve into red giants and, subsequently, white dwarfs. Several planet candidates have recently been identified orbiting white dwarfs, demonstrating that planets […]
Posted inExtinction events
Researchers Confirm The Cause Of Earth’s Biggest Mass Extinction
[Stanford University] A new Stanford-led study offers the clearest picture yet of how some ocean life survived our planet’s biggest mass extinction while most animals did not.
![Schematic showing the thermal and atmospheric escape evolution of two interpretations of sub-Neptune interiors. In a standard planetary model, a silicate interior is distinct from a hydrogen-rich envelope. As the planet contracts, hydrogen is removed from the upper atmosphere via stellar heating, and the interior-envelope boundary does not significantly contract with time. The temperature at this interface can reach of order ∼ 10, 000 K at early ages. In the miscible model, the interior-envelope boundary is defined by a binodal surface, which delineates regions in which hydrogen and silicate are miscible or immiscible. The temperature at the binodal surface does not change significantly with time. The radial position of the binodal surface contracts with time, exsolving hydrogen into the base of the envelope, while hydrogen is also removed from the top of the upper atmosphere.-- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/07/Testing-the.png?resize=1200%2C716&ssl=1)
Posted inExoplanets, -moons, -comets
Testing The Prevalence Of Hydrogen-silicate Miscibility In Young Sub-Neptunes
[astro-ph.EP] Hydrogen-silicate miscibility can significantly alter the interior structure and thermal evolution of sub-Neptunes. We consider the interplay between this miscibility and stellar-driven atmospheric escape.
Posted inAstrogeology
Ancient Rocks Reveal How Water Shaped Earth 3.1 Billion Years Ago
[Adelaide University] Geologists studying some of the planet’s oldest volcanic rocks have uncovered new evidence that water was playing a major role in shaping Earth’s interior and driving volcanic activity […]
Posted inMars
Water Ice Inside A Martian Crater
[ESA] Like a sprinkle of powdered sugar on a rich red velvet cake, this scene from the ESA/Roscosmos ExoMars Trace Gas Orbiter captures the contrasting colours of bright white water-ice […]
Posted inMars
Hematite Is A Mineralogical Marker Of Ancient Climate Change On Mars
[Science via PubMed] The ancient climate of Mars changed from warm to cold surface conditions. This climate transition is demonstrated by geomorphological evidence but lacks suitable mineralogical indicators.
Posted inBiosignatures & Paleobiology
White Paper On Phototrophic Biosignatures: Research Priorities For The Search For Life On Other Worlds
[astro-ph.IM] Photosynthesis is of prime interest in the telescopic search for life beyond the Solar System, because, on Earth, oxygenic photosynthesis produces two strong “biosignatures,” global scale signs of life […]
Posted inBiosignatures & Paleobiology
Orbital Biosignature Assay: Phytoplankton Blooms In The Black Sea
[NASA] The turquoise color is likely caused by coccolithophores, a type of phytoplankton covered with calcium carbonate plates that can give surface waters a milky-blue appearance. These types of phytoplankton […]
Posted inExoplanets, -moons, -comets
The Mid-Infrared Transmission Spectrum of the Temperate Sub-Neptune TOI-270 d
[astro-ph.EP] Observations of temperate sub-Neptunes with JWST have ushered in a new era for atmospheric characterization of small exoplanets.