Photo: Keck Institute for Space Studies/Chuck Carter
Uranus and Neptune are technically giant planets, but they are commonly referred to as ice giants because of their composition. Compared with Jupiter and Saturn, they contain higher amounts of methane, water, and other volatile substances. Under the extreme pressures inside these planets, such materials are believed to solidify, forming so-called planetary “ices.”
However, scientists from the PlanetS research center at the University of Zurich (UZH) and the Swiss National Centre of Competence in Research (NCCR) have presented new findings that challenge the traditional view of the internal structure of Uranus and Neptune. According to the researchers, these planets may be more rocky and less “icy” than previously assumed, reports Science Alert.
In addition, the study suggests that convection may occur inside these planets, meaning that material circulates rather than remaining stable and stratified. This process—somewhat analogous to convection driven by tectonic activity on Earth—could help explain several unusual features of the ice giants.
Traditionally, scientists have divided the planets of the Solar System into three categories based on composition, which broadly corresponds to their distance from the Sun. These include the rocky inner planets—Mercury, Venus, Earth, and Mars—and the planets beyond the so-called “frost line,” where volatile substances such as water can freeze. Beyond this line are the gas giants (Jupiter and Saturn) and the ice giants (Uranus and Neptune). The new research, however, calls this classification into question.
In their study, the researchers modeled the interiors of Uranus and Neptune using randomly generated density profiles and then calculated the resulting gravitational fields. This process was repeated until the models matched observational data for both planets.
The results indicate that the internal composition of Uranus and Neptune is not limited to ice-rich material and may instead consist predominantly of rocky matter.
These conclusions are consistent with data from the Hubble Space Telescope and NASA’s New Horizons mission, which suggest that Pluto is composed of roughly 70 percent rock and metal and about 30 percent water by mass.
