Study finds no magnetic field on Rosetta’s comet - why that matters


The first scientific paper to include observations from the surface of a speeding comet has been released, marking a new era in cometary science.

The paper, published Tuesday in the journal Science, uses data from the European Space Agency’s Philae lander and the Rosetta orbiter to determine whether the nucleus of comet 67P/Churyumov-Gerasimenko has its own magnetic field. Other space missions have tried to measure the magnetic field of comet nuclei in the past, but the results were never conclusive.

To be fair, it is a difficult observation to make. As comets fly toward the sun they begin to heat up, causing formerly frozen gas and dust to spew from vents on the nuclei’s surface. That material interacts with the swiftly moving gas of electrons and ions coming from the sun called solar wind and creates a magnetic envelope around the comet. The magnetized bubble of gas and dust masks the magnetic field of the comet’s nucleus making it difficult to observe, until now.


“No mission before Rosetta was able to come close enough to a comet nucleus to detect its magnetic field unambiguously,” said Christopher Russel a scientist at UCLA and coauthor of the paper. “Landing on the surface of a comet was needed to get close enough to the magnetic material in the comet.”

As it turned out, the researchers did not detect a magnetic field on 67P/Churyumov-Gerasimenko, which is kind of a bummer because it leaves a mystery of planetary formation unsolved.

“People were hoping to detect a magnetic field, and will continue to look for one because it is important,” Russel said.

According to some models, the presence of a magnetic field around most small bodies was necessary for establishing the structure of the early solar system - causing the planets to spin faster in their orbits around the sun, and the sun itself to spin more slowly, Russel said.

The findings here would suggest that something else was going on.

“The result constrains how primordial bodies could have been perturbed (or not) by early solar magnetic fields,” said Matt Taylor, Rosetta project scientist for the European Space Agency.


Cometary scientist Paul Weissman of the Jet Propulsion Laboratory said the findings were not unexpected.

“It tells us that material in the early solar nebula was generally not magnetized,” he said. “It was the expected result, but it is always best to measure things in order to confirm expectations.”

Russel is not so sure.

“This is significant, but it is only one comet born in one place and time,” he said. “Perhaps other comets around in the early system were magnetized.”

He adds: “Maybe we will find a magnetic field on the next cometary nucleus we visit.”

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