After a long and dedicated search, scientists believe they have discovered trace elements from supernovae settled on the sea floor. Iron isotopes created from a supernova explosion 2.2 million years ago have found their way into fossilized bacteria taken from a sample of the sea bed floor – the only place they could still be found after all this time.
Astrophysicist Shawn Bishop from the Technical University of Munich, Germany, published a new paper in the Proceedings of the National Academy of Sciences detailing his findings and following up on the hunch he has been following for several years. According to Gizmodo, he used accelerator mass spectrometry to analyze bacteria found in core samples from the ocean floor, counting each and every iron-60 isotope atom he found.
Iron-60, or 60Fe, is one of many elements produced by supernovae during an explosion. After being dispersed around space, these elements eventually settle onto planets. Because of 60Fe’s short half-life, none of it should still be around on Earth. However, traces have been found in fossilized bacteria thought to have picked up the crystals from the sea bed long ago. When the bacteria die, 60Fe remains preserved in the fossil record.
Australian National University’s Anton Wallner also published a study in Nature earlier this year, solidifying the case for supernovae depositing 60Fe on Earth. He and his team estimate the closest explosion occurred about 326 light years away. It is thought that either this event or Bishop’s findings are related to the onset of the Pleistocene, which triggered a period of global cooling.