The unseen engineers
The famous sailing stones of Racetrack Playa slide across a surface that is not lifeless. The dry lakebed is coated in a dark, bumpy layer of biological soil crust, a complex community of microorganisms dominated by cyanobacteria. An important organism in this ecosystem is Microcoleus vaginatus, a filamentous bacterium that forms bundles sheathed in a sticky polysaccharide slime. This secretion, known as an extracellular polymeric substance (EPS), binds the fine clay particles of the playa together. The resulting cohesive mat stabilizes the ground, preventing the fierce desert winds from carrying the soil away as dust.
This microbial crust practices a survival strategy called anhydrobiosis, or life without water. The organisms can enter a dormant, desiccated state for years or even decades, enduring the extreme temperature swings and intense ultraviolet radiation of Death Valley. In this state, their metabolic activity becomes undetectable. They are, for all practical purposes, in suspended animation, waiting for the rare event that brings them back to life: rain. The playa receives only about 3 to 4 inches (76 to 102 millimeters) of precipitation annually, making these revivals infrequent.