When you think of magnets, you probably imagine a boring third-class science experiment, or the tacky palm tree souvenir you picked up on your last beach vacation that now serves to hold up the back electricity bill on the fridge.
Yet magnetism is one of the most defining properties of our planet, allowing us to explain and understand phenomena, from anomalies in the human body to why Santa Claus supposedly lives in the North Pole.
Giant, old magnets might also help us figure out climate change.
New research published in the journal Proceedings of the National Academy of Sciences reveals how giant magnetic fossils from 34-56 million years ago could help scientists understand periods of significant environmental change – both past and present.
Some background – Scientists studied both conventional and huge needle-shaped “magnetofossils” found on the continental shelf in Wilson Lake, New Jersey.
As the study states:
The New Jersey Continental Shelf experienced an overall rapid inflow of clay, mineralization of iron oxides, dinoflagellate bloom, and benthic foraminifera turnover.
As a result, these fossils contain the remains of microscopic, magnetotactic bacteria and other microorganisms with iron components. In the case of these bacteria, magnetotactic means that they orient themselves along magnetic field lines.
As the study explains, the bacteria in magnetofossils formed magnetic chains, which acted like a small-scale compass. This magnetic power guided the microorganisms to beneficial nutrients in nearby oceans using Earth’s magnetic field as a roadmap to food.
Ancient giant magnetofossils, formed some 34-56 million years ago, took these magnetic properties to another level and formed unique shapes, including “ giant balls, spindles, and needles, ” which were about 20 times the size of conventional magnetic fossils , according to the investigation.
How they did it – Unlike previous studies, where samples of magnetofossils were ground into powder, these researchers examined the fossils without damaging them.
The scientists came up with a new high-resolution technology to analyze magnetofossils, known as first-order reversal curves (FORC).
According to the study, FORC can “measure the response of all magnetic particles, including giant magnetofossils, in a bulk sample of sediment.”
They also used transmission electron microscopy to generate an image of the samples using an electron beam. Finally, they used simulations to predict the magnetic behavior of giant needles in the fossils.
Sample retention is important for future research, Courtney Wagner, lead author of the study and a PhD student from the University of Utah, said in a press statement.
“The extraction process can be time-consuming and unsuccessful, electron microscopy can be costly, and the destruction of samples means they are no longer useful for most other experiments,” Wagner says.
What’s new – The giant, needle-shaped magnetofossils – similar to the needle of a compass – produce “different magnetic signatures” from those typically found in conventional magnetic fossils, the researchers found.
These different features could eventually reveal other giant magnetofossils, according to the study.
The structure of conventional magnetofossils is “optimized for magnetic navigation,” because they “generate the maximum magnetic moment with a minimal amount of iron,” the study said.
Curiously, the structure of giant magnetofossils is more variable than the researchers expected. One theory they present is that these giant magnetofossils may have formed during a time when iron was abundant, making efficient magnetic movements less critical to the organisms’ survival.
Why it matters – The giant needle magnet fossils are uniquely associated with periods of ancient environmental problems.
In turn, researchers could use these fossils to better understand how ecological disturbances affect ancient marine life and the ocean ecosystem.
“It’s so nice to be part of a discovery like this, something that can be used by other researchers studying magnetofossils and intervals of planetary change,” Wagner says.
“This work can be used by many other scientists, within and outside our specialized community. This is very exciting and rewarding,” she adds.
There are no living things forming giant magnetofossils, making the study of these specimens incredibly important.
Ultimately, they could act as a time capsule, revealing ancient changes in the geological record – and hidden insights into contemporary climate change and the world’s oceans.
According to the study:
By studying the occurrence of giant magnetofossils, we can better understand how sensitive marine ecosystems responded to past events due to climate change.
If the microorganisms in these fossils could use magnetic fields to respond to and adapt to past climate change, using Earth’s magnetic field to find nutrients for survival, those lessons might help us. help to respond and adapt to the climate crisis of the present.
What’s next – “The organisms that produced these giant magnetofossils are utterly mysterious, but this leaves exciting avenues of research open for the future,” said Ioan Lascu, a study co-author and researcher at the Smithsonian National Museum of Natural History, in the statement. .
But the scientists need to do more research to fully understand the composition of the magnetic bacteria in these giant fossils.
“Collecting and storing these samples requires specialized personnel, equipment and planning, so we want to preserve as much material as possible for additional studies,” Wagner says.
Summary: Coastal marine sediments deposited during the Paleocene-Eocene Thermal Maximum in Wilson Lake, NJ contain abundant conventional and giant magnetofossils. We find that giant needle-shaped magnetofossils from Wilson Lake produce different magnetic signatures in low-noise, high-resolution first-order reversal curve (FORC) measurements. These magnetic measurements on bulk sediment samples identify the presence of giant needle-shaped magnetofossils. Our results are supported by micromagnetic simulations of giant needle morphologies measured from transmission electron microscope images of magnetic extracts from Wilson Lake sediments. These simulations underscore the single domain characteristics and the high magnetic coercivity associated with the extreme crystal elongation of giant needles. Giant magnetofossils have so far only been identified in sediments deposited during global hyperthermic events and can therefore serve as magnetic biomarkers for environmental disturbances. Our results show that FORC measurements are a non-destructive method of identifying giant magnetofossil assemblies in bulk sediments, which will help test their ecology and significance with regard to environmental changes.