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Analysis of ice age under 80 thousand years helped to understand where the planet gets the iron-60 and how the flow of matter changes.
The Earth gathers tiny traces of an ancient star explosion every day. An international group led by the Helmholtz Center in Dresden-Rossendorf found radioactive iron-60 in the Antarctic ice and linked the find with the interstellar cloud, through which the solar system is now passing. Posts Tagged ‘physical Review’s.
Iron-60 is born inside massive stars and enters space after supernovae. Geological archives have already shown that millions of years ago, the solar system at least twice fell under the flow of iron-60 from stellar explosions. In the last tens of thousands of years, there have been no such events nearby, so traces of the radioactive isotope in fresh Antarctic snow have long remained a mystery.
The main version of the researchers is as follows: iron-60 is stored in the Local Interstellar Cloud, a rarefied area of gas and dust between the stars. The solar system entered the cloud tens of thousands of years ago, and the Earth began to gradually collect matter from the environment. Scientists assumed such a mechanism before, but there was not enough evidence.
The new analysis helped close the gap. The team studied ice age from 40 000 to 80 000 years, obtained as part of the European drilling project EPICA. Samples were provided by the Alfred Wegener Institute of Polar and Marine Research. Comparison with previous data on deep-sea deposits and surface snow showed that less iron-60 got into ancient ice than in later periods and the modern era.
This result is poorly consistent with the version of the slowly attenuating trace of supernovae that exploded millions of years ago. If the Earth simply passed through the residual plume of the old event, the flow of the isotope would have changed otherwise. But the data falls well in the picture where the solar system moves through a heterogeneous interstellar cloud, and the content of iron-60 depends on the density and composition of the surrounding gas.
The researchers processed about 300 kilograms of ice. After chemical preparation, only a few hundred milligrams of dust remained from the huge mass. At each stage, the team checked whether iron-60 was lost along with the material, and checked the result on other radioisotopes - beryllium-10 and aluminum-26. Their expected concentrations in the ice are well known, so the losses would immediately spoil the control picture.
The final measurements were held at the Heavy Ion Accelerator Facility at the Australian National University. According to the authors, the installation now remains the only one in the world that is able to confidently find such small amounts of iron-60. The device separated the excess atoms with electrical and magnetic filters, until among the 10 trillion initial atoms there was literally a handful of atoms of the desired isotope.
The authors are already preparing the next stage. Researchers want to study even more ancient ice that formed before the solar system enters the Local Interstellar Cloud. Such cores should show how the flow of iron-60 to the contact with the cloud changed, and will help to more accurately restore the history of matter left by longtime stellar explosions.
The Earth gathers tiny traces of an ancient star explosion every day. An international group led by the Helmholtz Center in Dresden-Rossendorf found radioactive iron-60 in the Antarctic ice and linked the find with the interstellar cloud, through which the solar system is now passing. Posts Tagged ‘physical Review’s.
Iron-60 is born inside massive stars and enters space after supernovae. Geological archives have already shown that millions of years ago, the solar system at least twice fell under the flow of iron-60 from stellar explosions. In the last tens of thousands of years, there have been no such events nearby, so traces of the radioactive isotope in fresh Antarctic snow have long remained a mystery.
The main version of the researchers is as follows: iron-60 is stored in the Local Interstellar Cloud, a rarefied area of gas and dust between the stars. The solar system entered the cloud tens of thousands of years ago, and the Earth began to gradually collect matter from the environment. Scientists assumed such a mechanism before, but there was not enough evidence.
The new analysis helped close the gap. The team studied ice age from 40 000 to 80 000 years, obtained as part of the European drilling project EPICA. Samples were provided by the Alfred Wegener Institute of Polar and Marine Research. Comparison with previous data on deep-sea deposits and surface snow showed that less iron-60 got into ancient ice than in later periods and the modern era.
This result is poorly consistent with the version of the slowly attenuating trace of supernovae that exploded millions of years ago. If the Earth simply passed through the residual plume of the old event, the flow of the isotope would have changed otherwise. But the data falls well in the picture where the solar system moves through a heterogeneous interstellar cloud, and the content of iron-60 depends on the density and composition of the surrounding gas.
The researchers processed about 300 kilograms of ice. After chemical preparation, only a few hundred milligrams of dust remained from the huge mass. At each stage, the team checked whether iron-60 was lost along with the material, and checked the result on other radioisotopes - beryllium-10 and aluminum-26. Their expected concentrations in the ice are well known, so the losses would immediately spoil the control picture.
The final measurements were held at the Heavy Ion Accelerator Facility at the Australian National University. According to the authors, the installation now remains the only one in the world that is able to confidently find such small amounts of iron-60. The device separated the excess atoms with electrical and magnetic filters, until among the 10 trillion initial atoms there was literally a handful of atoms of the desired isotope.
The authors are already preparing the next stage. Researchers want to study even more ancient ice that formed before the solar system enters the Local Interstellar Cloud. Such cores should show how the flow of iron-60 to the contact with the cloud changed, and will help to more accurately restore the history of matter left by longtime stellar explosions.
