the huge collection of photographic plates assembled by Earl C. Slipher since 1907. As to the planet Jupiter, Fokas devised a novel factor for the expression of atmospheric activity. At the end of the same year, he resigned from his position at the Athens Observatory to work at the IAU planetary observations collection center at the Observatory of Paris-Meudon. In his new position, having at its disposal more than 14,000 photos, he continues publishing and pursuing his own observations from Pic du Midi and Meudon. In Meudon, the completion by John Fokas cartographic work of planet Mars, commenced by Eugene Antoniadis, with the additional use of photographic and photometric techniques, influenced IAU in adopting the nomenclature system of Antoniades for the planet, making the official names of all almost all major areas of being Greek. Focas died on 3 January 1969, at the age of 60 from a heart attack while in Greece, where he was visiting for the holidays. Named after him was the crater Fokas (Focas) in the southern hemisphere of the Moon, with a diameter of 22 km, as well as the crater Fokas (Focas) in the northern hemisphere of Mars with a diameter of 76.5 km. See also Phokas (Byzantine family) References 1909 births 1969 deaths 20th-century Greek astronomers 20th-century French astronomers Greek emigrants to France Scientists from Corfu