The long-dead magnetic field of Mars could eventually come back to life if the results of a new experiment are correct. The study, which suggests that Mars' core is mostly or completely liquid, may also help scientists unravel the mystery of why the planet’s magnetic field shut off billions of years ago.

It has been known since 2003 that at least part of Mars' interior is molten, based on how easily the Sun’s gravity distorts the planet’s shape, but no one knew whether it is completely liquid, or whether there is a solid inner core like Earth's.

Now a team of scientists, led by Andrew Stewart of the Swiss Federal Institute of Technology in Zurich, Switzerland, has succeeded in creating in the lab the high pressure and temperature expected in Mars' core.

Using chambers made of diamond, they compressed mixtures of iron, nickel and sulphur up to the maximum pressure expected in Mars' core, which is 40 gigapascals - 400,000 times the pressure of Earth's atmosphere at sea level.