Meteorite impact sites may seem easy to spot, as giant craters in the Earth’s surface show where these distant, violent bodies finally stopped. But it is not always this way.
Sometimes trauma scars are healed, hidden by layers of dirt and vegetation, or worn smooth again by the elements over long periods of time. Scientists have now found a way to discover 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 a meteor flies in the sky because oferadicationWhere the layers and layers of the meteorite evaporate through high-speed collisions with air molecules.
Then, if the space rock reaches Earth, it collides with Earth, forming smashing 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 simultaneous. One of the things that happens during this intense process is that the effect forms a plasma – a type of gas in which atoms are broken down into electrons and positive ions.
“Once there is contact at that speed, there is a change in kinetic energy into heat, vapor and plasma. A lot of people realize there is heat, maybe some melting and evaporation, but people don’t think about plasma.”
What the team found here was that all that plasma did something strange to the rocks’ natural magnetism, leaving an impact zone where the magnetism was about 10 times lower than the normally normal levels of magnetism.
residual natural magnetization It is the amount of natural magnetism present in rocks or other sediments.
When the sediments of the earth gradually settled after being laid down, the small sediments were Magnetic metal grains inside They lined up along the lines of the planet’s magnetic field. These grains then remain trapped in their directions within the hard rock.
That’s a very small amount of magnetization – about 1-2 percent of the rock saturation level, and you can’t tell with an ordinary magnet, but it sure is there, and it can It can be easily measured by geological equipment.
However, when the shock wave occurs – like in a meteor impact – there is a loss of magnetism, as the magnetic grains get a good burst of energy.
“The shock wave provides energy in excess of the energy (>1 GPa for magnetite >50 GPa for hematite) required to prevent 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 level of magnetism almost immediately. But as the 1.2 billion-year-old team found Santa Fe Effect Structure In New Mexico, magnetism has not returned to its normal state.
Instead – they suggest – the plasma created a “magnetic shield” that kept the grains in their crowded state, and the grains were just some sort of random routing. This caused the magnetic density to drop to 0.1 percent of the rock’s saturation level – a 10-fold drop from the normal level.
“We provide support for a newly proposed mechanism whereby the appearance of a shock wave can generate a magnetic shield that allows magnetic grains to be maintained in a supermagnetic-like state shortly after exposure, leaving individual magnetized grains in random directions, dramatically reducing the overall magnetic density,” The team writes.
“Our data not only demonstrates how the impact process allows magnetic dimmer intensity reduction, but also inspires a new direction of effort to study impact sites, using dimmer intensity reduction as a new impact indicator.”
Hopefully, this new discovery means that scientists have another tool in their belt when it comes to finding impact sites, even those that don’t have the natural signs of impact, like smashed cones or craters.
The search was published in Scientific Reports.