Icy planets, such as Uranus (U) and Neptune (N), are found in both our solar system and other solar systems across the universe. Nonetheless, these planets, characterized by a thick atmosphere and a mantle made of volatile materials (e.g., hydrogen water, ammonia, etc.), are the least explored class of planets; thus so far little is known about their origin, interior structure and composition.
The Voyager probes, two robotic systems launched by NASA on a quest to explore the outer solar system, recorded interesting measurements suggesting that icy planets have peculiar magnetic fields. These measurements showed that unlike other types of planets, such as terrestrial planets and gas giants, icy planets do not have a dipolar magnetic field, and are thus without clear North and South magnetic poles.
Researchers at Ecole Polytechnique, Sorbonne Université and other institutes in Europe recently carried out a study aimed at better understanding under which form matter could exist inside these widely unexplored planets. Their paper, published in Nature Physics, specifically reports the melting curve of superionic ammonia in conditions similar to those that astrophysics expect to find inside U and N.
“The atmospheric composition of U and N suggests their mantle are made of a complex mixture of C, H, N and O atoms, which could also be expressed in a mixture of water (H2O), ammonia (NH3) and methane (CH4), the so-called ‘planetary ices’,” Jean Alexis Hernandez, one of the researchers who carried out the study, told Phys.org.
“However, the lack of thermodynamic data on these compounds and their mixtures at the extreme conditions (several millions of times the Earth atmospheric pressure and several thousands of Kelvin) of U and N impedes current geophysical models of these planets. Most current models consider that the mantles are made of pure water and the effect of other compounds is still unknown.”
2023-07-11 16:48:03
Article from phys.org