Supernovae showered Earth with radioactive debris

Supernovae showered Earth with radioactive debris
Artist's impression of supernova. Credit: Greg Stewart, SLAC National Accelerator Lab

An international team of scientists has found evidence of a series of massive supernova explosions near our solar system, which showered the Earth with radioactive debris.

The scientists found radioactive iron-60 in sediment and crust samples taken from the Pacific, Atlantic and Indian Oceans.

The iron-60 was concentrated in a period between 3.2 and 1.7 million years ago, which is relatively recent in astronomical terms, said research leader Dr Anton Wallner from The Australian National University (ANU).

"We were very surprised that there was debris clearly spread across 1.5 million years," said Dr Wallner, a nuclear physicist in the ANU Research School of Physics and Engineering. "It suggests there were a series of supernovae, one after another.

"It's an interesting coincidence that they correspond with when the Earth cooled and moved from the Pliocene into the Pleistocene period."

The team from Australia, the University of Vienna in Austria, Hebrew University in Israel, Shimizu Corporation and University of Tokyo, Nihon University and University of Tsukuba in Japan, Senckenberg Collections of Natural History Dresden and Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany, also found evidence of iron-60 from an older supernova around eight million years ago, coinciding with global faunal changes in the late Miocene.

Some theories suggest cosmic rays from the supernovae could have increased cloud cover.

A supernova is a massive explosion of a star as it runs out of fuel and collapses.

Supernovae showered Earth with radioactive debris
False color image of Cassiopeia A using Hubble and Spitzer telescopes and Chandra X-ray Observatory. Credit: NASA/JPL-Caltech

The scientists believe the supernovae in this case were less than 300 light years away, close enough to be visible during the day and comparable to the brightness of the Moon.

Although Earth would have been exposed to an increased cosmic ray bombardment, the radiation would have been too weak to cause direct biological damage or trigger mass extinctions.

The supernova explosions create many heavy elements and which are strewn into the cosmic neighbourhood.

One of these isotopes is iron-60 which decays with a half-life of 2.6 million years, unlike its stable cousin iron-56. Any iron-60 dating from the Earth's formation more than four billion years ago has long since disappeared.

The iron-60 atoms reached Earth in minuscule quantities and so the team needed extremely sensitive techniques to identify the interstellar iron atoms.

"Iron-60 from space is a million-billion times less abundant than the iron that exists naturally on Earth," said Dr Wallner.

Supernovae showered Earth with radioactive debris
Anton Wallner. Credit: Stuart Hay

Dr Wallner was intrigued by first hints of iron-60 in samples from the Pacific Ocean floor, found a decade ago by a group at TU Munich.

He assembled an international team to search for interstellar dust from 120 ocean-floor samples spanning the past 11 million years.

The first step was to extract all the iron from the ocean cores. This time-consuming task was performed by two groups, at HZDR and the University of Tokyo.

The team then separated the tiny traces of interstellar -60 from the other terrestrial isotopes using the Heavy-Ion Accelerator at ANU and found it occurred all over the globe.

The age of the cores was determined from the decay of other radioactive isotopes, beryllium-10 and aluminium-26, using (AMS) facilities at DREsden AMS (DREAMS) of HZDR, Micro Analysis Laboratory (MALT) at the University of Tokyo and the Vienna Environmental Research Accelerator (VERA) at the University of Vienna.

The dating showed the fallout had only occurred in two time periods, 3.2 to 1.7 million years ago and eight million years ago. Current results from TU Munich are in line with these findings.

A possible source of the supernovae is an ageing star cluster, which has since moved away from Earth, independent work led by TU Berlin has proposed in a parallel publication. The cluster has no large stars left, suggesting they have already exploded as supernovae, throwing out waves of debris.


Explore further

Physicists reach new milestone measuring half-life of iron-60

More information: Recent near-Earth supernovae probed by global deposition of interstellar radioactive 60Fe, Nature, DOI: 10.1038/nature17196
Journal information: Nature

Citation: Supernovae showered Earth with radioactive debris (2016, April 6) retrieved 22 October 2019 from https://phys.org/news/2016-04-supernovae-showered-earth-radioactive-debris.html
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Apr 06, 2016
Our Sun is perfectly capable of producing iron-60.

Apr 06, 2016
"The scientists believe the supernovae in this case were less than 300 light years away, close enough to be visible during the day and comparable to the brightness of the Moon."

The diameter of the rest of supernovae is a maximum of 200 ly. The remaining 150 ly matter teleport exclusively to Earth.

P.S. The remains of supernovae have no heavier elements, they are teleported from other dimensions.

Apr 07, 2016
Just a wild guess...but OTOH, if the Earth wasn't in the direct line of "fallout" from the supernova, and was instead in a position (due to its orbit around the Sun) to avoid the full brunt of the incoming radioactive interstellar Iron-60, perhaps it was that the Earth was "protected" somewhat by the Solar Wind which could have lessened the effects from the Cosmic Wind and its radioactive particles. "The iron-60 atoms reached Earth in minuscule quantities..." according to the article.
Mars, depending on where within its own orbit it happened to be at the time that the Iron-60 infiltrated into the SS, may have received a larger dose than the Earth. That should be yet another experiment to be carried out by a rover so equipped for it.

