Astronomy
Why Mars Lost Its Global Magnetic Field
Quick fact
Despite losing its global magnetic field billions of years ago, Mars retains 'fossilized' magnetic fields in its ancient crust, which provide evidence that a dynamo once raged in its core.
Why this is interesting
Earth's magnetic field acts as a shield against the solar wind, but Mars – once a warmer, wetter world – has no such shield today. What happened to it?