For decades, scientists have been trying to understand why some rocks on the moon are strongly magnetized even though the moon has no magnetic field today.
Moon rocks brought to Earth during NASA's Apollo missions in the 1960s and '70s, as well as data from orbiting spacecraft, have shown that parts of the lunar surface — particularly on the farside — contain rocks with surprisingly strong magnetic signatures. New computer simulations suggest a massive asteroid impact billions of years ago may have briefly amplified the moon's old, weak magnetic field, leaving behind a magnetic imprint still detectable in lunar rocks.
