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Mercury's sodium and hydrogen tails

Mercury's sodium and hydrogen tails
Mercury's sodium and hydrogen tails MESSENGER's ultraviolet and visible spectrometer, part of the MASCS instrument, mapped the tail of Mercury as the spacecraft approached for its first flyby of the planet. The plots show the intensity of the emission of certain wavelengths of light, which is related to the abundance of neutral atoms in Mercury's exosphere. The upper plot shows the intensity of light at 589 nanometers, the orange color familiar from sodium lamps used widely in street lights. The intense emission of sodium atoms at this wavelength makes them very easy to detect. The lower plot shows the intensity of light at the Lyman-alpha emission of hydrogen, at a far ultraviolet wavelength of 121.6 nanometers. NASA / JHUAPL / CIW