habitability Archives

Parameter space showing the effect of GR on eccentricity oscillations due to an exterior planetary companion for a variety of combinations of the mass ratio m2/m1 and semi-major axis ratio a2/a1. The interior planet was assumed to be a 1 M⊕ planet at 0.01 AU. When ξ < 1 (bottom-left, red), GR amplifies eccentricity oscillations; when ξ > 1 (top-right, black), GR suppresses them. The dashed line marks the transition as derived in F. C. Adams & G. Laughlin (2006). -- astro-ph.EP

Exoplanets, -moons, -comets, Habitable Zones, Status Report, Stellar Cartography

General Relativity Can Prevent a Runaway Greenhouse on Potentially Habitable Planets Orbiting White Dwarfs

by Keith CowingOctober 1, 2025October 1, 2025

Planets orbiting in the habitable zones of white dwarfs have recently been proposed as promising targets for biosignature searches.

The modelled angular velocity evolution of stars of different masses, initial rotation periods and metallicities. The masses considered are 0.5𝑀 (left panel), 0.7𝑀 (middle panel) and 1𝑀 (right panel). The initial periods considered are 1 day (dashed lines) and 10 days (solid lines). The metallicities considered are -1 dex (dark blue lines), -0.5 dex (purple lines), 0 dex (orange lines) and +0.5 dex (yellow lines). The point at which the star transitions from the saturated to unsaturated regime (at Rocrit = 0.2) is indicated by a triangle along each track. -- astro-ph.EP

Astrochemistry, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Habitable Zones, Space Weather & Heliophysics, Status Report

Modelling The Effect Of Stellar Metallicity On The XUV Evolution Of Low-mass Stars and its Impact on Exoplanet Atmospheres/habitability

by Keith CowingSeptember 29, 2025September 28, 2025

Understanding how exoplanet atmospheres evolve is a key question in the context of habitability. One key process governing this evolution is atmospheric evaporation by stellar X-ray and EUV emission (collectively, […]

A classification scheme for volatile-rich sub-Neptunes. The schematic compares different types of sub-Neptunes with H2 and H2O dominated atmospheres as a function of the equilibrium temperature and H2 content. Ice worlds: Cold subNeptunes where any water is frozen in a layer of ice atop high-pressure ice, with a thin H2-dominated atmosphere (65). Hycean worlds: Warmer than ice worlds, hycean worlds have a thin H2-rich atmosphere overlying an ocean of liquid water, which itself is above a layer of high-pressure ices. These planets have the potential to support habitable conditions (9). Mini-Neptunes: Sub-Neptunes with a deep H2-rich atmosphere followed by a mixed H2O-H2 supercritical layer below before reaching a layer of high-pressure ice and then a core (17, 65). Steam worlds: Water worlds with H2O dominated atmospheres. At equilibrium temperatures above Tcrit, a high proportion of H2O exists in the atmosphere, with a supercritical mixed-envelope at higher pressures. Supercritical mini-Neptunes: These planets are hotter than Tcrit, and contain interiors where H2 gas is highly soluble in supercritical H2O (46, 65). This mixed-envelope would lie over a layer of high-pressure ice above the core. Legend: The legend at the top shows the different compositions corresponding to the colors in the schematic, including the core, different phases of H2O and envelope composition; high-P ice refers to high-pressure ice. Note that the core has further distinct layers but we do not label them here. Sharp phase transitions are shown for ice-atmosphere and ocean-atmosphere transitions. Other phase transitions are marked by a gradient, as they may not be sharp phase transitions (83). -- astro-ph.EP

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

Exploring The Sub-Neptune Frontier With JWST

by Keith CowingSeptember 25, 2025September 25, 2025

Sub-Neptune planets, with sizes and masses between those of Earth and Neptune, dominate the exoplanet population.

This chart shows, on the top row, artist concepts of the seven planets of TRAPPIST-1 with their orbital periods, distances from their star, radii, masses, densities and surface gravity as compared to those of Earth. Credit: NASA/JPL-Caltech (larger image)

Analog Studies, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Desert Worlds, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Status Report, TRAPPIST-1

Born Dry or Born Wet? A Palette of Water Growth Histories in TRAPPIST-1 Analogs and Compact Planetary Systems

by Keith CowingSeptember 23, 2025September 23, 2025

It is still unclear whether exoplanets in compact multiplanet systems such as TRAPPIST-1 are able to accrete large quantities of volatiles, grow to sufficient mass, and maintain robust atmospheres and […]

Surface (top row) and cloud (bottom row) distributions for our various Snowball Earth models. The surface was either modeled as a fully ice-covered “Hard Snowball” (top left) or contained a tropical ocean belt to simulate a “Slushball Earth” scenario (top right). Low-altitude water ice clouds (light blue) could have existed in an equatorial belt during summer months (bottom left) or only in the southern hemisphere during winter months. In winter these low-level clouds could have been fully covering the hemisphere (bottom middle left), scattered throughout the hemisphere (bottom middle right), or scattered throughout with additional high-altitude (grayish-blue) water ice clouds (bottom right). -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Mars, Status Report

Polarized Signatures of Variable Worlds: Modeling Heterogeneous Habitable Earth- and Early Mars-like (Exo)planets

by Keith CowingSeptember 23, 2025September 23, 2025

Determining the habitability of terrestrial exoplanets is a complex problem that represents the next major step for the astrophysical community.

