It’s getting close to two years now since a NASA-funded team of scientists announced they had found a form of life that broke all the rules by using arsenic to build its DNA. It’s become something of an obsession for me. If you want to follow the saga, click here and start back at the earliest post. In July I live-blogged the announcement that other scientists had replicated the experiment and failed to find the same results. In some ways, that was the logical end to the story

My fascination with this story has been tempered from the start by a creepy feeling. As a science writer, I most enjoy reporting on advances in biology: the research that opens