Research finds cause of lost magnetism at meteorite site

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A scientist at the University of Alaska Fairbanks has found a way to locate meteorite impact sites that have long lost their craters.

New Delhi: A scientist at the University of Alaska Fairbanks has found a way to locate meteorite impact sites that have long lost their craters. This discovery could go further in the research of not only Earth’s geology but also other planets in our solar system.


The findings of this study have been published in the ‘Journal of Scientific Reports’. According to work by Günther Klitschka, associate research professor at the UAF Geophysical Institute, the natural remnants of rock hold the key in the very low levels of magnetization that have been subjected to intense forces from meteors and then strike the surface.


Rocks degraded by man-made or non-Earth forces have a natural remnant magnetization of 2% to 3%, meaning they contain trace amounts of magnetic mineral grains – usually magnetite or hematite or both.


Kletetschka found that samples collected at the Santa Fe Impact Structure in New Mexico had less than 0.1% magnetism.


Kletetschka determined that the changes in the behavior of electrons in the plasma and rock atoms formed at the moment of impact are due to minimal magnetism.


The Santa Fe Impact Structure was discovered in 2005 and is estimated to be about 1.2 billion years old. The site consists of easily recognizable shatter cones, which are rocks with fanciful features and radiating fracture lines. Shatter cones are believed to only form when a rock is subjected to a high-pressure, high-velocity shock wave such as a meteor or nuclear explosion.


Kletetschka’s work allowed researchers to determine an impact site prior to the discovery of the shatter cone and to better define the extent of known impact sites that lost their craters due to erosion.


“When you make an impact, it happens at a tremendous velocity,” Keletska said.


“And as soon as there is contact with that velocity, the kinetic energy turns into heat and vapor and plasma. Many people understand that there is heat, maybe there is some melting and evaporation, but people don’t think about plasma, ” They said.


Plasma is a gas in which atoms have been broken down into free-floating negative electrons and positive ions.


“We were able to detect in the rocks that a plasma was created during the impact,” he said.


Earth’s magnetic field lines penetrated everything on the planet. Magnetic stability in rocks can be temporarily knocked out by a shock wave, as they would when hitting an object with a hammer, for example. The magnetic stability in the rocks returns soon after the shock wave has passed.


In Santa Fe, the meteorite impact sent a large shock wave through the rocks, as expected. Kletetschka found that the shock wave changed the characteristics of the atoms in rocks by modifying the orbits of some electrons, leading to the loss of their magnetism.


Modification of the atoms would allow quicker remagnetization of the rocks, but Keletska also found that meteorite impacts had weakened the magnetic field in the region. Despite having the ability to do so, there was no way for the rocks to regain their 2 percent to 3 percent magnetism.


This effect is due to the presence of plasma at the surface and in the rocks below. The presence of plasma increased the electrical conductivity of the rocks as they converted into vapor and molten rock at the leading edge of the shock wave, temporarily weakening the ambient magnetic field.


“This plasma will overcome the magnetic field, and so the rock gets only a very small field, a remnant,” Kletetschka said. (ANI)

First published:November 24, 2021, 2:14 pm

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