MARS has a liquid outer core of iron, some 3040 to 3680 kilometres across.
Planetary scientists at NASA’s Jet Propulsion Laboratory in California made the discovery after realising that the orbit of the Mars Global Surveyor had changed by a minuscule amount. That could only happen if the Sun’s gravity tugs at a liquid core in Mars, inducing subtle deformations in its shape.
The discovery was fortuitous, says Charles Yoder of the JPL, as the probe just happens to orbit so it always sees sunlight hitting the surface at an angle of 30°, providing a baseline against which researchers could…
