The core of the planet is located thousands of kilometers below the surface of Earth, where it can be found under severe pressures and scorching heat. The inner core is composed of a ball of nickel, iron, and other metals. It super-rotates inside the outer core where iron and nickel remain fluid.
A team of scientists led by Sebastien Merkel, physicist at the University of Lille in France, has recreated the conditions of the outer core in a laboratory. Scientists have been able observe the iron's structural deformation.
This has implications for our planet's understanding, and can also help us understand the effects of iron fragments colliding in space.
Arianna Gleason, physicist at the US Department of Energy's SLAC National Accelerator Laboratory, stated that "We didn’t quite make inner core circumstances." "But, we achieved the conditions for the outer core planet, which is truly remarkable."
Normal Earth conditions will result in a cubic lattice crystal structure for iron. The atoms are organized in a grid with one atom at each corner and one at their center. This lattice transforms into a hexagonal structure when iron is compressed at high pressures. This allows for more atoms in the same space.
It's difficult to predict what will happen at higher temperatures and pressures, such as those found in the Earth's core. Laser technology has improved to the point that small samples can now be exposed to extreme conditions in laboratories. This is similar to what's found in white dwarf star pressures and temperatures.
Two lasers were used by the SLAC team. The first laser was an optical laser that was fired at a microscopic piece of iron and subjected it to intense heat and pressure.
The pressures in Earth's outer core range from 135 to 330 Gigapascals (1.3 million to 3.3million atmospheres) and temperatures between 4,000 to 5,000 Kelvin (3.727 to 4.727 degrees Celsius or 6,740-8.540 degrees Fahrenheit). The temperature at 4,070 Kelvin and pressure on the sample reached up to 187 Gigapascals.
The next and most difficult part of this project was to determine the atomic structure for the iron. The team used SLAC’s Linac Coherent Light Source, (LCLS), X-ray-free-eletron laser to probe the sample while the laser fired.
Gleason stated that they were able "to make a measurement within a billionthof a second." "It's really thrilling to freeze the atoms exactly where they are in that nanosecond.
These images were compiled into a sequence and revealed that iron reacts to additional stress by twinning. This happens when the crystal lattice is so compressed that certain points of the lattice are shared by multiple crystals in an symmetrical fashion.
(S. Merkel/University of Lille France)
This means that iron found at outer terrestrial core conditions will have its atomic arrangement pushed to the point that the hexagonal shapes turn by almost 90 degrees. Researchers explained that this mechanism allows the metal to withstand extreme temperatures.
Gleason stated that "twinning allows iron to become incredibly strong – stronger than we initially thought - before its plasticity starts flowing on much longer timescales."
This information can now be used to create models and simulations of iron's behavior under these conditions. This information has important implications for how we understand space collisions. The core of Earth is neatly hidden within a planet. However, there are high-magnetic asteroids which we believe are the naked cores of planets that were formed after their formation was disrupted.
These objects may collide with other objects, which can cause damage to the iron's structure. We now have a better understanding of how this happens. We also know more about our planet.
Gleason stated, "The future looks bright now that we have a way of making these measurements."
"Now, we can give a thumbs-up or thumbs down to some of the fundamental deformation mechanisms physics models." This helps us to improve our predictive ability for modeling how materials react under extreme conditions.
The research was published in Physical Review Letters.
