Exploration of the gas giants

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Peering below Callisto's icy crust with ALMA
https://phys.org/news/2026-01-peering-c ... -alma.html
by Laurence Tognetti, Universe Today

What exists beneath the surface of Jupiter's icy moon, Callisto? This is what a recent study accepted by The Planetary Science Journal hopes to address as a team of researchers investigated the subsurface composition of Callisto, which is Jupiter's outermost Galilean satellite. This study has the potential to help scientists better understand the interior composition of Callisto, which is hypothesized to possess a subsurface liquid water ocean, and develop new techniques for exploring planetary subsurface environments.

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NASA's Juno measures thickness of Europa's ice shell
https://phys.org/news/2026-01-nasa-juno ... a-ice.html
by NASA

Data from NASA's Juno mission has provided new insights into the thickness and subsurface structure of the icy shell encasing Jupiter's moon Europa. Using the spacecraft's Microwave Radiometer (MWR), mission scientists determined that the shell averages about 18 miles (29 kilometers) thick in the region observed during Juno's 2022 flyby of Europa. The Juno measurement is the first to discriminate between thin and thick shell models that have suggested the ice shell is anywhere from less than half a mile to tens of miles thick.

Slightly smaller than Earth's moon, Europa is one of the solar system's highest-priority science targets for investigating habitability. Evidence suggests that the ingredients for life may exist in the saltwater ocean that lies beneath its ice shell. Uncovering a variety of characteristics of the ice shell, including its thickness, provides crucial pieces of the puzzle for understanding the moon's internal workings and the potential for the existence of a habitable environment.

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James Webb Telescope Takes a First Peek Inside Uranus
The planet's upper atmosphere has been mapped for the first time, revealing one of the solar system's most enigmatic members.
By Graham Templeton February 23, 2026

The European Space Agency announced Thursday that a study using the joint NASA/ESA-built James Webb Space Telescope has peered into Uranus's upper atmosphere. It's an important first step in revealing the nature of ice giants both here and elsewhere throughout the universe.

The study focused on the planet's magnetosphere—specifically, the ionosphere, which extends up to 5,000 kilometers above Uranus' cloud tops. Because the ionosphere is predictably full of ions, it is a charged field that interacts strongly with the planet's magnetic field.

This allows the ionosphere to serve as a means of investigating the magnetic field, and, through that, the planet's core and its spectacular auroras.

https://www.extremetech.com/science/jam ... ide-uranus

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New Observations Show Jupiter is Slightly Smaller than Previously Measured!
By Philip Plait
June 22, 2026

Introduction:

(Bad Astronomy) Jupiter is a behemoth. It’s the largest planet in the solar system by far — by volume, all the other planets could fit inside it — and very well studied by planetary scientists.

So you’d think we know its size — that is, its diameter — very accurately. However, the best measurements of its width have an uncertainty of about 4 kilometers. That’s actually pretty good considering Jupiter is about 140,000 km across! But models of its interior depend on the measured diameter, and getting it as nailed down as possible is a big deal.

The thing is, getting this number isn’t easy. For one, Jupiter is far away, and measurements made from Earth just have an inherent uncertainty to them. Also, Jupiter is a gas giant, which means what we see isn’t a solid surface, but the top of its atmosphere. That means there’s no easily observed benchmark (like sea level) to use for the measurements. Worse, in some places we see deeper in to its atmosphere, and in others clouds block that view. To get around that, scientists use a somewhat arbitrary benchmark as a baseline — the 1 bar level, where the pressure of the atmosphere is roughly equal to Earth’s pressure at sea level.

How do you measure that? One way is to observe stars as Jupiter passes in front of them from our point of view; as the starlight passes through the atmosphere it gets bent depending on the density of the gas, and this can be used to find the 1 bar level. Scientists did this decades ago when the Pioneer and Voyager probes passed by the planet, observing radio waves from stars (because visible light is easily blocked by gases in Jupiter’s air, so radio waves give a better view deeper down).

The problem there is that the uncertainty was large, that 4 km number I mentioned earlier. Not bad, but we need better.

Read more here: https://badastronomy.beehiiv.com/p/jup ... -thought