Ice Giant Archives

The four giant planets as seen by Hubble WFC3/UVIS at different near-UV wavelengths, and processed by Judy Schmidt (note - these images are not shown to scale). The Jupiter and Saturn images are constructed from F343N (red), F275W (green), and F225 (blue), whereas a lack of observations for Uranus and Neptune required us to shift to redder wavelengths: F547M (red), F467M (green), and F336W (blue) for the Ice Giants. Jupiter and Ganymede were observed 2017-02-02 at 12:16UT, Saturn was observed at 2018-06-07 at 00:06UT, Uranus on 2015-08-30 at 10:08UT, and Neptune on 2015-09-02 at 07:58UT. Strong UV absorption is visible at the poles of Jupiter and Saturn due to the nature of highaltitude aerosols and the potential link to auroral chemistry. Red vortices, such as Jupiter’s Great Red Spot and Oval BA (lower left), appear dark due to the blue-absorbing chromophore responsible for their red colours. Uranus’ bright north polar cap of aerosols, and its narrow rings, are just visible in this image. Neptune’s banding, and some bright high clouds (appearing in pink) can be seen in both northern and southern hemispheres. In addition, Saturn’s rings appear reddish due to UV absorption. Credit: NASA/ESA/CSA/Hubble/Judy Schmidt.

Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Gas Giants, Ice Giant, Imaging & Spectroscopy, Jupiter, Neptune, Saturn, Status Report, Uranus

Exploring Giant Planet Atmospheres with Habitable Worlds Observatory

by Keith CowingOctober 22, 2025October 22, 2025

Visible and ultraviolet imaging and spectroscopy of Solar System giant planets can set the paradigm for the atmospheric, ionospheric, and magnetospheric processes shaping the diversity of giant exoplanets, brown dwarfs, […]

Radius evolution for a metal-enriched planet (Z=0.1) as computed with our approach (square points) versus the planetsynth models of M¨uller & Helled (2021) (solid curves; note that they employ a different EOS than us). Red and blue curves correspond to 300 and 32 M⊕ planets (with 10 M⊕ cores), respectively, at an equilibrium temperature 288 K. The giant planet’s cooling curve is in excellent agreement between the two approaches. Lower mass planets however exhibit ∼15% radius discrepancies, possibly due to EOS differences. -- astro-ph.EP

Astrogeology, Exoplanets, -moons, -comets, Ice Giant, Neptune, Status Report

Coupled Planetary Interior and Tidal Evolution

by Keith CowingOctober 10, 2025

We present a new planetary structure/thermal evolution model, designed for use in problems that couple orbital dynamics with planetary structure.

Reprocessed images of Uranus [L]] and Neptune [R] NASA/JPL-Caltech (Uranus and Neptune); “Modelling the Seasonal Cycle of Uranus’s Colour and Magnitude, and Comparison with Neptune,” by Patrick G. J. Irwin et al., in Monthly Notices of the Royal Astronomical Society, Vol. 527, No. 4; February 2024 (reprocessed images)

Astrogeology, Exoplanets, -moons, -comets, Ice Giant, Icy Worlds, Neptune, Status Report, Uranus

Icy or Rocky? Convective Or Stable? New Interior Models Of Uranus and Neptune

by Keith CowingOctober 3, 2025October 3, 2025

We present a new framework for constructing agnostic and yet physical models for planetary interiors and apply it to Uranus and Neptune.

Interstellar object 3I/ATLAS imaged by the Hubble Space Telescope. Could similar objects be the seeds of new planets around young stars? Image credit: NASA/ESA/David Jewitt (UCLA). Image Processing: Joseph DePasquale (STScI). Larger image

Astrogeology, Exoplanets, -moons, -comets, Gas Giants, Ice Giant, Icy Worlds, Interstellar, Press Release

How Interstellar Objects Similar To 3I/ATLAS Could Jump-Start Planet Formation Around Infant Stars

by Keith CowingSeptember 15, 2025September 14, 2025

Interstellar objects like 3I/ATLAS that have been captured in planet-forming discs around young stars could become the seeds of giant planets, bypassing a hurdle that theoretical models have previously been […]

Ariel, Ice Giant, Icy Worlds, Miranda, Missions & Hardware, Oberon, Press Release, Titania, Umbriel, Uranus

The Uranus Flagship: Investigating New Paradigms for Outer Solar System Exploration Workshop Summary Report

by Keith CowingSeptember 2, 2025September 2, 2025

This white paper is a summary of the Uranus Flagship Workshop that took place 21 to 23 May 2024 at NASA’s Goddard Space Flight Center. Co-led by Goddard and Johns […]

Two representative interior models for Uranus and Neptune with four layers: 1) hydrogen and helium, 2) H2O and hydrogen, 3) carbon-nitrogen-hydrogen mixture and 4) the rocky core composed of iron and rock. m specifies the fractional layer masses. The temperatures for B and C type models are printed without and with parenthesis. The dashed lines in the second layer mark the conditions for the transition from liquid to superionic in pure H2O. -- astro-ph.EP

Exoplanets, -moons, -comets, Ice Giant, Icy Worlds, Neptune, Status Report, Uranus

Ab Initio Entropy Calculations of Water Predict the Interiors of Uranus and Neptune to be 15-30% Colder than Previous Models

by Keith CowingAugust 29, 2025August 29, 2025

Ab initio free energy calculations are employed to derive the entropy of liquid and superionic water over a wide range of conditions in the interiors of Uranus and Neptune. The […]

