Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Europan Ocean on 08/07/2013 08:25:33

Title: Cobalt in the Earth's core?
Post by: Europan Ocean on 08/07/2013 08:25:33

Is there a large percentage of cobalt in the Earth's core? Can a planet generate a magnetosphere with Cobalt?

Title: Re: Cobalt in the Earth's core?
Post by: evan_au on 10/07/2013 14:19:18

The core of the Earth (http://en.wikipedia.org/wiki/Inner_core#Composition) is believed to consist mainly of a nickel-iron alloy, similar to nickel-iron meteorites.
Other elements are mixed in with this alloy, and cobalt is one of the most common of the minor components.

Cobalt (http://en.wikipedia.org/wiki/Cobalt#Characteristics) is a ferromagnetic metal, which means that it responds strongly to magnetism at room temperature. However, temperatures in the Earth's outer core are believed to be in the range 4400C-6100C, well above Cobalt's Curie temperature of 1115C, so it will not be magnetic in this environment (nor will iron, with a Curie temperature of 770C or Nickel, at 355C).

The Earth's magnetic field is thought to be produced by electrical currents in the Earth's liquid outer core (http://en.wikipedia.org/wiki/Outer_core), driven by convection and possibly differential rotation between the inner core and the mantle. These currents do not need to occur in a magnetic material - laboratory experiments to reproduce the effect have used liquid Sodium, which is non-magnetic.

So to summarise - there is some Cobalt in the Earth's core, and a magnetic field can be generated in a molten Nickel-Iron alloy that contains Cobalt.