‘Forbidden Symmetry’ Found in 4.5-Billion-Year-Old Meteorite
May 30, 2017
A 4.57 billion-year-old meteorite was found in Russia exhibiting crystals with naturally occurring ‘ forbidden symmetry ‘ for the first time.
Until recently, crystals with forbidden symmetry were thought impossible to naturally occur. Yet, a 4.57 billion-year-old meteorite was found in the far northeastern region of Chukotka, Russia exhibiting crystals with naturally occurring ‘forbidden symmetry‘ for the first time. Dr. Paul Steinhardt from Princeton University led a research team to characterize the nature and occurrence of this enigmatic quasicrystal.
The unorthodox arrangement of atoms, coined forbidden symmetry, had previously been replicated in laboratory experiments and was thought to be too energetically unstable to occur in the natural environment. However, a quasicrystal has been found within the aforementioned meteorite, the second one ever to be found and both within the same meteorite.
What is Forbidden Symmetry?
A quasicrystal is akin to a crystal structure of a mineral, which is ordered, but not periodic like that of a normal crystal. For example if you were to lay 4-sided or 6-sided tiles along the floor, they will neatly fit within one another. However, if you were to do the same with a five-sided or 10-sided tile, there would be resulting gaps in the tile floor, requiring different size/shape tiles to fully fill in the floor. This is a representation of the ordered but not periodic nature of quasicrystals with forbidden symmetry.
The above image depicts a procession around the 10-fold symmetry axis (b) and similar precession perpendicular to the axis (c, d).
This quasicrystal exhibits 10-fold symmetry where disks of 10-sided atomic structures are stacked in a column. The quasicrystal is made up of a unique combination of nickel, iron, and aluminum, a combination not often seen due to aluminum’s preponderance to bind with free oxygen and to block nickel and iron. The first natural quasicrystal, found within the same meteorite but a different grain, exhibited a 5-sided symmetry similar to the pattern seen on a soccer ball.
Still unclear of the Creation
At this point it’s unclear how the quasicrystals exhibiting forbidden symmetry were created. During impact, the host meteorite would have been witness to temperatures up to 1,000 degrees Celsius and pressures as high as 100,000 times that of normal atmospheric pressure. It’s unclear whether the forbidden symmetry found in this meteorite is extraordinary or commonly found within our solar system. In addition, understanding how these crystal structures form will provide clues to new and unique methods in which nature can build crystals under extreme circumstances.
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