From BoardgameNews.com:

Spiel '08 will see a new truckload of interstellar destruction with Galaxy Trucker: The Big Expansion. As is often the case with expansions, The Big Expansion includes a number of mix-and-match components:

• Pieces and rules for five-player games.
• An updated version of Rough Road Ahead, a set of cards previously released in a downloadable format on the Czech Games website that will be expanded and reformatted.
• Additional adventure cards, including two previously available only at Spiel 07.
• A special deck of adventure cards that players individually insert into the deck themselves to surprise their fellow drivers.
• A new alien species.
• New ship building components, including life support for the new ET.
• New ship classes.

The expansion is not fully compatible with the first edition of Galaxy Trucker, due to component differences. A compatibility kit has been produced, containing replacement components for the base game, but as of March 2009 it is not yet widely available.