Don’t bother with a compass (Image: JPL/NASA)

WHAT glows yellow and behaves like a liquid and a solid at the same time? Water – at least in the strange form it appears to take deep within Uranus and Neptune. This exotic stuff might help explain why both planets have bizarre magnetic fields.

Simulations in 1999 and an experiment in 2005 hinted that water might behave like both a solid and a liquid at very high pressures and temperatures. Under such conditions, the oxygen and hydrogen atoms in the water molecules would become ionised, with the oxygen ions forming a lattice-like …