Obviously the scientist, alien, robot and I will have to live, since we seem to be the only ones on board with any useful defining characteristics. It's either the hot guy/girl or the minority whom I'll boot out.
But if they all had equal qualifications...the robot, scientist, alien (especially), and I would still need to live. Though...as much as I love robots, I value human life more than robotic imitation. However, I think adding the robot makes this choice way too easy.
So, disregarding the robot, if I had to pick someone else, I'd...make sure the scientist stayed, because they'd need him. And the alien would have to stay too, because...well, it's an alien. And that's boss. That leaves the hot person, the minority and I, and as much as I'd love not dying, I think I'd actually prefer dying on a different planet as opposed to just on Earth. If I really liked the other two people, and wasn't looking forward to anything in my future, hell yeah I'd go. But if they were jerks, I'd assure that one of them was the one to go.
And now I just have to wonder why on Earth we'd build a machine to go to a different toxic planet without any way of collecting specimens that didn't involve a sacrifice.