After reading some of the answers here, and further Google (re)searching, I came to the following:
There are two parts to wielding Mjolnir.
Wielding Mjolnir (possessing Thor's power)
Before wielding Mjolnir, it needs to be lifted. As portrayed in much of the modern comics and movies, unless you are worthy, the hammer won't budge from where it is (Excluding the axe/hammer version of Mjolnir). But in most cases, there is gravity in place. When there is zero gravity, it can be moved.
Two examples of this:
Ironman and Red Hulk are two characters that encountered Mjolnir in outer space, and were able to move, grasp, and even use it on Thor.
Ironman encounters Mjolnir in space, grabs it, and moves it.
Upon entering Earth's atmosphere, gravity pulls Mjolnir towards the ground, and Ironman can no longer move it.
Red Hulk is able to swing Mjolnir in space. Although there may have been a loophole also that Rulk actually took possession of the hammer from Thor.
However, being able to lift or move Mjolnir doesn't equate to being worthy nor is the same as wielding it. The inscription on the hammer states: Whosoever holds this hammer, if he be worthy, shall possess the power of Thor.
It doesn't say that it cannot be lifted. It states that it be held AND if is worthy, shall possess the power of Thor. So we can interpret Odin's enchantment to generally apply to those that lift it and are worthy. For the cases when it can't be lifted, it is a side effect when gravity is present.
So, in short, yes it can be moved in outer space, but not wielded.
The worthy can lift and wield it. The unworthy cannot lift it when gravity is present, but they can move it absent a gravitational pull. They also cannot wield it nor possess the power of Thor.