That was too late for any dynamo to be active, but it was also too late for sources like the churning gas and dust of the still - forming solar system to be responsible for the 2 - to 12 -
microteslas field identified in the meteorite.
The analysis shows that around the year 1370, field strength was falling by 0.054
microteslas a year — substantially faster than today's drop of 0.036 microteslas.
Specifically, the team found that the angrites» remnant magnetization could have been produced by an extremely weak magnetic field of no more than 0.6
microteslas, 4.563 billion years ago, or, about 4 million years after the start of the solar system.
In 2014, Weiss» group analyzed other ancient meteorites that formed within the solar system's first 2 to 3 million years, and found evidence of a magnetic field that was about 10 - 100 times stronger — about 5 - 50
microtesla.
Here we show that remanent magnetization in the eucrite meteorite Allan Hills A81001 formed during cooling on Vesta 3.69 billion years ago in a surface magnetic field of at least 2
microteslas.
Portrait of a young planet The Jack Hills zircons show that a magnetic field existed as early as 4 billion years ago, fluctuating in strength from a value similar to today's — around 25
microteslas — to about 12 % of that.
Generated by the flow of molten metal in its core, the Earth's magnetic field ranges from a mere 25
microteslas near the equator to 65 microteslas toward the poles — making it more than a hundred times weaker than a refrigerator magnet.