Planetary Science Institute | 2020 May 01
A Martian magnetic field was in place much earlier – as well as much later – than scientists had thought ...
A planet’s global magnetic field arises from what scientists call a dynamo: a flow of molten metal within the planet’s core that produces an electrical current. On Earth, the dynamo is what makes compass needles point north. But Mars’ dynamo, and magnetic field, has been extinct for billions of years.
"We have these two observations that point to a dynamo at the earliest known time in Mars' history, and a dynamo that was present almost half a billion years after many people thought it had already switched off," Johnson said.
"We find that the Martian dynamo operated at 4.5 billion years ago (4.5 Ga) and 3.7 billion years ago. Dynamo timing is a big part of a planet’s evolution, and what we find is very different from what we have thought so far," said Anna Mittelholz ... “The dynamo tells us something about the planet's thermal history, its evolution, and how it got to where it is today, and it is unique for each of the terrestrial planets – Earth, Mars, Venus and Mercury.” ...
Timing of the Martian Dynamo: New Constraints for a Core Field 4.5 and 3.7 Ga Ago ~ A. Mittelholz et al
- Science Advances 6(18):aba0513 (01 May 2020) DOI: 10.1126/sciadv.aba0513