So, before the actual NASA press conference, word got out about the research paper that was published which detailed the existence of bacteria which used arsenic in its basic metabolism and genes. This bacteria was found on Earth, in California's Mono Lake. The interesting thing about this is that up until this discovery, it was thought that life needed hydrogen, carbon, phosphorous, nitrogen, oxygen and sulfur to survive and thrive. Arsenic, a very poisonous substance, was considered detrimental to the existence of life. Now, our basic understanding of the requirements for life to exist has fundamentally changed.
I think a lot of people were greatly disappointed in today's announcement. Many were probably anticipating the receipt of an alien radio signal, or the observance or detection of an alien life form somewhere, maybe on Mars or Titan, even in the form of microbiological life. Many news websites had posted bold questions on their main sections to the effect of "What will NASA Announce?" coupled with pictures of E.T. or "gray" alien faces. No wonder folks got excited!
I think this is still a very valuable discovery. It shows that life is versatile and resilient, and can exist in many places we previously would not even begin to think to search. As we discover more and more exoplanets and take a closer look at the planets and moons within our own Solar System, we are now faced with the prospect, however daunting, that if bacteria can survive in an environment previously considered hostile to life itself, that life can exist in a multitude of environments that we had not yet considered.
While it makes the search for extraterrestrial life harder because we now have to rethink how we view life itself, it vastly increases the potential for the existence of alien life, in whatever form, throughout the universe.