Plasmas come in many varieties depending on their temperature and density. There are often so few plasma particles (ions and electrons) in a volume of space (thus the number density, particles per unit volume, is low) that a spacecraft could fly right through them without damage – even though the temperature of the plasma is thousands of degrees. However, really high energy charged particles can damage spacecraft. The graphic above (temperature vs. number density) shows some of the many forms a plasma can take (both natural and manmade). Making Plasma Think of water – when it’s frozen, it’s a solid. When it melts, it’s a liquid. Heat it and it turns into a vapor or gas. If you heat it even more – to around 1,500°F – water becomes a plasma. Plasma is made up of atoms Atoms are so tiny that more than a million can fit across the head of a pin. They are composed of one or more negatively charged electrons that orbit a positively charged nucleus (made up of neutral particles, called neutrons, and positively charged particles, called protons). Atoms are electrically neutral; they have the same number of positive and negative electrical charges. When gases are exposed to enough heat or other radiation, their electrically neutral atoms split into positively charged fragments called ions and negatively charged free electrons. Another term for plasma is "ionized gas". Because plasma consists of electrically charged particles, it acts very differently from ordinary forms of gas. Neutral atoms behave the way they do because of collisions. Plasmas, on the other hand, are influenced by electric and magnetic fields. Some plasmas (Earth’s ionosphere, for example) are also influenced by collisions but most are not.