A Russian rocket put a trio of European science satellites into orbit around Earth’s poles on Friday for a four-year mission to map the planet’s magnetic field and learn more about why the protective shield appears to be weakening.

The $280 million mission, called Swarm, is the first to map the sources and strengths of Earth’s magnetic field, an invisible bubble that protects the planet from deadly solar and cosmic radiation.

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Mars once had a magnetic field and its disappearance billions of years ago is believed to be the primary reason why the planet lost its atmosphere and turned into a cold, dry desert.

The main generator of Earth’s magnetic field lies deep in the planet’s core where flowing super-hot liquid iron creates electrical currents that in turn produce magnetic fields, a process known as a “dynamo.”

The fields extend for thousands of miles into space, creating a bubble, known as the magnetosphere, that deflects potentially dangerous charged particles streaming from the sun and cosmic sources.

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There is some evidence that Earth’s magnetic field is weakening, a sign perhaps that the field is preparing to flip. Geologic records show that happens on average about every 250,000 years, but the last time Earth’s magnetic field flipped was about 800,000 years ago.

“We really need to go what’s going on because it does have an impact on life,” mission manager Rune Floberghagen said in an European Space Agency interview.

“It has an impact on the behavior of animals. It has an impact on navigation systems. It has an impact on a lot of things, practical things to all of us, not only scientists who would like to understand the Earth itself,” he said.

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Swarm is designed to ferret out the different sources of Earth’s magnetism as well as study currents in the planet’s ionosphere that can interfere with the magnetic field coming from the core.

“Swarm is about to fill a gap in our view of the Earth system and in our monitoring of global change issues,” Volker Liebig, ESA’s director for Earth observation, said in a statement.

Image: Artist’s rendering of Earth’s complex magnetic and electrical fields. The three Swarm satellites are designed to track their sources. Credit: European Space Agency