A violent tail
Mercury surprises with powerful magnetic storms, signs of volcanism
By Ron Cowen
The solar system’s innermost planet is even more mercurial than planetary scientists had thought, a trio of reports posted online July 15 in Science reveals.
When NASA’s MESSENGER spacecraft flew past Mercury for the third time in September 2009, it found evidence that magnetic storms are much more intense and rapid-fire there than on Earth.
One of the Science articles also provides new details about findings from the flyby, first announced last November, that suggest Mercury was volcanically active much more recently — as little as 1 billion years ago — than researchers had previously thought.
The September MESSENGER flyby is the first time scientists have documented the buildup of magnetic energy in Mercury’s magnetotail, the magnetic lines of force that form a region shaped like a comet’s tail on the planet’s night side. The magnetotail absorbed 10 times more magnetic energy from the sun than Earth’s magnetotail does. It then dumped that energy in just two to three minutes, compared to two to three hours for Earth’s field, report James Slavin of NASA’s Goddard Space Flight Center in Greenbelt, Md., and his colleagues.