I suspect that there exists an objective morality capable of being investigated, but not using the methods commonly known as science.

What we currently think of as objective knowledge comes from one of two methods:

1) Start with self-evident axioms and apply logical rules of inference. The knowledge obtained from this method is called "mathematics".

2) The method commonly called the "scientific method". Note that thanks to the problem of induction the knowledge obtained using this method can never satisfy method 1's criterion for knowledge.

I suspect investigation morality will require a third method, and that the is-ought problem is analogous to the problem of induction in that it will stop moral statements from being scientific (just as scientific statements aren't mathematical) but ultimately won't prevent a reasonably objective investigation of morality.