An artist's concept of Mercury's surprisingly active magnetosphere.
During a flyby in 2008, NASA's MESSENGER spacecraft revealed that the planet's atmosphere, magnetosphere and its geological past display greater levels of activity than scientists first suspected.
The magnetosphere is a region of space around Mercury enveloped by the planet's magnetic field. Gusty solar wind buffeting the global bubble of magnetism can potentially trigger magnetic storms and other space weather-related phenomena.
"During the first flyby, MESSENGER measured relatively calm dipole-like magnetic fields close to the planet. Scientists didn't detect any dynamic features other than some Kelvin-Helmholtz waves," said James Slavin of NASA's Goddard Space Flight Center. Slavin is a mission co-investigator.
"But the second flyby was a totally different situation," he says. MESSENGER observed a highly dynamic magnetosphere with "magnetic reconnection" events taking place at a rate 10 times greater than what is observed at Earth during its most active intervals. "The high rate of solar wind energy input was evident in the great amplitude of the plasma waves and the large magnetic structures measured by the spacecraft's magnetometer throughout the encounter."
(Image reproduced courtesy of Science/AAAS)
Last Update: 22 Jun 2011 (AMB)
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/GSFC