This figure shows a comparison of images of the sodium emission in the tail region of Mercury during MESSENGER’s first and second Mercury flybys. The sodium emission was less symmetric during flyby 1 (see PIA11076), with a larger region of emission in the north relative to the south, in contrast to the pattern of sodium emission observed during flyby 2 (see PIA11402). During the orbital phase of the mission, the MASCS instrument will regularly measure emissions from atoms and molecules. Mapping the distributions of species on a daily basis, in conjunction with the information provided by the other instruments on MESSENGER, will constrain the processes that generate and maintain the exosphere as well as provide information on the composition of the surface from which the exospheric species originate.

Date Acquired: January 14 and October 6, 2008
Instrument: Mercury Atmospheric and Surface Composition Spectrometer (MASCS)

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.