The alien machine is activated by Quaid (Arnold Schwarnegger), creating a permanent breathable atmosphere on Mars
...it is also possible that the entire adventure is part of Quaid's Rekall experience (a technician is programming a "blue sky on Mars" as Quaid is being strapped into the Rekall machine).
(Links open in new window)
Read more about this film at The Internet Movie Database.
Read a draft of the script on-line
Buy it on VHS or DVD at Amazon.com.