Life on the Rocks is a fascinating account of a scientific expedition to a craggy archipelago off Brazil, where conditions may unlock secrets about possible life forms on Europa, Enceladus, and other nearby celestial bodies.
It's a great overview of the logistics and risks of these expeditions, including the story of the ill-fated Sea Link expedition in 1973 that killed two of the four crew members. The reason these scientists take such risks is the tantalizing possibilities for life in chemosynthetic environments rather than photosynthetic environments at or just below earth's surfaces.
The rock here could also be harboring entirely new forms of life. Klein explains that a chemical reaction between seawater and the iron in mantle minerals creates hydrogen molecules. Microbes, single-celled or multi-celled microorganisms, feed off this hydrogen. These organisms are similar to those that existed on Earth billions of years ago and may be closely related to our planet's earliest life forms. Klein and his team will seek out microbes in the deep and analyze the chemical processes within the mantle rocks as they occur. In doing so, the scientists hope to catch a glimpse of early life systems—a sort of window back in time to our most primitive selves, and perhaps to our alien counterparts.
"Icy moons of Saturn and Jupiter, Europa and Enceladus, have water below their surfaces; we know that," says Klein. "And these moons contain the same rocks that are on these islands." If distant moons in our solar system have the same rock, and the same water, they could have the chemical processes that feed the same basic forms of life here on Earth.
Bonus video: more footage from the dive: