Well, calling it a "spring" may be a bit of an exaggeration...

The gullies they've noticed have probably only had flowing water once in the last decade -- and probably not for a *long* time before the last decade. After all, they're noticeable specifically because they're different from the pictures we took ten years ago. Most likely scenario is that there's a block of subsurface ice that has melted for some reason... so it's not quite liquid water under the surface, and it's only liquid for a very brief period before it either freezes or boils.

Still very cool stuff, though. :)