Scientists ask meteorite hunters to stop using magnets to test finds
Scientists are asking meteorite hunters to refrain from using magnets to test the authenticity of their finds because this can destroy the specimen's magnetic memory, erasing valuable information about the nature of the solar system.
Once dismissed as superstition, meteorites are now big business with some cosmic fragments selling for thousands of dollars and a few for well over a million. However, just as valuable is the knowledge that they've brought us about the early days of the solar system and how it formed.
We now know that almost all of the tens of thousands of meteorites that have been found originated from about 100 parent bodies in the solar system. We also know that some of these meteors were hurled into space from other planets, most notably Mars.
About 175 Martian meteorites have been found to date, with most coming from North Africa and Antarctica, where they stand out against the lightly colored, barren landscape. From these, scientists can learn a great deal about the Red Planet.
But a new Massachusetts Institute of Technology (MIT) study has shown that collectors, dealers, hunters, and museum curators have inadvertently destroyed valuable evidence by testing meteorites with magnets.
Since most meteorites are composed of nickel and iron, a cheap magnet is a simple way to test a suspected specimen. Touch the magnet to it and if it sticks, then that's a positive.
But when a rock containing magnetic materials first forms or cools down after being heated to high temperatures, it will pick up the local magnetic field. By analyzing this signature, scientists can deduce all sorts of things, including the strength of the original field and the age of the sample.
The MIT study looked at a famous meteorite called Northwest Africa (NWA) 7034 or Black Beauty, which was found in 2011 in the Sahara Desert. Multiple shards of this obsidian-black meteorite have been found all over northeast Africa and scientists estimate that it is 4.4 billion years old, which makes it very interesting because it dates back to a time when Mars had water and a magnetic field.
However, what the team found was that many shards from Black Beauty had been re-magnetized on Earth and their ancient Martian magnetic field was erased. This not only destroyed valuable information, it also introduced misleading false data that can lead to scientific dead ends.
As part of the new study, the team developed a mathematical model based on looking at the field of an ordinary hand magnet, how it can alter the magnetic properties of terrestrial minerals, and determining how well this fits the model against experiments. This allowed the team to determine whether a sample had been re-magnetized and how deep inside the specimen the re-magnetizing penetrates.
The team is asking meteorite hunters to avoid using magnets and to instead use susceptibility meters, which can identify a meteorite by measuring a sample's susceptibility to magnetism without erasing its field. Unfortunately, such meters cost thousands of dollars, so some testing may have to be done further up the line from meteorite hunters, such as by collectors and museums.
"There’s been this incredible explosion of meteorite diversity and number in the last 20 years or so, and we owe meteorite hunters a thanks for finding these things," said Benjamin Weiss, professor of planetary sciences at MIT. "But the trade-off, the devil’s bargain, is that often they are using magnets to find them, and are immediately destroying their magnetic record in the process."
The research was published in the Journal of Geophysical Research: Planets.
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How can the magnetism in a piece of space rock tell us anything meaningful? Does it have some kind of a pattern to it like a sound recording that can be played back over and over again? How is any data bout the nature of the solar system recorded in a piece of space rock?
The "Big Bang" theory has been disproved since about 1970, when after a 20 year long study of the spectral lines of many thousands of stars all over the galaxy, the astronomer couldn't find even just two that were anywhere near being similar, let alone the same!! Each star's light output is unique, which wouldn't be so, if they all came from the same origin point at the same time! And if there actually was some kind of origin point of every bit of matter in the universe, how did it come about? Where did it come from? Why did it suddenly explode? What was it that lit that Cosmic Fuse, if that is what really happened? And recently, the JWST was used to make a discovery which further proved the BBT to be a crock of smelly stuff!!
Should a metal detector be used instead? Finding small parts is difficult and just a visual observation is often not enough.
A meteorite of at least a few kilograms in size can survive passing through the atmosphere. The outer crust will get quite hot but rocks are poor conductors of heat so the interiors remain cold so they would retain any inherent magnetic information.
A small meteorite that formed in space as a small object might not have any interesting magnetic information as it would tumble while cooling. That is just my guess.
However, it is thought that many meteorites come from small planetoids that formed then broke apart. These cooled very slowly (degrees Kelvin per million years) and their spin would presumably maintain a fixed orientation so I suspect these could have useful information.