First there was the astonishing revelation that whole ecosystems exist around volcanic 'black smokers' on the seabed that derive all of their energy from chemicals rather than from the Sun. That was a surprise. Then there are the extremophiles we've discovered; microorganisms that can exist in environments thought to be entirley hostile such as inside rock, in molten lava, frozen in supercold ice or even in space. And just a few months ago (see here) creatures called loriciferans were found living below the Greek seabed that don't need oxygen at all - another first.
And now we've found a creature that doesn't conform to our understanding of what the building blocks of life should be. All life on Earth is made of six components: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulphur. Everything from an amoeba to a blue whale has the same basic structure. But not this bacterium. Discovered in the poisonous waters of Mono Lake, California, it uses arsenic instead of phosphorous, something that was thought to be completely impossible. The implications of this discovery are enormous.
It means that life on other worlds could be even more bizarre than we could possibly imagine. Take that astrobiologists.