Mercury's Ion Spectrum (Graph)

Image Credit: NASA / JHUAPL / U. Michigan

Original caption:

MESSENGER's Fast Imaging Plasma Spectrometer (FIPS) scoops up ions from Mercury's exosphere and measures their composition as a ratio of their mass to their charge. Each atomic or molecular ion shows up as a distinct peak in this spectrum. Most ions are singly charged (missing one or having one extra electron) so are visible as a peak at the atomic mass of the element (for example, sodium at 23). A few are present as multiply charged ions, for instance doubly chaged oxygen at a peak of 8. The surprising result is the detection of water-related ions like O+, OH-, and H2O+.

(MESSENGER Scientists 'Astonished' to Find Water in Mercury's Thin Atmosphere!)

http://www.planetary.org/news/2008/0703_MESSENGER_Scientists_Astonished_to.html

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