Rosetta mission finds comet has no magnetic field

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The European Space Agency (ESA) has revealed through analysis of data sent across by Philae lander and Rosetta orbiter that its target comet, 67P/Churyumov-Gerasimenko, has no magnetic field.

Measurements made by Rosetta and Philae during the probe’s multiple landings on Comet showed that the comet’s nucleus is not magnetised.

Hans-Ulrich Auster, co-principal investigator of ROMAP and lead author of the results published in the journal Science, said that the findings could sweep away a key theory on the formation of comets and other solar system bodies.

“If the surface was magnetised, we would have expected to see a clear increase in the magnetic field readings as we got closer and closer to the surface,” explains Hans-Ulrich. “But this was not the case at any of the locations we visited, so we conclude that Comet 67P/Churyumov-Gerasimenko is a remarkably non-magnetic object.”

It could mean that magnetic forces may not have played a role, as theorised by some, in a crucial stage of planet building.

The magnetic field measurements from Rosetta and Philae also showed details about how the lander bounced twice high off the surface of the comet and then rolled before settling in what was thought to be the edge of a shady crater.

But it remains unclear as to how crucial magnetic fields were later on in this accretion process, as the building blocks grew to centimetres, metres and then tens of metres across, before gravity started to dominate when they grew to hundreds of metres and kilometres in scale.

“If any material is magnetised, it must be on a scale of less than one metre, below the spatial resolution of our measurements. And if Comet 67P/Churyumov-Gerasimenko is representative of all cometary nuclei, then we suggest that magnetic forces are unlikely to have played a role in the accumulation of planetary building blocks greater than one metre in size,” concludes Hans-Ulrich.

The study is published in the journal Science.