Advisor wants me to break our group out into a different area
I don't see it as very unusual. The advisor seems to want to have several projects going at once to maximize the chance of success on at least some of them. It is common, where I've been, for different students to work on different things. 

But as you go along, you will need continuing guidance. Setting a simple expectation at the start (write a paper) is probably fine as long as it doesn't end there. And you will also need to depend on the ability of the advisor, and his general experience, to get you over any hard spots or know when it is time to move to a different problem if the chosen one turns out to be fruitless. 

It actually sounds like he has some faith in you to carry on. That can turn out to be a great thing. 

And, as you go, keep notes on other directions that your work suggests might be good to explore in the future. Having lots of "irons in the fire" is a good way to avoid getting stuck.