About four years ago, I wrote a piece for PJM on the possibility that evidence was building up for life on Mars.
The evidence I mentioned in that article is the way that there is an unexplained amount of methane, CH4, in Mars’ atmosphere. More suspiciously, it seems to vary with the seasons, which makes it seem more likely to be biological in origin. At the same time, I noted that the original Viking landers had had two experiments that appeared to indicate life, and one that was equivocal — leading to the conclusion that there was no life.
This week, a new paper has been published, doing a mathematical analysis of the original Viking data. That link will lead you to the abstract, which summarized says that they performed a more sophisticated mathematical analysis on the data, and have determined that the experiment “acted like” a biological source, and not like a non-biological phenomenon.