Sierra 117

Landfall is believed to be the first campaign mission of Halo 3.

It takes place in a jungle.

It was likely named because SPARTAN-117 disembarks from the Forerunner Ship onto the lands of Earth, although this is unconfirmed.

This is unlikely, however, because the comic series Halo: Uprising takes place after the ending of Halo 2.

Upon completing it on the Normal, Heroic, or Legendary difficulties, the player will earn the "Landfall" achievement and 20 Gamerpoints.