Our planet is surrounded by a magnetic field that acts as a shield.

It keeps the solar wind away from the top of our atmosphere, preventing it from scrubbing our atmosphere away, and reduces the consequences for us of the Sun's bad behaviour. This magnetic shield is generated by electric currents flowing in our planet's liquid interior.

Mars is an example of what happens when that magnetic field disappears. Being a smaller world, it cooled faster and its interior solidified. The electric currents ceased to be generated and the magnetic field largely vanished, allowing the solar wind to start scrubbing away at the atmosphere.

Today, Mars' surface is a frigid, almost airless desert. Our planet is much larger than Mars, and therefore cooling more slowly, so solidification of its interior lies a long way off. However, recent research suggests a situation that is more complicated.

In the 1960s, magnetometers—devices for measuring the strength and direction of magnetic........

© Castanet