Detection of lithium in the exosphere of Mercury.

Mercury's exosphere contains various neutral species, including hydrogen, helium, sodium, potassium, calcium, magnesium, aluminum, iron, and manganese. Although lithium has been predicted to exist, it had not been detected until now. Here, we demonstrate the presence of lithium in Mercury's exosphere, using data from the Mercury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft.