Neptune Archives

Astrochemistry, Astrogeology, Exoplanets, -moons, -comets, Ice Giant, Missions & Hardware, Neptune, Status Report, Uranus

Ice Giants Pre-Decadal Survey Mission Study Report

by Keith CowingNovember 20, 2025November 19, 2025

The Ice Giants Study was commissioned by NASA to take a fresh look (as of 2017) at science priorities and concepts for missions to the Uranus and Neptune systems in […]

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.

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.

We present the discovery by the TESS mission of one transiting Neptune-sized planet, TOI-6223 b and two transiting super-Earths, TOI-1743 b and TOI-5799 b. We validate these planets using a statistical validation method, multi-color light curves and other ancillary observations. astro-ph.EP

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

TOI-1743 b, TOI-5799 b, TOI-5799 c and TOI-6223 b: TESS Discovery And Validation Of Four Super-Earth To Neptune-sized Planets Around M dwarfs

by Keith CowingSeptember 19, 2025September 19, 2025

We combined TESS and ground-based photometric data to constrain the physical properties of the planets. TOI-6223-b is slightly larger than Neptune (Rp=5.12+0.24−0.25 R⊕) orbiting an early M dwarf in 3.86 […]

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 […]

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.

Astrogeology, Atmospheres, Climate, Weather, Ice Giant, Icy Worlds, Imaging & Spectroscopy, Neptune, Status Report, Uranus

Different Inhomogeneous Evolutionary Histories for Uranus and Neptune

by Keith CowingJune 19, 2025

We present updated non-adiabatic and inhomogeneous evolution models for Uranus and Neptune, employing an interior composition of methane, ammonia, water, and rocks.

Binary collision-induced H2–He absorption coefficient, α, normalized by the hydrogen and helium gas densities, as function of frequency in the fundamental band, at 296 K. The parato-ortho distribution, is representative of equilibrium H2, just as in Fig. 2. Our model (“this work”), is compared with the model of Abel et al.17 for T = 300K, and with the laboratory measurements of Vitali et al. 18 and Brodbeck et al.19 , both of which were made near 296 K. We note that neither our model nor that of Abel et al. considered the discrete, intercollisional interference dips present in the laboratory spectra. -- astro-ph.EP

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Gas Giants, Ice Giant, Jupiter, Neptune, Saturn, Status Report, Uranus

Improved H2-He and H2-H2 Collision-Induced Absorption Models and Application to Outer-Planet Atmospheres

by Keith CowingJune 15, 2025June 13, 2025

Using state-of-the-art ab initio interaction-induced dipole and potential-energy surfaces for hydrogen-helium (H2-He) pairs, we compute the rototranslational collision-induced absorption coefficient at 40-400 K for frequencies covering 0-4000 cm-1.

Neptune

Ice Giants Pre-Decadal Survey Mission Study Report

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

Exploring The Sub-Neptune Frontier With JWST

TOI-1743 b, TOI-5799 b, TOI-5799 c and TOI-6223 b: TESS Discovery And Validation Of Four Super-Earth To Neptune-sized Planets Around M dwarfs

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

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

Different Inhomogeneous Evolutionary Histories for Uranus and Neptune

Improved H2-He and H2-H2 Collision-Induced Absorption Models and Application to Outer-Planet Atmospheres

Tricorder Tech: New Handheld Device Maps Chemical Composition Using Infrared Light

No Statistically Significant Evidence For A Correlation Between Stellar And planetary Composition

Water Planet Recon: How Accurately Can We Measure Earth Ocean’s Deepest Point?

Webb Reveals A Stunning Panorama Of Star Formation

Deep Learning of SHERLOC Raman Spectra For Facilitating Mars Astromaterial Identification