While abiotic explanations are the more plausible, biotic explanations may not be ruled out yet. The first is the source of localised methane apparently venting from a couple locations on Mars. Certain bacteria on Earth are known to make methane as a byproduct of their life cycle. There are geothermal abiotic ways to make methane too. Earth biology has a preference for one isotope of carbon where geothermal methods would not care so looking for an unbalanced isotope signal within the methane would be a biomarker and favor the biological interpretation if identified. The second, also on Mars, is the possibility of an extremophile in the Martian atmosphere that readily makes a meal of the methane that is escaping presumeably from the subsurface. A recent Nature article found that the destruction of the methane is happening much faster than it should, by a factor of around 600. Yet such violent destruction seems not to affect other molecular species. It seems particular to methane and possibly most organic compounds. Even the organic background supplied by comets and asteroids and meteors seems rather absent in measurements observed so far. How such microbes can be so voracious and yet themselves remain immune to the same harsh effects or canibalism would present a mystery as well. The third signal comes from Venus. The surface is thought to be too intemperate for life, but airbourne life in the upper clouds has been considered by some. Recently a white spot was reported in the upper atmosphere of Venus. In this remote respect, one could look at it like it was a bright white algal bloom akin to large patches of Red Tide sometimes seen in our oceans.