November 26, 2024
It was a major surprise when the Voyager 2 spacecraft discovered in 1986 and 1989 that the two ice giant planets in our solar system, Uranus and Neptune, do not have the typical dipolar magnetic fields. Instead of having well-defined north and south poles that we know from Earth, Jupiter and Saturn, these magnetic fields are much more disordered. It has remained unexplained for 30+ years what Uranus and Neptune are missing for their magnetic fields to organize themselves into strong dipolar fields. A research article in the Proceedings of the National Academy of Sciences (PNAS) by Burkhard Militzer (professor for planetary science) now offers a really attractive solution for this puzzle:
Phase separation of planetary ices explains nondipolar magnetic fields of Uranus and Neptune.
Prof. Militzer conducted computer simulations of planetary ices (water, methane and ammonia) and was able to show that they phase separate into two fluids (a bit like oil and water) at high pressure. Uranus and Neptune are thus predicted to have two distinct, liquid layers in their interiors: a thin convecting upper layer, rich in water, where the disordered magnetic field is generated and a lower layer composed of carbon, nitrogen and hydrogen that is magnetically inactive.
Phase separation of planetary ices explains nondipolar magnetic fields of Uranus and Neptune.
Prof. Militzer conducted computer simulations of planetary ices (water, methane and ammonia) and was able to show that they phase separate into two fluids (a bit like oil and water) at high pressure. Uranus and Neptune are thus predicted to have two distinct, liquid layers in their interiors: a thin convecting upper layer, rich in water, where the disordered magnetic field is generated and a lower layer composed of carbon, nitrogen and hydrogen that is magnetically inactive.
- The work was reported in the NY Times "Vast Oceans of Water May Be Hiding Within Uranus and Neptune".
- Robert Sanders from Media Relations at UCB wrote "A clue to what lies beneath the bland surfaces of Uranus and Neptune".
- A recording of a research presentation can be found on youtube.