Implication for ET search: Earth's magnetic field older than believed
Stones found in Greenland were magnetized 3.7 billion years ago. This would also have consequences for the search for extraterrestrial life.
(Bild: Andrey VP/Shutterstock.com)
The Earth's magnetic field is considerably older than assumed, and could therefore have already existed when life developed on Earth. This has been determined by a research group using rock samples from Greenland, which are thought to be 3.7 billion years old and show traces of magnetization. Previously, there had only been evidence of a geomagnetic field 3.5 billion years ago. The new research now suggests that the magnetic field of our home planet could have played a decisive role in the emergence of life. At the same time, however, it is unclear by which processes it was formed in the first place, as the Earth's inner core, which is involved today, is not thought to have existed at that time.
Planetary magnetic fields much more common?
Geologist Claire Nichols, who led the analysis, explains that it is assumed that the Earth's magnetic field makes a decisive contribution to the fact that our planet is livable and has remained so for so long. It protects us from harmful radiation from space and makes the formation and existence of oceans and the atmosphere possible in the first place. If it was driven by a different process in the early days of our home planet than it is now, this could also mean that there is more than one possible process that generates a strong magnetic field on other planets. This would mean that life-friendly conditions could be much more common than expected.
The trace of the Earth's magnetic field at that time was found in rare rocks lying on the surface in a remote region of Greenland. The "beautiful, strange stones" were formed when iron dissolved in the water accumulated on the seabed. The Earth's magnetic field at the time magnetized it and this magnetization was not lost in the billions of years that followed, despite two phases of strong heating. The research group was even able to determine that the magnetic field had a strength of at least 15 microtesla 3.7 billion years ago. This would be about half as strong as at the equator today, so in principle of a comparable order of magnitude. The study is presented in the Journal of Geophysical Research.
(mho)