one will go in the vent the other is dead, take it.

Problem Getting Past The Dead Alien
There is another way to get past the dead alien in the secret room.
Go back to where the force field is and go past it. Open the door at
EXIT SAS 9 then open the big door and go down the corriders until you
reach the fourth big door. Stop at the door and turn around use the
x-scanner on the floor it will open a elevator that will take you to a
secret room past the dead alien body.

Alien Cave
Go to the second level down the stairs in the under zone. Walk in the second
level door, on the top left corner of the screen your cursors will look, then
click. Now use the alien body then use the cable you will now climb down to
the alien cave. This is the way out of the alien maze cave.
F F L F F F R R F L F F L F R F L R F R F
After you get out of the cave take the blue key card off the table (this will
unlock the door in the corridor were the lab is). then have Lora take the
hand off the dead body (this will give you access to the truck).
The truck will take you to a docking bay.
THE END OF THE GAME