Electric Universe

March 1, 2011

In the very center of Areios is the core, a dense ball of iron and nickel that sloshes around inside the planet, generating a magnetic field like the one on Earth. The core is divided into an inner and outer layer, based on density and these two layers spin at different rates, causing a magnetic field to form from an induced dipole moment. The magnetic field on Earth is generated by the molten iron and nickel that gets swirled around by the tug of the Earth’s orbit. The magnetic field was actually induced by the magnetic field generated from the Sun, and kept going by the motion of the liquid iron outer core which can conduct electricity as it was churned by the Coriolis Effect.Magnetic Pole reversal

Because Areios will take longer to cool, its core won’t differentiate into inner and outer layers until much later in time relative to how it happened on Earth. Because the core won’t differentiate at first, there won’t be a magnetic field on Areios until the planet’s insides settle down. This is important because that magnetic field keeps solar wind from stripping the atmosphere away and it keeps out deadly radiation that would attack the organic machinery of cells. In the book The Life and Death of Planet Earth, Peter Ward describes what some astrobiologists believe happened to Venus and Mars when the magnetic field of a planet stops; solar wind tears water into hydrogen and oxygen, boiling away the atmosphere until the atmospheric pressure prevents water from collecting on the surface at any temperature. The result: a dry and frozen world like Mars, or a dry and broiling world like Venus. Because Areios won’t develop a magnetic field until later on, life probably couldn’t start until the radiation bombarding the planet could be deflected. Thankfully, Areios regenerates its atmosphere through volcanic venting and it has enough gravity to hold on to some of the gases that would otherwise leak out of an Earth’s sized planet’s atmosphere, so the atmospheric stripping one would expect from Hemera’s solar wind can be kept at bay, or at least mitigated for a while.

This magnetic field reverses from time to time, and we have evidence of this on earth in iron-bearing minerals that have spewed out onto the crust from the mantle. In the Atlantic Ocean, there are areas where new crust is being created; magma from the mantle forces its way onto the surface as lava that cools and forms the ocean floor. As it solidifies, new material pushes the old material out of the way as more lava wells up from the mantle in a process called seafloor spreading. Magnetized iron in mineral crystals from the mantle record which way the magnetic field is spinning at the time when it hardens into rock. These rocks record a trend of increasing or diminishing magnetization of iron in the mantle and they show evidence that over geologic time, the poles will reverse with the North Pole flipping down to the South Pole and vice versa. During the process where the magnetization flips, there are periods of weak magnetization that can be disastrous for life because this causes more ionizing radiation to leak through the atmosphere.

On Areios, the thicker mantle keeps the insides of the planet too hot to differentiate the mantle and core into two distinct layers until later on in Areios’ history. That means that for the earliest period in Hemera’s stellar life cycle, Areios is unprotected by the cosmic rays that Hemera would bring onto Areios’ surface. Only after Hemera stops blasting the surface of Areios with radiation does Areios develop a magnetic field. Four billion years after the formation of Areios, we see a number of habitability factors line up for the first time; Hemera stops having such violent solar flares, the bulk structure of the planet settles down to trigger its magnetic field, the planet’s volcanism shoot out less gas, which causes a geologic ice age period. All of these converging factors lead to the first Areiosan lifeforms, the Areia.

magnetic field

Click here for an animation of the Earth’s magnetic pole reversal by the Pittsburgh Supercomputing Center


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