What just happened? NASA this week said its Juno spacecraft has uncovered evidence suggesting Jupiter has an internal magnetic field that changes over time, much like Earth’s. The phenomenon, known as secular variation, is most likely caused by the planet’s deep atmospheric winds, the agency said.

Juno launched from Cape Canaveral in August 2011 as part of the New Frontiers program and entered a polar orbit around Jupiter in July 2016. The craft was sent to study Jupiter’s magnetic field, gravity field, composition and polar magnetosphere.

NASA used data collected during Juno’s first eight passes of Jupiter to create a three-dimensional map of the planet’s magnetic field. This map was then compared to data collected from past missions, some dating back more than four decades. What they noticed were small but distinct changes to Jupiter’s magnetic field.

“Having a baseline of close-up observations over four decades long provided us with just enough data to confirm that Jupiter's magnetic field does indeed change over time,” said Kimee Moore, a Juno scientist from Harvard University in Cambridge, Massachusetts.

Scientists think atmospheric winds are responsible for changes in the planet’s magnetic fields. The winds extend from the surface to over 1,860 miles deep where the planet’s interior starts to change from gas to highly conductive liquid metal. It is believed that these winds shear the magnetic fields, stretching and carrying them around the planet.

The discovery will help scientists better understand the many mysteries of Jupiter and could even help unlock some of the remaining secrets of Earth’s magnetic field.

Image credit: Solar System Jupiter by NASA images