The announcement from NASA that’s coming later today is not about life on Mars, (or Saturn, as the original rumour had it) but is apparently the announcement that NASA has discovered a completely new life form that’s built from arsenic. It has a completely alien DNA than us, and changes what we thought were the necessary building blocks of life.
Everything on the planet shares the same chemical building blocks for life: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulphur. However, the bacteria fished out of the poisonous Mono Lake in California is built from arsenic instead, which everyone thought was impossible. This means that what we thought you needed to make life isn’t actually the case, which in turn has a knock on effect on what we’ve been presuming is required to support life on other planets. In science terms, this is massive.