THE belief that Mars’s magnetism died out nearly four billion years ago could be wrong. If a study of a meterorite crater in South Africa is anything to go by, the Red Planet may have been magnetically active long after that.
Measurements taken by the Mars Global Surveyor satellite have shown that the massive Hellas and Argyre craters are only weakly magnetic. Scientists took this to mean that Mars’s magnetism was already weak when meteorites struck to form the craters four billion years ago. This conclusion was based on the idea that if the magnetic field was weak to being…
