Science:
An analysis of the magnetic fields recorded in a meteorite that
originated on Vesta may prove that the asteroid once had a
molten core. By progressively demagnetizing samples from the
meteorite, a team led by MIT's Roger Fu was able to identify a
weak magnetic field dating to about 3.7 billion years ago.
However, that is approximately 1 billion years after Vesta's
core stopped rotating and generating a magnetic field. As Vesta
cooled, the rotating core would have imprinted a magnetic field
into the crystals that formed in the asteroid's crust. Fu's
team believes that an impact by another asteroid melted the
area of the crust where the meteorite originated from, erasing
the original magnetic field imprint. The field that the team
detected would have been imprinted by the magnetic fields in
the nearby areas of the crust that were not melted by the
asteroid collision. An impact from yet another asteroid would
have ejected debris, of which the meteorite that Fu examined
was part.
