We fly through a cloud of debris from a supernova explosion

Radioactive dust on the ocean floor indicates that the Earth is flying through a massive cloud created by a star explosion.

Over the past 33,000 years, a multitude of rare iron isotopes, which are formed in supernova explosions, have fallen from space to Earth.

Of course, this is not the first time the iron-60 isotope has fallen to our planet. But now scientists have more and more evidence that the process continues today - still moving through an interstellar cloud of dust formed several million years ago in a supernova explosion.

What is iron-60?

Żelazo-60 has been the subject of many studies over the years. The half-life of this element is 2.6 million years, which means that it is completely decayed within 15 million years. It can therefore be concluded that any samples found on Earth must come from outside our planet, as iron-60 would not have survived since its formation 4.6 billion years ago.

And in fact, iron-60 can actually be found on Earth. Anton Wallner, a nuclear physicist at the Australian National University, dates isotope deposits in the ocean floor to 2.6 and 6 million years, indicating that it was during these times that they fell to Earth from space.

However, we also have younger deposits - much younger ones

Traces of iron-60 were also found in snow in Antarctica. Preliminary studies indicate that they appeared there in the last 20 years.

A few years ago, researchers announced that they had been recording the presence of iron-60 in space around the Earth for 17 years using the Advanced Composition Explorer probe.

Now Wallner has found more iron deposits in five different seabed sediment samples collected at two different locations and going back 33,000 years. The amount of iron-60 in these samples is more or less constant throughout this period. The problem is that such a discovery raises more questions than it answers.

The Earth is flying through the interstellar cloud

The Earth is currently moving through the so-called The Local Interstellar Cloud is composed of gas, dust and plasma. If this cloud was formed by a supernova explosion, it is perfectly understandable that iron-60 is constantly falling to Earth. This is at least what the Antarctic data shows, and that is what Wallner wanted to confirm by analyzing ocean sediments.

On the other hand, if the Local Interstellar Cloud is a source of iron-60, we should observe a rapid increase in the amount of iron-60, from the moment the Solar System entered this cloud, that is during the last 33,000 years. The oldest sample should have a much lower iron-60 level. It is not so.

It is possible, of course, that the Local Interstellar Cloud is not a supernova remnant at all, but just right where the Solar System is now, and by the way we are passing through a supernova remnant. In such a situation, iron-60 would fall to Earth both before and after it enters the cloud.

Several recent papers indicate that iron-60 trapped among the dust particles can reflect off them in the interstellar medium. So perhaps the iron comes from a supernova millions of years ago, and we only see some echo of that outburst, says Wallner.

The puzzle may be solved by finding iron-60, which arrived on Earth between 40,000 and a million years ago. If it turns out that the farther we go back in time, there is more iron, it would indicate a source in a supernova from millions of years ago. However, if there is more iron in the last tens of thousands of years than before, this would mean that the Local Interstellar Cloud is a source of iron-60 after all.

We fly through a cloud of debris from a supernova explosion