Mariner 10 radiation. The plasma experiment's goal was to study the ionized gases (plasma) of the solar wind, the temperature and density of its electrons, and how the planets affected the velocity of the plasma stream. The experiment contained two components, facing in opposite directions. The Scanning Electrostatic Analyzer was aimed toward the Sun, and could detect positive ions and electrons, which were separated by a set of three concentric hemispherical plates. The Scanning Electron Spectrometer was aimed away from the Sun, and detected only electrons, using just one hemispherical plate. The instruments could be rotated about 60 degrees to either side.
Plasma (physics) first used the word "plasma" in analogy with blood. Mott-Smith recalls, in particular, that the transport of electrons from thermionic filaments reminded Langmuir of "the way blood plasma carries red and white corpuscles and germs." Langmuir described the plasma he observed as follows: Plasma is a state of matter in which an ionised gaseous substance becomes highly electrically conductive to the point that long-range electric and magnetic fields dominate the behaviour of the matter. The plasma state can be contrasted with the other states: solid, liquid, and gas. Plasma is an electrically neutral medium of unbound positive and negative particles