Published by JGR-Planets (vol. 131 #2):
Sato, M. Kimura, Y. Hatakeyama, T. et al. Characteristics of Natural Remanence Records in Fine‐Grained Particles Returned From Asteroid Ryugu 2025JE009265
The question of asteroid magnetic fields is a constant, unanswered one. Differentiated, iron meteorites clearly came from a body with some history of molten magma, producing some magnetic field. But what of unmelted, undifferentiated bodies- a far greater number? The question is open since fields may likely be weaker than our instruments can measure. Amateur meteorite hunters using magnets don’t help, because the use of magnets to spot meteorites can overwrite the meteorite’s own field.
Enter Hayabusa2, and its samples of Ryugu. The Haya2 scientists aren’t stupid enough to hold a magnet next to their precious grains, and ruin them. Here, we have some results on magnetic readings from them. Did the parent asteroid (larger and older than Ryugu) have flowing brine, or other mechanisms, forming a magnetic field, or perhaps one induced by the solar wind, or…?