Sub-Neptune exoplanets tend to be much closer to their host star than Earth is to the Sun and are thought to have atmospheres made of steam over layers of an exotic phase of water that behaves like neither gas nor liquid. (Image by Artem Aguichine UC Santa Cruz)

Exoplanets, -moons, -comets, Ice Giant, Icy Worlds, Press Release

New Model Aims To Demystify Steam Worlds Beyond Our Solar System

by Keith CowingAugust 26, 2025

For astrobiologists, the search for life beyond our solar system could be likened to where one would look in a vast desert—essentially, where there’s water. And it turns out that […]

The phase curve of a planet over one rotation at eight different illumination phases. The images at the right show renderings of the planet’s illuminated surface throughout the observation. Each curve represents a different viewing geometry, the observer-planet-star angle, with the corresponding planetary illumination phase shown by the colored circles in the legend. The top (blue) curve shows a fully illuminated planet, while the lower curves show various partial illumination scenarios down to a completely dark planet (purple). The gray curve represents the classical edge-on viewing case exhibiting the full range of phase variations. -- astro-ph.SR

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

Requirements For Joint Orbital Characterization of Cold Giants and Habitable Worlds with Habitable Worlds Observatory

by Keith CowingJuly 30, 2025July 30, 2025

We determine optimal requirements for the joint detection of habitable-zone planets and cold giant planets with the Habitable Worlds Observatory (HWO).

Potential interior structures of Uranus, Neptune, K2-18 b and TOI-270 d if they have undergone hydrogen-water demixing. We note that alternatives models are also possible (see Secs. 3 and 4). For Uranus and Neptune, the sketches correspond to the cases with Toffset = 1100 K, in which both planets are fully demixed. However, we can’t exclude scenarios in which demixing is still ongoing or does not occur at all. The sketch for K2-18 b shows a mini-Neptune scenario with ongoing demixing, while the one for TOI-270 d corresponds to a case of full demixing. -- astro-ph.EP

Ariel Mission, Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Ice Giant, Icy Worlds, Neptune, Status Report, Uranus

The Possibility of Hydrogen-Water Demixing in Uranus, Neptune, K2-18b and TOI-270d

by Keith CowingJuly 13, 2025July 13, 2025

The internal structures of Uranus and Neptune remain unknown. In addition, sub-Neptunes are now thought to be the most common type of exoplanets.

Atmospheric speciation of TRAPPIST-1e at 280 K above a planetary surface with stable condensates for atmospheres originally in equilibrium with a fully molten mantle. In all panels, the curve colours correspond to the gas species listed in the legend and condensate masses are relative to Earth oceans (EO). Upper panels show the percentage of models by dominant species (VMR > 50%) that satisfy the requirement of a minimum mass of (a) Water, (b) Graphite, (c) α-sulfur, and (d) Ammonium chloride. Lower panels illustrate the composition and total pressure of the atmosphere for (e) CO2-rich above a water ocean, (f) CH4-rich above graphite, (g) CO2-rich above α-sulfur, and (h) CH4-rich above ammonium chloride. Median values are indicated by lines and shaded regions bracket the first and third quartiles. Compare to the atmospheric speciation derived from a partially molten mantle in Figure A5. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Gas Giants, Habitable Zones, Ice Giant, Imaging & Spectroscopy, Status Report, TRAPPIST-1

Diversity of Rocky Planet Atmospheres In The C-H-O-N-S-Cl System With Interior Dissolution, Non-ideality, and Condensation: Application to TRAPPIST-1e and Sub-Neptunes

by Keith CowingJuly 6, 2025July 6, 2025

A quantitative understanding of the nature and composition of low-mass rocky exo(planet) atmospheres during their evolution is needed to interpret observations.

Ice Giant

Exploring Giant Planet Atmospheres with Habitable Worlds Observatory

Coupled Planetary Interior and Tidal Evolution

Icy or Rocky? Convective Or Stable? New Interior Models Of Uranus and Neptune

How Interstellar Objects Similar To 3I/ATLAS Could Jump-Start Planet Formation Around Infant Stars

The Uranus Flagship: Investigating New Paradigms for Outer Solar System Exploration Workshop Summary Report

Ab Initio Entropy Calculations of Water Predict the Interiors of Uranus and Neptune to be 15-30% Colder than Previous Models

New Model Aims To Demystify Steam Worlds Beyond Our Solar System

Requirements For Joint Orbital Characterization of Cold Giants and Habitable Worlds with Habitable Worlds Observatory

The Possibility of Hydrogen-Water Demixing in Uranus, Neptune, K2-18b and TOI-270d

Diversity of Rocky Planet Atmospheres In The C-H-O-N-S-Cl System With Interior Dissolution, Non-ideality, and Condensation: Application to TRAPPIST-1e and Sub-Neptunes

PJ Harvey Announces New Song “Voyager”

Fifty Years after Viking: The Promise of Solar System Microbiology and Microbial Ecology

Characterising Transiting Exoplanets At Long Orbital Period: Lessons Learned For PLATO From 10 Years Of Monitoring The HIP41378 System

Implications Of Self-consistent H2O Ice Optical Constants On Radiative Transfer Models Of Disks

The GAPS Programme at TNG LXXIV. A Reanalysis Of The Planetary Systems TOI-1272 And TOI-1694 With HARPS-N And Retraction Of The Planetary Interpretation Of TOI-1272 c