Iron Experiments May Help Scientists Learn More About the Properties of Earth and Other Planets

Iron is the most stable and heavy chemical element generated by nucleosynthesis in stars, which automatically means it is the most plentiful heavy element in the Universe and in Earth’s core, as well as in the nucleus of other rocky planets 

To better understand the high-pressure of iron, a physicist from Lawrence Livermore National Laboratory (LLNL), together with international collaborators, has discovered the subnanosecond phase transitions in laser-disturbed iron. The study was published in the June 5th, 2020 edition of the journal Science Advances.  

The research could help experts learn more about the physics, chemistry, and the magnetic characteristics of Earth and other planets by calculating time-resolved high-resolution X-ray diffractions for the whole duration of shock compression.  

This enables observation of the timing of the start of elastic compression at 250 picoseconds and the infrared view of three-wave structures between 300 and 600 picoseconds. The X-ray diffraction unveils that the renowned phase transformation from ambient iron (Fe) to high-pressure Fe takes place in 50 picoseconds.  

Image Concept of Earth’s Core

At ambient settings, metallic iron is stable as a body-centered cubic shape, but as the pressure increases above 13 gigapascals, which is 130,000 times the atmospheric pressure on Earth, iron takes the shape of a nonmagnetic hexagonal close-packed structure. This shift is diffusionless, and researchers can see the ability to exist side by side, of both the ambient and high-pressure phases.  

There are still arguments regarding the locations of the phase limits of iron, as well as the kinetics of this stage transformation. The researchers even found the appearance of new phases after 650 picoseconds with densities alike or even lower to that of the ambient stage.  

“This is the first direct and complete observation of shock wave propagation associated with the crystal structural changes recorded by high-quality time series data,” said LLNL physicist Hyunchae Cynn, a co-author of the paper.  

Further experiments may help scientists better understand the way rocky planets took form or whether they have a magma ocean in their core. 

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