According to RT, the observations reveal a solution to a “decade-old mystery” by simulating, in slow motion, what happens to materials exposed to the extraordinary force of an asteroid impact.
The team was able to reveal how the intense pressure causes quartz to form the distinctive layered structure that scientists have long known as a fingerprint of the impact event.
Although they are catastrophic events that melt parts of Earth’s rock and create huge craters, direct evidence of past asteroid impacts can be more subtle than one might expect.
“It is often difficult to detect craters on Earth because erosion, weather and plate tectonics cause them to disappear over millions of years,” explains Professor Langenhorst.
Instead, scientists are looking for signs of impact strength, as preserved by diagnostic changes to some particular minerals in the rock record.
For example, quartz sand, which is essentially just silicon dioxide, gradually turns into glass through impact, with the grains of the mineral intersected by distinct microscopic, layered structures called lamellae.
“For more than 60 years, these lamellar structures have served as an indicator of an asteroid impact, but no one yet knows how this structure formed in the first place. We have now solved this decades-old mystery,” Lerman said.
The key to simulating the impact was to generate pressures of unusual intensity that you would normally see in the Earth’s interior. This is achieved in a lab setting by compressing a sample of material between two diamonds in a piece of equipment known as a diamond anvil cell.
In their study, the researchers used a so-called dynamic diamond anvil cell (DAC), which can not only generate extreme pressures, as prevailing in Earth’s interior or in an asteroid collision, but also change such pressures very quickly.
The team pressed small pieces of single-crystal quartz into this machine, and watched how the pressure affected the structure of the crystals by shining intense X-ray light from the PETRA III synchrotron in Hamburg, Germany. A synchrotron is a type of spin particle accelerator, in which a beam of accelerated particles travels around a loop .
As the name suggests, the magnetic field used to keep the beam on its circular path is synchronized with the particles’ kinetic energy, which also increases with time.
Professor Langenhorst said: “For decades, these plates have been used to detect and analyze asteroid impacts. But only now can we accurately explain and understand their formation.” The full results of the study have been published in the journal Nature Communications.
