The site of a meteorite impact may seem easy to spot, as the giant craters on the Earth’s surface indicate where these distant hard bodies finally stopped. But it’s not always like this.
Sometimes trauma scars heal, are hidden by layers of soil and vegetation, or are resurfaced by the elements over a long period of time. Scientists have now found a way to find these hidden impact sites.
Think of a large piece of space rock approaching its final destination on Earth. Meteorites can enter Earth’s atmosphere At 72 kilometers per second (160,000 miles per hour), it begins to slow down as it moves through our relatively dense atmosphere.
Beautiful light in the sky when meteors fly in the sky becauseeradicationWhere layers and layers of meteorites evaporate through high-speed collisions with air molecules.
Then, if the space rock reaches Earth, it collides with Earth, forming crushing cones, Impact craters, and other signs of a meteorite impact here.
This is an intense geological process, with high temperatures, high pressures, and fast particle velocities, all synchronized. One of the things that happens during this intense process is the effect it forms in plasma – a type of gas in which atoms are split into electrons and positive ions.
“When you have an impact, it’s very fast,” He said Geologist Gunter Klitschka from the University of Alaska Fairbanks.
“Once there is contact at that velocity, there is a change in kinetic energy into heat, vapor and plasma. A lot of people notice there’s heat, maybe something melts and evaporates, but people don’t think about plasma.”
What the team found here was that all of that plasma did something odd to the rock’s natural magnetism, leaving an impact zone where the magnetic force was about 10 times lower than normal normal magnetic levels.
residual natural magnetization This is the amount of natural magnetism present in rocks or other sediments.
When the earth’s sediments gradually settle after being laid, those small sediments Magnetic metal grain inside They line up along the planet’s magnetic field lines. These grains then remain trapped in their direction within the hard rock.
That’s a very small amount of magnetization – about 1-2 percent of the rock’s saturation level, and you can’t tell the difference from a regular magnet, but it sure does exist, and it can. It can be easily measured with geological equipment.
However, when a shock wave occurs – as in a meteor impact – there is a loss of magnetism, as the magnetic grains get a good burst of energy.
“Shock waves provide energy in excess of the energy (>1 GPa for magnetite >50 GPa for hematite) required to block magnetic residues within individual magnetic grains,” The researchers write in a new study.
Usually the shock wave passes and the rock returns to its original magnetism level immediately. But as the 1.2 billion year old team discovered Santa Fe Effect Structure In New Mexico, magnetism has not returned to its normal state.
Instead – they suggest – the plasma creates a “magnetic shield” that keeps the grains in a solid state, and just randomly orients themselves. This causes the magnetic density to drop to 0.1 percent of the rock’s saturation level – a 10-fold decrease from the normal level.
“We provide support for a newly proposed mechanism by which the appearance of a shock wave can generate a magnetic shield that allows the magnetic grains to be maintained in a supermagnetic-like state immediately upon exposure, leaving the individual magnetic grains in random directions, dramatically reducing the overall magnetic field. magnetic density, The writing team.
“Our data not only show how the collision process enables a reduction in the intensity of the magnetic dimmer, but also inspires a new direction of effort to study the impact site, using the reduction in the intensity of the dimmer as a new impact indicator.”
Hopefully, this new discovery means that scientists have other tools in their belt when it comes to finding impact sites, even those without natural signs of impact, such as broken cones or craters.
Search published in Scientific Report.
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