The histogram in this figure represents a typical MASCS observation in the
tail region of Mercury’s exosphere from magnesium atoms. These MASCS
measurements mark the first time that magnesium has been detected in
Mercury’s exosphere. In contrast to emissions from sodium and calcium (see
PIA11402), magnesium emission occurs at a wavelength that is in the ultraviolet
part of the spectrum. Magnesium has not been observed from ground-based
telescopes partly because it emits at ultraviolet wavelengths, which are
completely obscured by Earth’s atmosphere. Because these atoms primarily
originate at the surface of Mercury, the detection of magnesium in the
exosphere provides evidence that magnesium is a component of surface
material, something that has been expected for years but until now had not
been proven. As with calcium and sodium, the distribution of magnesium
in Mercury’s exosphere is a result of the processes that release the
magnesium atoms from the surface and can provide valuable clues to the
relative importance of each process.
Date Acquired: 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.
