Scientists have discovered trace evidence of supernovae in sediments lining the sea floor.

Astrophysicist Shawn Bishop from the Technical University in Munich, Germany, had been studying fossilized bacteria to find trace elements of iron isotopes created out of supernova explosion about 2.2 million years ago.

But now, he has succeeded, confirming his 2013 findings in a new paper published in the journal Proceedings of the National Academy of Sciences. "The signal is definitely there," Bishop told Gizmodo.

Iron-60 or 60Fe is an isotope being produced by supernovae when they explode and scatter into space. 60Fe has a very short lifespan, which means there is no longer any trace of the element on Earth. However, traces of the isotope have been discovered in fossils of bacteria on the sea floor, Gizmodo reports.

According to Bishop, the evidence of isotope was contained in tiny microfossils of ancient bacteria scientists have discovered in the sea floor core sediment samples. Using accelerator mass spectrometry (AMS), Bishop analyzed the grains of bacteria inside the core samples taken from the floor of the Pacific Ocean and counted each 60Fe isotope atom one by one.

He found high concentrations of 60Fe in one of the cores that could be associated with supernova explosion about 2.2 million years ago. Bishop also identified some candidate stars in the Scorpio Centauri cluster.

Anton Wallner, a scientist from The Australian National University, conducted his own research to find more traces of 60Fe, together with an international team of researchers. In a study published in the journal Nature in April, Wallner detailed their discovery of nearby supernovae explosions millions of years ago, scattering radioactive particles into the Earth. According to the research team, the nearest of the explosions in an aging star cluster about 326 light years from the Earth.

According to scientists, either Bishop's confirmation study or Wallner's study could be related to the onset of the Pleistocene, which triggered a period of global cooling.