At https://phys.org/print411059802.html … it seems that NASAs MAVEN spacecraft has detected metal ions in the atmosphere of Mars – which shows that the ionosphere of Mars is electrically charged. MAVEN is exploring the atmosphere of Mars for clues as to why it is so thin (in comparison to the Earth and Venus). It is assumed it once had a more dense atmosphere – which has been lost.
The metal comes from a constant rain of tiny meteoroids from outer space. So far MAVEN has detected iron, magnesium, and sodium ions using a mass spectrometer. Metal ions were also detected during the close passage of Comet Siding Spring back in 2014. Sounding rockets, radar and satellite measurements have also detected metal ions high in the atmosphere of the Earth.