this article a few months back, thinking it would be fertile ground for fiction. In a nutshell: Mono Lake in California has built up over the millennia one of the highest natural concentrations of arsenic on Earth. Dr Wolfe-Simon believes that the microbes in the lake's mud may utilize this arsenic in it's own chemical make-up, rather than the chemically similar phosphorus that the rest of life on Earth uses. She is exploring, and a great quote is coming up, if these microbes' "biological make-up is so fundamentally different from that of any known life on Earth that it may provide proof of a shadow biosphere, a second genesis for life on this planet."
A shadow biosphere. Life springing up independently not once, but twice on Earth. Perhaps more than twice.
What brought this article to mind was one in yesterday's news, stating that water and organic compounds have been detected in asteroids, and likely supplied the early Earth, and every other large body in the solar system, with water and complex carbon molecules.
Life has been found in every conceivable niche on Earth, from underwater volcanic vents to Antarctic snowfields. Complex organic compounds have been found on asteroids, on comets, on the moons of Saturn.
We live in a prodigal universe. Endless summer.
Ripeness is all.