The Moon’s Mare Humorum, or Sea of Moisture, as observed by French astronomer, amateur entomologist, and artist Étienne Léopold Trouvelot in 1875. Though he spent his latter years producing thousands of astronomical illustrations, M. Trouvelot is more (in)famous for his role in accidentally introducing the European gypsy moth to North America. In the late 1860s he imported gypsy moth eggs to his home in Medford, Massachusetts, intending to cross-breed silk-producing moths with the disease resistant pests. Some of the insects escaped from his backyard and began to spread and multiply. By now, the pests cause an estimated $868 million per year in damage to trees of North America.

M. Trouvelot’s misfortune in his entomological endeavours led him to pursue a new career in astronomical illustration, after he observed several aurorae in 1870. He joined the staff at the Harvard College Observatory in 1872, and was invited to use the 26 inch refractor at the U.S. Naval Observatory for a year in 1875. A portfolio of his pastel astronomical observations was published in 1881 (image credit: The Trouvelot astronomical drawings: Atlas/NYPL Digital Gallery).