Reading in primordial dust
The meteorite “Bishunpur” travelled through space well over 4.6 billion years before it fell to Earth in northern India more than 120 years ago. Now it has turned out that it contains the oldest magnetic recording of our solar system.
A “TITAN” resides in Jülich’s Ernst Ruska-Centre, or more precisely, in room 2010, where a plaintive, clacking sound fills the laboratory whenever the machine sets to work. It comes from a vacuum pump that protects the nano samples from adversities like fine dust because “TITAN 60-300”, a special electron microscope, requires perfect conditions to examine materials right down to individual atoms. Even the smallest of contaminations would falsify the entire result. What makes the TITAN special: it works with an unusual imaging method known as electron holography, which is used by only few research groups worldwide. This allows it to examine not only the atoms but also their magnetisation.
This is where our story begins. We will hear about a meteorite that crashed to Earth decades ago, take a closer look at melted rock samples of the meteorite – and learn something about patience. So what’s the story about? It is about magnetism; more specifically, it is about evidence of how its forces possibly fared 4.6 billion years ago. The focus is on a few crumbs of rock, pieces of the meteorite “Bishunpur”, which fell to Earth in India 123 years ago. Fragments of it are now in the possession of the Natural History Museum in London.
Geophysicist Jay Shah is one of the scientists who, during his PhD at Imperial College London and the Natural History Museum in London, spent months studying the relics. “The rock samples are very different from what we find on Earth,” he says. “Tiny iron grains in the rock have a magnetisation that forms complex, uneven vortex structures.” What is really exciting is that these iron particles consisting of kamacite, an alloy of iron and nickel, were formed 4.6 billion years ago, probably under the influence of a magnetic field. It is therefore possible that the primordial dust of iron granules has stored information about the magnetic field in the early solar system. This would be interesting information for researchers around the world because the magnetic field at that time may have influenced the development of the early solar system.
Put to the heat test
This is where the “TITAN”, with its electron holography, came into play. Shah and his colleagues from Great Britain, Norway and Jülich wanted to use it in order to prove that the magnetic structures of the samples had – for example due to temperature fluctuations – barely changed over the course of millions of years.
For this purpose, the researchers slowly heated the nano particles to up to 600 degrees – and exposed them to conditions as presumably prevailed in space in the past. The scientists wanted to see what this extreme treatment would do to the sample. The result was astonishing: the magnetic vortices remained stable.
For Shah, this was an extraordinary experiment: “For me, the test was a test of patience. The measurement itself took 13 hours and I only had one test because I had only received a single sample from the meteorite. The smallest mistake and the work would have been lost.”
Comparing the results of experiments with calculations subsequently proved that the magnetic information is actually stored much longer and more stably than had previously been assumed. In the case of the Bishunpur meteorite samples, the researchers are even convinced that the magnetic structures have not changed significantly over the course of billions of years. “The fact that metal grains of this kind are able to store age-old magnetic fields encourages us to investigate this aspect in more rocks. Maybe this will gradually provide us with a complete archive of the magnetisation of our early solar system,” Shah hopes.
“ For me, the test was a test of patience. The measurement itself took 13 hours and I only had one test.”
Medicine is to benefit
His colleague Trevor P. Almeida from the University of Glasgow, who was also intensively involved in the project, sees another possible benefit of the discovery: “The more and the better we understand nanostructures – such as now in the investigation of the 120-year-old meteorite – the sooner we could use them in other fields as well.” An example for the near future is nanomedicines. These could be implanted into diseased cells and then heated from the outside by magnetism in order to activate them. The active substances are first directed magnetically and specifically at the cancer cells that need to be destroyed. “We can learn how to do this by studying the magnetic structures in the meteorites. We will certainly require electron microscopy again for the necessary research into the structure of suitable active substances,” according to Almeida. There seems to be more work in store for the “TITAN” and its colleagues.
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Images: Pan_Da/Shutterstock.com, Forschungszentrum Jülich/Gabriele Wassenhoven, Luke de la Nougerede, Forschungszentrum Jülich/Ralf-Uwe Limbach