The Mark 39 (XXXIX), also known by it's name as the "Gemini", is a Sub-Orbital suit and is one of the many newly built suits created by Tony Stark, sometime after the events of The Avengers.
It was featured in the movie Iron Man 3, and makes it's debut in the movie when Tony ordered J.A.R.V.I.S. to initiate the "House Party Protocol" in which it was activated along with all the other suits to help him in his fight against Aldrich Killian.
The suit earned it's name the "Gemini", for having the ability to go for minimal space travel and for venturing into space temporarily, as it is derived from it's name. It was built with an armor that could stand the cold temperature and radiation in space and was built in with an oxygen tank to allow Tony to be able to breathe while he was in space.Iron Man Wiki
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