What is the magnetosphere?

The Earth has a magnetic field because it is a big magnet, which is good because the magnetic field prevents solar wind and cosmic rays from striking the Earth. There are magnetic north and south poles (which are not located precisely at the true north and south poles). This is why magnetic compasses function.

As it stands, a trip to Mars would be a death sentence for whoever went there. Other bodies have magnetospheres (the sun has a really powerful one), but some bodies have almost no magnetosphere at all. Mars has such a weak magnetosphere that any space exploration that occurs there is going to have to find a different way to protect itself from solar wind and cosmic rays.

The magnetosphere is the region surrounding a planet where the planet's magnetic field interacts with the solar wind, a stream of charged particles emitted by the Sun. It acts as a protective barrier, deflecting most of the solar wind and preventing it from reaching the planet's surface. The shape and size of a planet's magnetosphere are determined by its magnetic field strength and the pressure of the solar wind.