Return to Earth is based on a game from the 1980's called Gyruss.

In this game you are a space explorer returning to earth, but your path through the solar system is blocked by alien forces and space debris. Shoot the bad guys and pick up the astronauts for extra points.

Control your ship by tilting the phone and tap the screen to fire. Pressing the shield at the bottom will active your space ships shield, but only if available.

You can download it free from the Marketplace here:
http://www.windowsphone.com/en-GB/search?q=return+to+earth