Currently, the Marvel Cinematic Universe is setting up Thanos for later films, a mad Titan who is supremely powerful thanks to the Infinity Gauntlet, a device worn on the hand that is powered by 6 Infinity Stones or Infinity Gems.

In the comics, these are listed as;

the Power Gem , which increases the user's physical power,

, which increases the user's physical power, the Mind Gem , which increases the user's psychic and mental abilities,

, which increases the user's psychic and mental abilities, the Soul Gem , which allows the user to control the free will of others,

, which allows the user to control the free will of others, the Space Gem , which allows the user to travel through space,

, which allows the user to travel through space, the Time Gem , which gives the user control over time, and

, which gives the user control over time, and the Reality Gem, which gives the user total control of reality.

So far, we have seen 4 of these stones in the MCU, in varying forms.

Very mild spoilers for The Avengers/Avengers Assemble, Thor: The Dark World and Guardians of the Galaxy below.

In The Avengers/Avengers Assemble we see the Tesseract is the Space Gem and that Loki's Staff contains what could soon turn out to be either the Mind Gem or the Soul Gem (This was later confirmed to be the Mind Gem in Avengers: Age of Ultron)

In Thor: The Dark World we see that the Aether is one of the Infinity Stones

In Guardians of the Galaxy we see that the mysterious orb contains one of the Infinity Stones. However, both the Purple Infinity Gem seen in Guardians of the Galaxy and the Aether in Thor: The Dark World appear to fulfill the role of the Power Gem.

So my question is - which of these items in the films match the Gem in question, and what is the function of the other?