(ORDO NEWS) — When a space rock passes through Earth’s atmosphere and falls to the surface, it generates shock waves that can cause minerals in the planet’s crust to compress and transform.
Since these changes depend on the pressure developed during the collision, experts can use knowledge of the structure of terrestrial minerals to study the history of meteorites, from the moment of impact to the initial conditions for the formation of these stones in space.
“If you compare an ordinary mineral with a meteorite-impacted mineral, the latter has unique features,” said Arianna Gleason, a scientist at the US Department of Energy’s SLAC National Accelerator Laboratory.
“On the outside, they partially retain their original crystalline form, but on the inside, they become disordered and show amazing intersecting linear structures called lamellae.”
Plagioclase, the most common mineral in the earth’s crust, is one of the most convenient minerals for obtaining information about meteorite falls. However, the pressure at which this mineral loses its crystalline form and becomes disordered – as well as the features of this process, called amorphization – are still the subject of discussion.
In a new experiment, scientists from the SLAC lab performed physical simulations of meteorite impacts to understand the behavior of plagioclase under shock waves.
As a result of the experiments carried out, it was possible to find out that amorphization begins at lower pressures than previously thought.
Also, experiments have shown that after removal of the impact, the material partially crystallizes back with the restoration of its shape, thus demonstrating the memory effect, which can potentially be used in materials technology.
These results may help refine models that provide information about meteorite impacts, including determining the speed of meteorites and the pressure they develop as they fall to Earth.
To conduct their experiments, Gleason and her colleagues used the Matter in Extreme Conditions (MEC) instrument of the Linac Coherent Light Source (LCLS) X-ray laser from the SLAC laboratory.
First, the researchers exposed a sample of plagioclase to a powerful optical laser to send a shock wave through it.
As the shock wave propagated through the sample, the researchers irradiated it with ultrafast pulses of the LCLS X-ray laser at various times. Some of these X-rays were then scattered by the detector and formed a diffraction pattern.
“Just as each person has a unique set of fingerprints, the atomic structure of each mineral is unique,” says Gleason. “The diffraction pattern reveals these ‘fingerprints’, allowing us to track changes in the structure of the atoms in the sample in response to the pressure caused by the shock wave.”
The researchers could also tune the optical laser to different energies to see how the diffraction pattern would change at different pressures.
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