From MARK STOCK
Has anyone considered this possible explanation for ‘impossible’ Mercury’s
improbable magnetic field? (‘Mercury, the impossible planet’, 1 June).
If a bar of soft iron is aligned with the Earth’s magnetic field and
struck smartly with a hammer, it becomes weakly magnetised. On a grander
scale, take one small planet with a solid iron core, place it within the
Sun’s magnetic field and strike it smartly with a large asteroid (the Wetherill
scenario). The result: a weakly magnetised planet without the need to invoke
a molten interior.
Mark Stock Kings Norton, Birmingham
