Galactic Adventures will allow you to completely customise the planets that will play home to your adventures. You'll be able to change the colour of their terrain, water, sky and atmosphere, ... alter the temperature and create continents, before populating them with your choice of assets from the millions that Sporepedia houses.
Hang on a minute, it will let us change the colour of the terrain, like we already can. It will let us change the colour of the water, like we already can. It will let us change the colour of the sky, like we already can. It will let us change the colour of the atmosphere, seriously wtf? isn't that just another way of saying you can change the colour of the sky. It will let us change the temperature you mean like the way I already spent many joyless hours doing just to let me colonise a new planet. Create continents you mean like the way we already can. And populating them with our choice of assets just like we already could. Sounds to me like they fiddled around with a few numbers and called it new content, not that I expected anything else.
I'm pretty sure they mean to say that you can do all this via the Adventure Creator. As in, scripted. So you can have an adventure that includes the world being flooded, or heated to magmanic proportions. After that we can put any pieces and buildings and critters from the Sporepedia on them any way we like, and give them dialogue, behaviour and actions. Then other people could land on the planet and encounter the "scene" we set up, trying to finish it as soon as possible, or with the best score.
From what I've read in the article I linked to earlier, making a DF-like planet would be entirely possible. We could make dwarf-like critters and stuff them in a fortress made from various pieces, complete with "flood the world" lever. Heh, we could promote DF this way by introducing the game to the players.
Of course, you could do all that already from inside your spaceship, it's just some different numbers, that's all. No new content, no sir. Not a bit!