> but we don’t understand the Martian carbon cycle well enough yet to have any real confidence. As with all tantalizing results about microbial extraterrestria

> but we don’t understand the Martian carbon cycle well enough yet to have any real confidence. As with all tantalizing results about microbial extraterrestrial life so far, this will probably turn out to be due to a physicochemical process we don’t yet understand. Or maybe not. That's right. I think NASA has learned its lessons from the original Viking missions that initially offered tantalizing evidence of biological chemistry only to turn out that there are non-biological explanations for the data. The lesson there is you have to understand the inorganic chemistry of Martian geology before going further in the search for biosignatures.