I’m generally not into rocks, but I have to admit that we can learn an amazing amount of science by studying all the different physical properties of rocks. In another paper centered on rocks, we learn that our own Earth may have had a massive magma ocean 4 billion to 2.5 billion years ago. Our world is still hot – nuclear decays across the depths of our planet continue to generate heat that churns our planet’s internal heat flows. Today, this churning magma – specifically Earth’s outer liquid iron / nickel core – plays a key role in generating Earth’s magnetic field. Historically, however, this was not the source.

Figuring out the origins of the Earth’s magnetic field hasn’t been easy, and scientists have struggled to figure out how our planet went from a generic lump of melty rocks to being a coherent planet with a well defined magnetic field. In new research coming out in Nature Communications, planetary scientists have used computer models to figure out that the early Earth would have had a massive molten silicates – minerals that include silicon. Lead author Lars Strixrude modeled how these minerals behave had high temperatures and found that they are conductive enough to generate magnetic fields. While these silicates cooled and solidified over the Earth’s first few billion years, they were liquid long enough to allow the Earth’s increasingly turbulent core to reach a point where it could take over magnetic field generation.

That hand-off from the Earth’s magnetic field coming from a liquid silicate dynamo to later coming from a liquid iron/nickel dynamo allowed our world to have magnetism from as early as possible, and more-or-less continually to the present day. This has protected our evolving atmosphere, and made life possible. This physics doesn’t look like it will be unique to our world. While Earth is unusually dense because of how it was formed, and has an unusually large iron/nickel core, this kind of a silicate magma driven magnetism could be common on super earths. These larger worlds would have longer lasting silicate magma seas. These are also the most common smaller worlds that we’ve found, and we now see amazing ways those worlds could be a bit safer for life.

More on this can be found at:

An ancient magma ocean may have once driven Earth’s magnetic field (Science News)