For many years, scientists used the term “ice giants” to refer to Uranus and Neptune, believing that their bodies were composed of frozen materials. However, according to new models, there may be molten magma inside them.
Doubts about the “icy” nature of Uranus and Neptune
Despite decades of models, research, and hypotheses, the debate surrounding the long-standing nickname “ice giants” for Uranus and Neptune is heating up again. This is because a study published on the arXiv preprint server and submitted to the Astrophysical Journal may show that this nickname isn’t quite as “frozen” as scientists have long believed. In any case, the work of a team of researchers from the University of California, Los Angeles (UCLA) may lead to the resolution of long-standing scientific disputes.
Uranus and Neptune remain two of the most mysterious objects in the Solar System, mainly because they were visited only by NASA’s Voyager 2 spacecraft in 1986 and 1989, respectively. Their nickname, “ice giants,” stems from long-standing hypotheses that their interiors consist of an icy mantle beneath their atmospheres of hydrogen and helium. Although Jupiter and Saturn are also composed primarily of hydrogen and helium, Uranus and Neptune are believed to have a layered structure consisting of icy components in their interiors.
For their study, the scientists used a series of computer models to simulate and determine the internal composition and processes on Uranus and Neptune. The main motivation for the study was to confirm or refute long-standing models and hypotheses regarding the status of Uranus and Neptune as “ice giant planets.”
Although earlier models suggested that both worlds have an atmosphere of hydrogen and helium covering a vast “ice” mantle composed of water, ammonia, and methane, and a rocky core inside, studies of the magnetic fields and heat distribution on both planets have left scientists at a loss.
New data on the internal structure of “ice” giants
The researchers note that this study may not only shed light on the internal structure of Uranus and Neptune, but can also serve as a model for sub-Neptunian exoplanets. These are the most common type of exoplanets in our galaxy and have radii ranging from 1 to 4.5 times that of Earth. Since there is no such planet in our Solar System, the formation and evolution of these exoplanets remain a mystery.
A new study suggests that the interior of Uranus and Neptune may not be rich in “hot ices” as previously thought, but instead consist mostly of a deep ocean of magma. This is just one possible model for the planets’ internal structure, but it agrees well with existing observations.
The planet’s layers proposed by the study include an atmosphere of hydrogen and helium, which transfers heat to the upper atmosphere and radiates it into space. Below this layer lies an intermediate layer composed of several elements, including hydrogen, helium, magnesium, silicon oxide (SiO), and oxygen. Finally, the lower layer is a magma ocean composed of silicate, iron, and hydrogen.
Connection between “ice giants” and sub-Neptunes
In its conclusions, the study notes: “Although this is just one of several models that successfully reproduce the observed characteristics of Neptune and Uranus, this model has several advantages. One of them is its connection to other gas dwarf planets; it is not entirely obvious that ice giants and sub-Neptunes should differ fundamentally simply because of their distance from their star.”
“Related to this is the fact that the most basic chemical features of the ice giants resemble those of gaseous sub-Neptunes, perhaps indicating similar boundary conditions for the chemistry of the atmospheres imposed by the magma oceans.”
Although Voyager 2 remains the only spacecraft to have visited Uranus and Neptune, and no return missions are currently planned, several mission concepts have been proposed. These include the Uranus Orbiter and Probe (UOP) and Neptune Odyssey, with the UOP using a probe to dive into Uranus’s atmosphere, while both mission concepts enter orbit around the planets and simultaneously study their numerous moons.
According to phys.org
