We already knew that meteorites can store valuable information on their structure and composition. However, now we have discovered a problem: that this information is more sensitive than we thought. So much so that the same tools that are used to search for them can harm it.
A troublesome tool. A study has just analyzed how simple magnets can affect the magnetic fields of rocks that come to us from space, meteorites. Magnets are very often used by meteorite hunters, especially amateurs, to identify this type of rock.
New technologies and our ever-widening knowledge of the history of our planet and our solar system have led many geologists to begin studying meteorite magnetic fields to better understand our environment.
Many will not. Since these fields will have been damaged in the previous search and identification process.
A flagrant case. Black Beauty is the name by which a meteorite found in 2011 in Western Sahara is known. The authors use this rock as an example of the damage that magnets can cause to subsequent research.
Black Beauty is a rock whose crystals formed 4.4 billion years ago on Mars. This implies that it is older than any other rock originating from our own planet. The rock must have contained important information about the magnetic field of Mars, which we believe disappeared about 4 billion years ago.
But when the European paleomagnetist Jerome Garracceca tried to analyze the rock’s magnetic field, he realized that it had been altered. “It’s a shame that, just by using magnets, we have been destroying this scientific information stored there for 4,000 million years,” Garracceca said for Science.
An earthly experiment. Now a French-American team of researchers has studied how and to what degree magnets can affect the magnetic fields of meteorites that experts find. For this they did not have to manipulate and damage any meteorite since they used basaltic rocks of terrestrial origin.
Thanks to them, they were able to measure the effect of magnets on the magnetic fields of the rocks and how the latter reset when they came into contact with the former. They also found that the effect was gradual, from the outside in, so they were able to calculate how far into the sample geologists could cut off “pure” fractions of the rocks’ original magnetic field.
The team has published the details of their research in an article in the Journal of Geophysical Research: Planets.
Losses for the scientific community. “It’s like having this unique piece [de información] destroyed” also explained to Science Foteini Vervelidou, one of the authors of the work. “Why would you buy a wonderful painting and then throw sauce on it?” Even the US Geological Survey recommends the use of magnets as a way of detecting and identifying meteorites.
This despite being far from being an infallible system. Magnets, the authors note, are good at identifying chondrites, a relatively abundant type of meteorite. However, they can generate false positives when faced with rocks such as basalt, rich in iron. In addition, they fail to detect many meteorites.
The authors also offer an alternative to meteorite finders. Magnetic susceptibility meters. The magnetic fields used by these devices are weak enough not to affect those of meteorites and therefore do not erase the information in them. In addition, they explain, they are more precise in their ability to identify this type of rock of extraterrestrial origin.
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Image | POT
