The discovery that there are bacteria around deep-ocean thermal vents that make a living by photosynthesis is a wonderful insight into how supremely adaptive life can be, and also, as Carl Zimmer points out, how doggedly determined scientists can be. Cindy Lee Van Dover has been looking for this effect for years. Finally she and her colleagues have found it. The number of cool things microbes can do rises further still.
It's possible, though I don't think it's very likely, that this might offer some insights into the origin of photosynthesis. Van Dover and my friend Euan Nisbet have argued that on the early earth the photons that mattered most to life were the photons that came from such geothermal sources. They were important not because of the energy they carried, but because they indicated where and how far away the sources were. This was an evolutionary inducement to the development of some sort of pigment-based light sensitivity, because such sensitivity whould have made it easier for microbes to find suitable niches around the sea-floor hot-spots on which they depended for chemical energy. Descendants of these deep-vent bugs that found themselves in shallow, sunlit waters might then have evolved ways of using this light-sensing pigment system as a way to harvest the energy of the far more abundant solar photons they were drenched in. According to this account, the photosynthesisers round vents today would be descendants of solar photosynthesisers who later moved back into the ancestral near-darkness. As such, the amount of insight they offer into the origins of photosynthesis may be no greater than that of many other families of photosynthesisers.
People are already speculating about possible astrobiological implications. If bugs can photosynthesise around deep sea vents on earth, why not elsewhere -- for example, on Europa? I suppose there's no obvious reason why they can't, but it seems unlikely to make much of a difference. These bacteria, fascinating as they are, are very unlikely to make up much of the biomass round a vent. (I don't have a full copy of the article; when I can get one I'll check what it says on the matter). Most of the biomass around vents depends on chemistry for growth; these vents kick out lots of hot chemicals which aren't in equilibrium with the surrounding environment, and for lots of microbes that means food. I can't think of any way that an alien environment could offer geothermal light in an environment where it wasn't supplying a lot more energy in some other form. (Doesn't mean there isn't such a way, just that I can't think of one.)
If that's right, this doesn't provide a new energy source for life anywhere where we wouldn't already expect one; it provides a small bonus in places that would already be good canidates. And it's not a bonus we should necessarily expect life in an ice-covered ocean like Europa's to be able to take advantage of anyway. After all, the simplest theory linking deep sea vents to the origins of photosynthesis on the earth requires the creatures which evolved light sensitivity in the depths to migrate to the shallows, where there is far more light, before becoming proper photosynthesisers. Under a thick icecap this would not be possible.
So I don't think this wonderful discovery has much of an effect on the possibilities for life elsewhere. Just shows how fully a big, well developed biosphere like ours can work itself into every ecological nook and cranny that the planet offers. And it retrospectively validates a throwaway claim in Mapping Mars (currently very cheap on Amazon, FWIW) that such photosynthesisers had already been discovered, a claim based on half-remembered accounts of earlier work which had shown that there might be light enough around earthly vents for photosynthesis to be a theoretical possibility. I should have checked my recollections more thoroughly at the time, but somehow I didn't. So for a few years I've been wrong, and now I turn out to have been right. Right by mistake isn't a particularly good way to be right. But it's often a bit better than wrong.