Click on the image for movie of
MESSENGER Flies through Mercury's Magnetosphere
This animation shows a conceptual sketch of Mercury's magnetosphere at
the time of the MESSENGER flyby. The graphs at the bottom show
observations made by the Fast Imaging Plasma Spectrometer (FIPS) portion
of the Energetic Particle and Plasma Spectrometer (EPPS) instrument as the
spacecraft followed the indicated trajectory. The top plot depicts the
low-energy plasma of solar wind origin, and the bottom plot shows heavy
ion intensities associated with the planet. This flyby was the first
survey of the ion plasma of Mercury's space environment. The positions at
which the spacecraft first crossed the "bow shock" of the magnetospheric
interaction with the solar wind, passed closest approach to the planet,
and crossed the outbound bow-shock crossing are indicated.
These results show the expected increases in solar wind plasma density
downstream of the bow-shock boundary, as well as significant solar wind
plasma densities within Mercury's magnetosphere close to the planet. The
latter measurements provide definitive evidence that Mercury's
magnetosphere—despite its small size—is not a vacuum but hosts
significant densities of heated solar wind plasma. The plasma affects the
magnetic field, contributes to the "space weathering" of the planet's
surface, and sputters material from the surface to populate the exosphere.
This first detection of heavy pick-up ions, Na+ and other species, near
Mercury is consistent with their production by ionization of exospheric
neutral species. This complex system and all of its time variations will
be studied during the next two MESSENGER flybys as well as throughout the
orbital phase of the mission.
These images are from MESSENGER, a NASA Discovery mission to conduct the
first orbital study of the innermost planet, Mercury. For information
regarding the use of images, see the MESSENGER image use policy.
