I think I've seen it before. Is it about a kid who finds a little puff-ball alien? When he goes to school in Mars, the school-master(sp?) sees it and wants to steal it and exploit it because that puff-ball alien was very rare and can lead to certain natural resources? At the end of the mini series, that puff-ball alien is all grown up/evolved. There was one scene that I remember quite well. When the kid was trapped inside one of those plants and was running low on oxygen from his damaged space suit, he turned on his flash light and pointed it against the plant wall to simulate the process of photosyhthesis to get oxygen.
Also, IIRC, the mini-series was based on a book. Do all this sound right?