 Xenon is the preferred propellant for ion propulsion of spacecraft because of its low ionization potential per atomic weight , and its ability to be stored as a liquid at near room temperature ( under high pressure ) yet be easily converted back into a gas to feed the engine . The inert nature of xenon makes it environmentally friendly and less corrosive to an ion engine than other fuels such as mercury or caesium . Xenon was first used for satellite ion engines during the 1970s . It was later employed as a propellant for JPL 's Deep Space 1 probe , Europe 's SMART @-@ 1 spacecraft and for the three ion propulsion engines on NASA 's Dawn Spacecraft . 
 Xenon <a href='drop_aux' title='1'><mark>is</mark></a>the preferred propellant for ion propulsion of spacecraft because of its low ionization potential per atomic weight , and its ability to be stored as a liquid at near room temperature ( under high pressure ) yet be easily converted back into a gas to feed the engine . The inert nature of xenon <a href='uninflect' title='2'><mark>makes</mark></a> it environmentally friendly and less corrosive to an ion engine than other fuels such as mercury or caesium . Xenon was first used for satellite ion engines during the 1970s . It was later employed as a propellant for JPL <a href='null_genetive' title='3'><mark>'s</mark></a>Deep Space 1 probe , Europe <a href='null_genetive' title='4'><mark>'s</mark></a>SMART @-@ 1 spacecraft and for the three ion propulsion engines on NASA <a href='null_genetive' title='5'><mark>'s</mark></a>Dawn Spacecraft . 
Xenon the preferred propellant fir ion propulsion of spacecraft b/c of its low ionization potential per atomic weight , and its ability to b stored as a liquid at near room temperature ( under high pressure ) yet be easily converted back into a gas to feed da engine . Tdainert nature of xenon make it environmentally friendly and less corrosive to an ion engine than other fuels such as mercury or caesium . Xenon was first used fa satellite ion engines during thda970s . It was later employed as a propellant for JPL  Deep Space 1 probe , Europe  SMART @-@ 1 spacecraft and for thedaree ion propulsion engines on NASA  Dawn Spacecraft .