Diverse density and composition of small exoplanets. The plot shows M-dwarf planets that have precision mass and radius measurements (Luque & Palle´ 2022). Small planets of FGK stars also occupy a broad parameter space that spans from Earth composition to water worlds or planets with massive H/He envelopes (Parc et al. 2024). The planets in the 1.4 – 2.6 Earth’s radius range can be large rocky planets, water worlds, or having massive H/He envelopes (Luque & Palle´ 2022; Rogers et al. 2023). The figure is adapted from Rogers et al. (2023) with permission. -- astro-ph.IM

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report

Identifying Rocky Planets And Water Worlds Among Sub-Neptune-sized Exoplanets With The Habitable Worlds Observatory

by Keith CowingSeptember 23, 2025September 23, 2025

Astronomers are debating whether the plentiful “sub-Neptune” exoplanets — worlds a bit larger than Earth but smaller than Neptune — are predominantly rocky planets, water-rich “ocean worlds,” or gas-enshrouded mini-Neptunes.

Selected examples of observed polarized Earthshine spectra, along with corresponding simulations of reflected and polarized light, as presented in Appendix B. For each spectrum, we include a simulated observation image, fit the power-law slopes γ, and report the RMSE between simulations and observations. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Moon, Press Release

Planet Earth In Reflected And Polarized light – III. Modeling And Analysis Of A Decade-long Catalog Of Earthshine Observations

by Keith CowingSeptember 22, 2025September 22, 2025

Earthshine observations offer a unique opportunity to study Earth as an exoplanet seen from the Moon. As the Sun-Earth-Moon geometry changes, Earth can be observed as a spatially unresolved exoplanet […]

Large enough to retain an atmosphere and drive geologic/hydrologic cycles, but not so massive that relocation is infeasible. This figure illustrates why planet size and escape velocity are critical factors for habitability. It plots the radius of planets (relative to Earth) on the horizontal axis and their escape velocity (in km/s) on the vertical axis. Escape velocity is the minimum speed an object needs to break free from a planet’s gravitational pull. -- astro-ph.EP

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report

Toward Alternative Earths’ Habitability of Solar System Bodies at Earth’s Orbit

by Keith CowingSeptember 15, 2025September 14, 2025

This paper presents the first structured evaluation of Solar System bodies hypothetically relocated to Earth orbit (1 AU) to assess their potential as alternative habitats.

[LEFT] Best value of the minimum probability for each cosmology scenario-habitability condition pair mentioned in the text. For each element in this chart, the minimum probability of the best combination of habitability conditions of all those which include the one mentioned is displayed. The top row includes combinations of up to 8 habitability conditions; the rest are capped at 5.[RIGHT] Same - but comparing against origin of life scenarios. -- astro-ph.CO

Astrochemistry, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biophysics, Biosignatures & Paleobiology, Habitable Zones, Status Report

Multiverse Predictions for Habitability: Fundamental Physics and Galactic Habitability

by Keith CowingSeptember 15, 2025September 14, 2025

In the multiverse hypothesis, a range of universes exist with differing values of our physical constants.

An artist’s impression of our Milky Way Galaxy, showing the location of the Sun. Our Solar System is about 27,000 light years from the centre of the galaxy. The nearest technological species could be 33,000 light years away. Image credit: NASA/JPL–Caltech/R. Hurt (SSC–Caltech). Larger image

Astronomy & Telescopes, Biosignatures & Paleobiology, Intelligence & Language, Press Release, SETI & Technosignatures

How Common Are Biological ETIs in the Galaxy?

by Keith CowingSeptember 12, 2025September 12, 2025

The closest technological species to us in the Milky Way galaxy could be 33,000 light years away and their civilisation would have to be at least 280,000 years, and possibly […]

habitability

General Relativity Can Prevent a Runaway Greenhouse on Potentially Habitable Planets Orbiting White Dwarfs

Modelling The Effect Of Stellar Metallicity On The XUV Evolution Of Low-mass Stars and its Impact on Exoplanet Atmospheres/habitability

Exploring The Sub-Neptune Frontier With JWST

Born Dry or Born Wet? A Palette of Water Growth Histories in TRAPPIST-1 Analogs and Compact Planetary Systems

Polarized Signatures of Variable Worlds: Modeling Heterogeneous Habitable Earth- and Early Mars-like (Exo)planets

Identifying Rocky Planets And Water Worlds Among Sub-Neptune-sized Exoplanets With The Habitable Worlds Observatory

Planet Earth In Reflected And Polarized light – III. Modeling And Analysis Of A Decade-long Catalog Of Earthshine Observations

Toward Alternative Earths’ Habitability of Solar System Bodies at Earth’s Orbit

Multiverse Predictions for Habitability: Fundamental Physics and Galactic Habitability

How Common Are Biological ETIs in the Galaxy?

NASA Comments On The Future Of Astrobiology

AI-Run Growth Chamber Will Test How Plants Develop in Microgravity Against a Matching Experiment on Earth

Perseverance Rover Offers Clues to Protect Crews From Mars Dust

NASA Spaceline Current Awareness List #1,222 23 October 2026 (Space Life Science Research Results)

A Neural-network Model To Find Correlations In Astrochemical Space