Rare Earth: our protective magnetic field (Introduction)

by David Turell , Thursday, June 02, 2016, 02:43 (2879 days ago) @ David Turell

There are two iron layers in the core of Earth. the outer one creates the magnetic field with its movement:-http://phys.org/news/2016-06-sustains-earth-magnetic-field.html-"Earth's magnetic field shields us from deadly cosmic radiation, and without it, life as we know it could not exist here. The motion of liquid iron in the planet's outer core, a phenomenon called a "geodynamo," generates the field. But how it was first created and then sustained throughout Earth's history has remained a mystery to scientists.-*** -"Our planet accreted from rocky material that surrounded our Sun in its youth, and over time the most-dense stuff, iron, sank inward, creating the layers that we know exist today—core, mantle, and crust. Currently, the inner core is solid iron, with some other materials that were dragged along down during this layering process. The outer core is a liquid iron alloy, and its motion gives rise to the magnetic field.-***-"The team used a tool called a laser-heated diamond anvil cell to mimic planetary core conditions and study how iron conducts heat under them. The diamond anvil cell squeezes tiny samples of material in between two diamonds, creating the extreme pressures of the deep Earth in the lab. The laser heats the materials to the necessary core temperatures.-"Using this kind of lab-based mimicry, the team was able to look at samples of iron across temperatures and pressures that would be found inside planets ranging in size from Mercury to Earth—345,000 to 1.3 million times normal atmospheric pressure and 2,400 to 4,900 degrees Fahrenheit—and study how they propagate heat.-"They found that the ability of these iron samples to transmit heat matched with the lower end of previous estimates of thermal conductivity in Earth's core—between 18 and 44 watts per meter per kelvin, in the units scientists use to measure such things. This translates to predictions that the energy necessary to sustain the geodynamo has been available since very early in the history of Earth.-"'In order to better understand core heat conductivity, we will next need to tackle how the non-iron materials that went along for the ride when iron sunk to the core affect these thermal processes inside of our planet," Goncharov added."-Comment: Part of the fine tuning that led to life. Nickel is one of the other components of the core.