I saw that there is an alternative ending for Waking Mars. What do I need to do differently during the course of the game to get it? I haven't found a particularly good guide online.
Once you've seen the first ending, you should be able to simply reload your save and try to get the alternate endings.
In the Helm, there are two platforms. The one on the right was the one you (presumably) used to get the regular ending. Don't active it, but use the left platform instead; if you have enough biomass you can trigger the second and third ending by standing in front of the statue. After the ship takes off, you can either leave the room (to get one alternate ending) or stay there (to get the other).
If you don't have enough biomass/core power, you need to get more before you can get the alternate endings.
The sentients on top of the Helm should direct you back to the Power Station. Follow their instructions.