High Power Laser Assists Scientists in Discovering a New Stage of High Density and Ultra High Temperature Ice

As is well known, the outer planets of our solar system, Uranus and Neptune, are gas giants rich in water. The extreme pressure on these planets is 2 million times that of the Earth's atmosphere. Their interiors are also as hot as the surface of the sun. Under these conditions, water exhibits a strange high-density ice phase.

Researchers have recently observed one of the stages, called Ice XIX, which is the first to use high-power lasers to reproduce necessary extreme conditions. The Neptune model shows the potential depth of the newly discovered body centered cubic superion ice XIX. It can explain Neptune's multipolar magnetic field (purple), which is due to an increase in conductivity and tilt relative to the axis of rotation (green).

Image source: SLAC National Accelerator Laboratory
Researchers measured the Ice XIX structure under extreme conditions using a linear accelerator coherent light source (a groundbreaking X-ray laser device) and found that oxygen atoms are arranged in a body centered cubic structure, while hydrogen atoms move freely like fluids, greatly improving conductivity. Their paper is published in the Science Report.

Voyager 2 is a solar system exploration spacecraft launched by NASA in 1977, which measured the extremely unusual magnetic field around Uranus and Neptune. Scientists believe that the strange states of so-called superionic ice are a possible explanation, as the conductivity of these states increases. This work proves the existence of the previously undiscovered Ice XIX phase. It indicates that the phase can be formed at the correct depth and helps to interpret the Voyager 2 magnetic data.

Water is a common compound in the solar system and essential for life. It exhibits an exceptionally complex pressure temperature phase diagram, with 18 crystalline ice phases identified. There is no more important dense ice phase than the interior of gas giants such as Uranus and Neptune. Scientists speculate that the complex magnetic fields of these planets are generated by the strange high-pressure state of water ice with superionic properties. However, under these extreme conditions, the structure of ice is difficult to measure.

Researchers have found the first direct evidence for the use of extreme condition instruments using linear accelerator coherent light sources, ultra fast X-ray free electron lasers, and Department of Energy (DOE) science office user facilities to detect the new stage of high-density ultra-hot water ice in laser driven dynamic compression processes.

At 200GPa (2 million atmospheres) and 5000K (8500 ° F), this new high-pressure ice phase (known as Ice XIX) has a body centered cubic (BCC) lattice structure. Although other structures are theoretically stable under these conditions, the BCC structure of Ice XIX will increase the conductivity inside the ice giant much deeper than previously thought.

These results provide an important and convincing origin for the multipolar magnetic fields measured by the Voyager 2 spacecraft on Uranus and Neptune.

Source: Ofweek