A few decades ago, a team of scientists reported in Nature that life on land is possibly over a billion years older than previously demonstrated. Their evidence came in the form of a chunk of ancient soil, or paleosol, that contained what they believed were once “mats” of microbial life, maybe including photosynthetic cyanobacteria (sometimes called blue-green algae). These microbial mats, researchers have noted, could be interpreted as an early record of a biological crust, or “biocrust.” Though there’s no consensus on exactly when biocrusts first appeared, over time these…