Apr 07, 2016
I know very well the isotopic dating methods and can not stop to wander how some scientists believe in science fiction stories for the billion years old Earth when they can not deternmine when are started izotopic clocks in different samples. Because they do not know what was the prior proportion of isotopes when these clocks are started to work and what was the impact of the physical environment on them during their work in real period of time.
This is not true science but nothing more than speculative sham.


Apr 07, 2016
"Some theories suggest cosmic rays from the supernovae could have increased cloud cover." Svensmark's cosmic ray theory! What will the warmists say about this?

Apr 07, 2016
"Some theories suggest cosmic rays from the supernovae could have increased cloud cover." Svensmark's cosmic ray theory! What will the warmists say about this?
- sstritt
There will be some loud rumblings and squealing like stuck pigs from those AGWites who are still flying in airplanes and helicopters that are powered by jet fuel. Not to mention those who drive "solar" cars that are still, for the most part, recharged from the grid; cars being indirectly powered by fossil fuels.
Oh, the humanity!!
LOL

Apr 07, 2016
I know very well the isotopic dating methods and can not stop to wander how some scientists believe in science fiction stories for the billion years old Earth when they can not deternmine when are started izotopic clocks in different samples. Because they do not know what was the prior proportion of isotopes when these clocks are started to work and what was the impact of the physical environment on them during their work in real period of time.
This is not true science but nothing more than speculative sham.
- Viko
That's ~3.6 Billion years. I have studied Genesis, and I assure you that the Earth's age is NOT 6000 - 7000 yrs. It was Jewish miscalculation of Earth's age when those authors decided to add up the ages of each generation from Adam going forward. It is a result of HUMAN error; specifically JEWISH HUMAN error that has caused all the geological misconceptions by believers in the Hebrew Bible. They didn't have the tools that we now have.

Apr 07, 2016
"Some theories suggest cosmic rays from the supernovae could have increased cloud cover." Svensmark's cosmic ray theory! What will the warmists say about this?

Warmists? What an empty-headed comment! Hey genius, you are aware the world is not cooling right? Maybe you should actually read his theory before making such uninformed comments.

Warmists! What a moron.

Apr 09, 2016
Our Sun is perfectly capable of producing iron-60.


It is a H/He fusion star, so not at this stage. You have to wait until it starts fusing C, then O et cetera in the red giant stage. As far as I know Sun is too small to get to the fused iron stage.

Warmists


Well, the world is warning and there are no supernovas around, so their effect on cloud cover is irrelevant. Instead it is now known from data alone that man made CO2 release is the main driver.

Apr 09, 2016
Let's start with, what star cluster specifically, and where are the supernova remnants from all this activity?

If there's corroborating data about this, it should have been linked. This article is incomplete without that data.

Apr 09, 2016
"Some theories suggest cosmic rays from the supernovae could have increased cloud cover." Svensmark's cosmic ray theory! What will the warmists say about this?
Show the decreased cosmic ray flux that accounts for global warming. Show the "higher solar activity" that is claimed to have caused this lower cosmic ray flux, consistently since the beginning of the 20th Century. Good luck with that.

Then there's the fact that Svensmark manipulated the data in several ways, including "adjusting" the lower cloud data, after it had been shown that there was no correlation between high cloud cover and cosmic ray influx despite his earlier claim to the contrary. This is fudging and most scientists have dismissed Svensmark's "theory" as smoke.

Source: http://stephensch...2003.pdf

Apr 09, 2016
The paper linked above, Laut 2003, is pretty much the end of the conversation. Svensmark first claimed total cloud cover, then when it was obvious this was smoke, retreated to low cloud cover and made-- note this, this guy is supposed to be a professional scientist-- *arithmetic* errors in stating even the low cloud cover he'd retreated to. Whatever he might have done in astrophysics, he's totally incompetent to comment on geophysics and should be reprimanded for trying to sneak this stuff past the referees.

Apr 12, 2016
Our Sun is perfectly capable of producing iron-60.


It is a H/He fusion star, so not at this stage. You have to wait until it starts fusing C, then O et cetera in the red giant stage. As far as I know Sun is too small to get to the fused iron stage.

Warmists


Well, the world is warning and there are no supernovas around, so their effect on cloud cover is irrelevant. Instead it is now known from data alone that man made CO2 release is the main driver.
- TBL
There is also the CO2 being emitted from the East African Rift (EAR), as well as from volcanic action and undersea bubbles of CO2 and CH4 gases coming up from the ocean floor. All working together. Your manmade GHG can be cut back but never eliminated entirely. But Nature will continue to take its course and cannot be harnessed by AGWites.

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