Magnetic Twisters "Dance" Across Mercury, Study Says

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(Related: "Giant 'Space Tornadoes' Spark Auroras on Earth.")

What surprised scientists is that reconnection on Mercury is ten times more intense than it is on Earth, said study author James Slavin of the NASA Goddard Space Flight in Greenbelt, Maryland.

It's reasonable to think that magnetic reconnection would be stronger on Mercury, the closest planet to the sun. But researchers were anticipating it would only be about two or three times more intense than on Earth, Slavin said.

Figuring out why the process is so much stronger than expected could shed light on how solar wind affects magnetic fields around other planets, including Earth.

Despite the stronger reconnection events, Slavin said, "at Mercury, we don't have an atmosphere that's dense enough or of the right kind of gas probably to produce anything we would recognize as auroras."

Still, similar invisible currents may exist along those same magnetic regions of Mercury.

"It's possible there may be a little ring around both poles of Mercury, where the surface is ever so slightly warmer than the other latitudes of the planet," Slavin said. (See a photo of "hyper auroras" on Jupiter.)

Solar Erosion

The new observations also show that—like the twisters—the solar wind directly plays a part in shaping the mysterious planet's surface.

Earth, Jupiter, and Saturn have dense atmospheres and strong magnetic shields, protections that deflect the full force of the winds from reaching their surfaces.

On Venus and Mars, meanwhile, there're little or no magnetic fields but some atmospheres, so "there's a tendency for the solar wind to strip away the atmosphere over the eons," Slavin said.

(Related: "Stars Can Strip Gas Giants Naked.")

"In the case of a body like Mercury, where you don't have a planetary atmosphere, or you have an extremely tenuous one, you have a situation where the solar wind … actually erodes the surface somewhat. It's a very small amount," Slavin said.

Sean Solomon of the Carnegie Institution in Washington, D.C., who was involved in the research, noted that there was much more magnetic activity during the October flyby than during MESSENGER's first encounter in January 2008. (See photos from the first Mercury flyby.)

"Mercury is a lot more complicated and its processes are a lot more dynamic than we knew," Solomon said.

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