Earth’s magnetic mystery forces scientists to get creative

Put it in the category of invisible but vital: The magnetic field that envelops the Earth shields life from harmful ions spat out by the sun. Although unseen, it’s not undetectable (try a compass); auroras displayed when geomagnetic storms hit the polar regions hint at its presence. Our magnetic field has protected us for eons, its existence recorded in minute crystals hidden in ancient rocks.

Scientists believe that this magnetic field originates in the roiling of iron and dancing of electrons within the metallic soup of the Earth’s core. But exactly how that magnetism mechanism works has been a hard question to answer. From decades of study, geophysicists have pieced together a general picture of the process: The cooling of the planet’s solid inner core stirs up the liquid iron in the outer core. This movement creates electric currents, which generate magnetic fields.

But that explanation hinges on how that metallic fluid motion, called convection, is powered. Some recent computer simulations, as Thomas Sumner reports, suggest that the early Earth could have powered only a weak magnetic field. Yet the rock record suggests a strong field, as would have been needed to protect early life. This paradox has led scientists to perform new experiments, probing the nature of iron at high temperatures and pressures, along with continuing simulations of how matter ought to behave deep in the Earth.

It’s a nice example of the excitement that animates scientists when the pieces don’t all fit: They have to rethink things and ask whether they are solving the right puzzle. That can inspire creative approaches, and eventually, new answers.

That’s similar to the story behind results described by Tina Hesman Saey. A gene closely linked to obesity risk does not actually affect fat storage. But a bit of DNA stuck into this gene does. Scientists discovered that this DNA region regulates the activity of two other distant genes involved in determining whether cells develop into energy-storing white fat cells or energy-burning beige fat cells. Asking how the “fat gene” worked turned out to be the wrong question. Maybe in explaining the Earth’s magnetic field paradox, scientists will discover a new question with an even more interesting answer.