Planetary core has an observed magnetic field, which is believed to be generated within its metallic core. Mercury's core occupies 85% of the planet's radius, making it the largest core relative to the size of the planet in the Solar System; this indicates that much of Mercury's surface may have been lost early in the Solar System's history. Mercury has a solid silicate crust and mantle overlying a solid iron sulfide outer core layer, followed by a deeper liquid core layer, and then a possible solid inner core making a third layer. The composition of Venus' core varies significantly depending on the
Oceanic crust frozen in the basalt. A symmetrical pattern of positive and negative magnetic lines emanates from the mid-ocean ridge. New rock is formed by magma at the mid-ocean ridges, and the ocean floor spreads out from this point. When the magma cools to form rock, its magnetic polarity is aligned with the then-current positions of the magnetic poles of the Earth. New magma then forces the older cooled magma away from the ridge. This process results in parallel sections of oceanic crust of alternating magnetic polarity. Oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of a tectonic