Scientists at the University of Zurich have presented a new numerical framework that challenges the traditional view of Uranus and Neptune as clearly "ice-rich" worlds. Led by PhD student Luca Morf and initiated by professor Ravit Helled, the team combined physics-based and empirical approaches to produce interior models that are both physically consistent and deliberately "agnostic" about prior assumptions.
The method begins with a random density profile for a planet's interior. For each profile the team computes the gravitational field that best matches observational data, then infers a compatible composition. They repeat this cycle many times and retain solutions that fit the observations. The resulting range of models shows the two blue planets need not be dominated by ice (usually represented by water); some solutions are rock-rich while others are water-rich. Helled notes the idea was first suggested nearly 15 years ago, and the new framework can now demonstrate it numerically.
The study also offers a plausible account of the planets' unusual magnetic fields. The models include so-called "ionic water" layers that generate magnetic dynamos in positions that explain the observed non-dipolar, multi-pole fields. The team finds that Uranus' magnetic field originates deeper than Neptune's. However, uncertainty about how materials behave under the extreme pressures and temperatures inside these planets could affect the conclusions. The authors say current data cannot distinguish the models and call for dedicated missions to Uranus and Neptune to reveal their true nature. The research appears in Astronomy & Astrophysics; source: University of Zurich.
- New modelling combines physics and empirical data.
- Interiors could be rock-rich or water-rich.
- Models help explain non-dipolar magnetic fields.
Difficult words
- framework — a system of methods and ideas used
- agnostic — not committed to one belief or assumption
- density — amount of mass per unit volume
- gravitational field — region where gravity affects objects around a body
- composition — the substances or materials that form something
- ionic water — water in a charged, electrically conducting state
- dynamo — a mechanism that generates a magnetic fielddynamos
- distinguish — to recognize or show a difference between things
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- Why do the authors call for dedicated missions to Uranus and Neptune, and what could such missions reveal?
- How might uncertainty about material behaviour at extreme pressures and temperatures change the study's conclusions?
- If you planned a mission to test these interior models, which measurements would you prioritise and why?
Related articles
Cleaner air in East Asia linked to faster global warming
A study in Nature Communications, Earth and Environment finds recent reductions in aerosol pollution across East Asia, especially China, have probably contributed to faster global surface warming since about 2010. Experts say urgent cuts to emissions and more adaptation finance are needed.
Glacial lakes and flood risk in the Hindu Kush‑Himalaya
The Hindu Kush‑Himalaya stores large freshwater in mountain glaciers. Warming has formed thousands of glacial lakes and raised the risk of sudden outburst floods; experts say better data sharing, observation and funding are needed but political and technical barriers remain.
Jaw membrane in ancient Thrinaxodon may be an early eardrum
Researchers used CT scans and engineering simulations on a Thrinaxodon fossil. Their models show a membrane in the jaw could work as an eardrum, pushing the origin of sensitive mammal hearing back by nearly 50 million years.
New cocoa fermenting box boosts farmers' incomes
In Kasawo, a locally made single cocoa fermenting box improves bean fermentation and helps farmers sell directly to exporters. Researchers report faster, better fermentation, higher prices and plans to scale up production across cocoa districts.