Topic: Shields Up: Magnetized Rocks Push Back Origin of Earth's Magnetic Field

[sam]

Earth's robust magnetic field protects the planet and its inhabitants from the full brunt of the solar wind, a torrent of charged particles that on less shielded planets such as Venus and Mars has over the ages stripped away water reserves and degraded their upper atmospheres. Unraveling the timeline for the emergence of that magnetic field and the mechanism that generates it—a dynamo of convective fluid in Earth's outer core—can help constrain the early history of the planet, including the interplay of geologic, atmospheric and astronomical processes that rendered the world habitable.

http://www.scientificamerican.com/article.cfm?id=geodynamo-start-up

[Clive]

Earth's churning interior produced a protective magnetic field as early as 3.45 billion years ago, closer to when life began

I don't think we should be surprised at that! 

[sam]

nope. Fairly simple physics really. That and of course god had to do that in day 2..