Why you shouldn’t use magnets when looking for meteorites
It’s time to drop the magnets, meteorite hunters. The generally used methodology for figuring out area rocks can destroy scientific data.
Touching even a small magnet to a meteorite can erase any report the rock might need retained concerning the magnetic subject of its dad or mum physique, researchers report within the April Journal of Geophysical Analysis: Planets. And the priority isn’t theoretical: a subset of the oldest identified Martian meteorites seem to have already had their magnetic reminiscences wiped, the staff confirmed.
Scientists usually flip to meteorites to get a closeup take a look at different worlds, in addition to perceive our personal. The area rocks can include traces of planetary atmospheres, the chemical constructing blocks for all times and extra (SN: 1/26/21; SN: 4/26/22).
Planetary scientist Foteini Vervelidou makes use of meteorites from Mars — chunks of the planet that had been blasted into area by an influence and later captured by Earth’s gravity — to check its historical previous. Only a few hundred are identified to exist. Rarer nonetheless are specimens that include minerals carrying imprints of the Purple Planet’s magnetic subject, which collapsed about 3.7 billion years in the past (SN: 9/7/15). The oldest identified Martian meteorites, which date to roughly 4.4 billion years in the past, subsequently current an “wonderful likelihood to check the magnetic subject,” says Vervelidou, of MIT and the Institute of Earth Physics of Paris.
However such alternatives will be readily squandered, Vervelidou and colleagues have proven. The staff’s numerical calculations and experiments with earthly rocks — stand-ins for meteorites — confirmed that bringing a hand magnet near a rock can rearrange the spins of the rock’s electrons. That rearrangement overwrites the imprint of a earlier magnetic subject, a course of referred to as remagnetization.
What’s extra, the method seems to occur steadily. The staff examined 9 meteorites discovered at completely different occasions and locations on Earth. All of them are thought to have originated from the identical oldest identified chunk of Mars, which probably broke up when it entered Earth’s environment. All had been remagnetized.
The discovering is unlucky, but it surely’s not stunning, says Melinda Hutson, a meteoriticist at Portland State College in Oregon and the curator of the Cascadia Meteorite Laboratory who was not concerned within the analysis. “Nearly everybody desires to stay a magnet on the aspect of a possible meteorite.”
It’s doable to guage a meteorite with out destroying its magnetic properties. Vervelidou makes use of a lab instrument referred to as a susceptibility meter, which measures how an object would reply to a magnetic subject. And transportable variations exist: She and a staff of meteorite researchers used one to search out almost 1,000 meteorites on a latest expedition in Chile. Hopefully, Vervelidou says, a few of these area rocks will make clear Mars’ magnetic previous.
