Scientists carrying out research into the composition of the makeup of the Earth’s liquid core have recently announced that they have some interesting news about the Earth’s core. They are confused because the core isn’t quite composed of what they thought it was.
The majority of the liquid outer core of the planet is, obviously, composed of molten iron. That’s fine for human life on Earth, since the spinning mass of superhot melted metal that we live atop creates an extremely powerful magnetic field that wards off plasma storms and cosmic rays that would keep us from surviving otherwise.
But, traditional scientific theory suggests that there should be some lighter elements thrown into the liquid mix composing the outer core, otherwise it would be a different density. (This density can be analyzed using seismic observations.) Up to this point, specialists in those areas hypothesized that the lighter element mixed in with the iron was probably oxygen, which is the next most abundant element in the world. But it looks as if this is not the case.
How They Discovered It
Maybe disappointingly, scientists didn’t discover this by leading a huge expedition to the Earth’s core, but instead by carrying out relatively boring lab work.
“We can’t sample the core directly, so we have to learn about it through improved laboratory experiments combined with modeling and seismic data,” says Yingwei Fei from the Carnegie Institution.
Fei and his team combined various alloys of iron and lighter elements and then subjected them to conditions of temperature and pressure akin to those present in the outer core, then conducted seismic shockwave tests on them. They haven’t determined what the outer core is composed of, but they can be sure that it’s not an iron-oxygen mix.
“The research revealed a powerful way to decipher the identity of the light elements in the core. Further research should focus on the potential presence of elements such as silicon in the outer core,” notes Fei.
Having such a small amount of oxygen in the outer core indicates that there was far less oxygen when Earth was born.So now it looks like silicon may actually be more important than scientists always thought. The new discoveries have very real implications for the way that we think about the Earth and what we know about how it was formed. Therefore, it also has important applications in how we think about other planets and the ways that they formed.
The study’s results were published earlier this week in Nature. Debates about the core’s chemical composition have been going on for nearly 60 years, notes geophysicist Thomas Duffy from Princeton University. Duffy writes that “the work reported here suggests that a solution to the problem may finally be at hand,” in a commentary accompanying the study’s official report.
Even with the progress of this study, Fei is not done. “I am working on models with different silicon/sulfur ratios,” Fei says. “More experimental data are needed to find the combination that is consistent with both geophysical and geochemical constraints.