In each of the regular missions, you'll find three alien artifacts hidden throughout the level. Collect all three and complete the regular mission, and you'll unlock a bonus challenge.
|Unlockable||How to unlock|
|Bonus Mission Challenges ||Collect all three alien artifacts in a regular mission, then complete the mission.|
Verified by: this cheat is unverified
Submitted by: Eridor
on May 18, 2009