Feros is the planet that has the colonists and is not covered in snow. Now, all you have to do is: Talk with the leader, kill the Geth, now this is important: Talk with him again, then talk with the people in charge of: Food, water, and power, and do their side quests! After that, move up the bridge, go to ExoGeni, find Lizbeth, return to the colony. Now, either upgrade your grenades with the Thorian gas or kill them all. Now, if you kill them and didn't do the side quests, you will NEVER complete them.