Rooftops of 3 major European cities yield samples of cosmic dust
Wednesday, 07 December 2016

Tiny particles dating back to the birth of the solar system some 4.6 billion years ago have been discovered on rooftops in Paris, Oslo and Berlin.

Previously, the space debris was only found in Antarctica and deep parts of the ocean, but this is the first time, cosmic dust has appeared in major cities.

Scientists looked through 300 kilograms of grime from the gutters of roofs in the three cities and used magnets to extract the particles, which also contain minerals consisting of magnetic materials. In the process, researchers discovered 500 cosmic dust grains.

The particles, which are roughly 0.01 millimetres in size, fell to earth after forming. Researchers hope that by analyzing the dust, scientists will be able to understand how the early solar system evolved.

Dr. Matthew Genge from the Department of Earth Science and Engineering at Imperial College London and amateur scientist Jon Larsen from Norway both teamed up for the project.

Larsen contacted his colleague in 2011 because he believed cosmic dust particles could be found in urban landscapes.

From the urban samples that were analyzed, researchers were able to understand that large amounts of cosmic dust recently fell to Earth.

"When Jon first came to me, I was dubious," Genge said. "Many people had reported finding cosmic dust in urban areas before, but when they were analysed, scientists found that these particles were all industrial in origin."

"We've known since the 1940s that cosmic dust falls continuously through our atmosphere, but until now we've thought that it could not be detected among the millions of terrestrial dust particles, except in the most dust-free environments such as the Antarctic or deep oceans. The obvious advantage to this new approach is that it is much easier to source cosmic dust particles if they are in our backyards," he added.

The particles discovered in urban areas, however, were larger than previous particles found, according to the study. They were around 0.3 millimeters.

Based on the size of the particles, analysis suggests that they were formed by melting as they entered the atmosphere at speeds of around 12km per second, making them the fastest moving dust particles found on the planet, according to Genge.

The study also found that cosmic dust has changed over the last million years. There were fewer feather-like crystals than the particles found in Antarctica, which racked up in ice over the last million years.

It is believed that the difference in the particles comes from changes in the orbits of planets in the solar system. Throughout millions of years, the orbits of planets varied slightly, causing disturbances in the gravity they exerted, influencing the trajectory of the microscopic particles as they traveled through space. All of this, according to the study, results in rising temperatures, which cause the crystals that grew in cosmic dust to form in different shapes and sizes.

"This find is important because if we look at fossil cosmic dust collected from ancient rocks to reconstruct a geological history of our solar system, then we need to understand how this dust is changed by the continuous pull of the planets," Genge said.

 



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