Uranus and Neptune are called ice giants because they are thought to be made up mostly of icy materials like water, methane, and ammonia, surrounding a hot, rocky core.
Scientists think this because these planets formed in an area that likely had a lot of these components, making them rich in these icy materials.
Early Theories
Early models of Uranus and Neptune were based on the idea that they formed in the outer parts of a young solar system.
These models assumed the planets would have similar elements to the Sun, known as solar elemental abundances.
Scientists used these assumptions to predict what the planets might be made of, expecting a mix of ices and rocks.
Limited Exploration
NASA hasn’t spent much time studying Uranus.
The only spacecraft to visit was Voyager 2, which also visited Neptune and provided better observations than telescopes on Earth can.
These observations matched the early models, suggesting the models were correct.
Voyager 2’s flybys provided the best data we have, but it’s still quite limited.
A Mystery Remains
However, there’s still a mystery.
Objects in the Kuiper belt, which is beyond Neptune, have a lot of organic materials but not much water, indicating that the planets might have more rocky materials.
This suggests Uranus and Neptune should have more rock than ice. So why do the early models seem to fit? This contradiction has puzzled scientists.
New Findings
Scientists created hundreds of thousands of new models of Uranus and Neptune, changing the chemical compositions until they found ones that matched the planets’ mass and structure.
They discovered that the best-fitting models had interiors with at least 10% methane, and in some cases, methane was more abundant than water.
This was a surprising result, as it suggested a different composition than previously thought.
How Did Methane Get There?
The team suggests that as Uranus was forming, carbon-rich objects collided with the planet.
These collisions, under intense heat and pressure, caused chemical reactions that produced a thick layer of methane.
This would mean that during the planet’s growth, carbon from these objects reacted with hydrogen to create methane.
What’s Next?
To confirm these findings, we need more detailed observations of Uranus and Neptune.
In short, we need to take a closer look at Uranus to understand its composition better.
This could involve sending new missions to Uranus to gather more data and refine our models.