Earth could be traveling through remains of star explosions for last 33,000 years, say scientists
For the last 33,000 years, Earth seems to be running into stardust or a cloud of radioactive dust. Parts of it could have rained down on Earth, ending up buried in the deep-sea, according to a new study. In the deep sea, researchers from Australian National Univesity found a version of iron called iron-60. It is not naturally produced on Earth or within the solar system in significant amounts. Instead, its origins can be traced to a star's explosive death or supernova.
Supernova explosions, a powerful and super bright explosion of a star, could leave behind dust clouds, lead author Professor Anton Wallner, previously said in a statement. The clouds contain radioactive iron called iron-60, which then showered into our planet."Iron-60 from space is a million-billion times less abundant than the iron that exists naturally on Earth," Dr Wallner said.
Iron-60 is radioactive. It requires 15 million years to decay completely. Earth, on the other hand, is 4.6 billion years old. This suggests the iron-60 detected on our plane has come from a recent, nearby explosion. This is not the first time scientists have detected iron-60 traces on Earth. Previously, experts found them in Antarctic snow. They speculated that the element came from the interstellar neighborhood. "As there are no natural sources for this radioactive isotope on Earth, we knew that the iron-60 must have come from a supernova," they said in a statement.
Even Wallner and his colleagues found traces of iron-60, which were dated to 2.6 million years and around six million years ago. The finding suggested that there were a series of supernova, one following the other.
In this study, Dr Wallner and his colleagues looked at various deep-sea sediments for traces of iron-60 from two different locations. Their analysis showed that the radioactive element, dating back to 33,000 years. As for its source, it could be coming from a bubble of gas and cloud called the local interstellar cloud (LIC), the team speculated. For more than thousands of years, the solar system appears to be passing through this cloud. It is about 30 light-years wide and contains hydrogen and helium, according to NASA. But a lot about LIC continues to remain mysterious.
Though their findings suggest that LIC could be involved, the evidence does not add up because the iron-60 extended further back and was spread throughout the entire 33,000 year measurement period, according to the experts. This has raised two questions: If a supernova did not give rise to the cloud, what was the origin? And why is iron-60 so evenly spread across space?
"There are recent papers that suggest iron-60 trapped in dust particles might bounce around in the interstellar medium," Dr Wallner said. "So the iron-60 could originate from even older supernovae explosions, and what we measure is some kind of echo. More data is required to resolve these details," he added.
The study is published in PNAS.