Scientists discover Earth passing through ancient supernova debris hidden in Antarctic ice

Think of stepping out on a cool evening and gazing into the night sky and knowing that the air above you is filled with an invisible whisper from a star that died long ago. It sounds like the beginning of a science fiction movie. But new research in space shows that the whole planet is actually floating through the literal debris of an ancient supernova.By analysing ice samples dug up from deep within the frozen wastes of Antarctica, scientists have opened a cosmic history book. These frozen vaults hold specks of star dust that survived a journey through space, settling silently into our atmosphere over thousands of years.Frozen secrets of the cosmic deep pastAn international research team headed to one of the most remote places on Earth to find these tiny pieces of space history. Led by scientists at the Helmholtz-Zentrum Dresden-Rossendorf, the team examined ice cores from between 40,000 and 80,000 years ago. They were searching for a very particular and rare radioactive isotope, called iron-60.This particular kind of iron does not occur naturally on Earth. It is forged deep inside the explosive hearts of huge stars and only blasted out into the universe when those stars explode and collapse. It decomposes with age, so if we find fresh traces of it in younger geological layers, it must have recently arrived in our vicinity.A study, published in Physical Review Letters, reveals how our solar system is currently traversing a giant cosmic cloud called the Local Interstellar Cloud. This interstellar cloud is a bit like a giant storage unit for ancient stardust, retaining the radioactive material from an explosion long ago. Our Sun and its planets plough through this region of space, and Earth acts like a giant windscreen, collecting the drifting dust. Cosmic dust in a giant haystackIt took a lot of patience and some of the most sensitive scientific equipment in the world to prove this theory. The researchers had to haul some 300 kilograms of pristine Antarctic ice to a lab in Germany for processing. That massive pile of snow was melted and subjected to complex chemical treatments to yield just a few hundred milligrams of fine dust.The laboratory staff monitored the extraction with other stable isotopes, like beryllium-10 and aluminium-26, to make sure no valuable space particles were lost during the processing. The final, crucial test was performed at the Heavy Ion Accelerator Facility of the Australian National University. This special facility uses powerful magnetic and electrical filters to separate individual atoms according to their mass.Finding the iron-60 atoms, the research team said, is like searching for a single needle buried in 50,000 football stadiums full of hay. But the advanced accelerator could identify the individual radioactive atoms among trillions of others in just about an hour.In the end, the data revealed that the iron-60 falling on Earth tens of thousands of years ago was much smaller than what falls on the surface today. This means the cosmic cloud we are travelling through has very lumpy patches of density, or that our solar system has just entered the thicker, dustier part of the stellar debris.Some tens of thousands of years ago, scientists estimate we entered the outer edges of this interstellar cloud. We are supposed to keep drifting in its radioactive haze for a few thousand more years before finally emerging back into the clearer, open lanes of the galaxy. Until then, each snowfall in winter is a microscopic reminder of the violent, beautiful cycle of stellar life and death.