Scientists ask meteorite hunters to avoid using magnets to confirm the authenticity of their finds, as this could destroy valuable information about the nature of the solar system, for example, by destroying its magnetic memory. Once dismissed as superstition, meteorites are now big business, with some of the space debris sold for thousands of dollars and some for a million. However, the information they bring to us about the early days of the solar system and how it formed is just as valuable.

We now know that almost all of the tens of thousands of meteorites found come from about 100 major bodies in the Solar System. We also know that some of these meteorites were launched into space from other planets, especially Mars.

To date, about 175 Martian meteorites have been found, most from North Africa and Antarctica, where they stand out against the bright, barren landscape. Scientists can learn a lot about the Red Planet from them. But a new study by the Massachusetts Institute of Technology (MIT) has revealed that collectors, traders, hunters and museum curators inadvertently destroy valuable evidence when examining meteorites with magnets.

Since most meteorites are made of nickel and iron, an inexpensive magnet is an easy way to test a suspicious sample. Touch it with a magnet and it’s positive if it sticks. But when a rock containing magnetic materials first forms or cools after being heated to high temperatures, it will pick up the local magnetic field. By analyzing this signature, scientists can understand all sorts of things, including the strength of the source field and the age of the example.

The MIT study looked at a famous meteorite called North West Africa (NWA) 7034, or Black Beauty, found in the Sahara desert in 2011. Several fragments of this obsidian black meteorite have been found in northeast Africa, and scientists estimate 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, the team discovered that many pieces of Black Beauty were re-magnetized on Earth and the old Martian magnetic fields were erased. This not only destroyed valuable information, but also revealed misleading false data that could lead to scientific deadlocks.

As part of the new work, the team developed a mathematical model based on determining the field of an ordinary hand magnet, how Earth’s minerals can change their magnetic properties, and how well the model matches the experiments. This allowed the team to determine if the sample was remagnetized and how deeply the remagnetization had penetrated the sample.

The team asks meteorite hunters to avoid using magnets and instead use susceptibility meters that can identify a meteorite by measuring the sample’s susceptibility to magnetism without erasing its field. Unfortunately, such meters cost thousands of dollars, so some researchers may need to do more testing than meteorite hunters like collectors and museums.

“There has been an incredible explosion in the diversity and number of meteorites over the last 20 years, and we have to thank meteorite hunters for finding them,” said Benjamin Weiss, professor of planetary sciences at MIT. “But the compromise is that the devil’s deal is that they usually use magnets to find them and immediately destroy their magnetic record.”