Eight of the 137 microorganism samples used to measure biosignatures for the catalog. In each panel, the top is a regular photograph of the sample and the bottom is a micrograph, a 400x zoomed-in version of the top image. Our aim was to achieve diversity in color and pigmentation.

Top left to bottom right: Bacillus sp. (Sonoran desert, AZ, USA); Arthrobacter sp. (Atacama desert, Chile); Chlorella protothecoides (sap of a wounded white poplar); Ectothiorhodospira sp. str. BSL-9 (Big Soda Lake, NV, USA); Anabaena sp. (with green fluorescent protein; stagnant freshwater); Phormidium sp. (Kamori Channel, Palau); Porphyridium purpureum (old woodwork at salt spring, Boone’s Lick State Park, MO, USA); Dermocarpa violacea (aquarium outflow, La Jolla, CA, USA).

Online link to the article: Surface biosignatures of exo-Earths: Remote detection of extraterrestrial life.