The Jesuits on the Moon

Did you know there are Jesuits on the moon? Well, sorta. A lot of folks don't know, but today there are at least 38 craters on the moon named after Jesuit priests, all of whom were renowned scientists and astronomers. Some craters were named more recently, but as many as 35 can be traced back more than 350 years. One of the earliest records we have of these craters is a 17th century selenograph, which shows the location many of the craters.

The late Joseph MacDonnell, S.J. of Fairfield University describes the selenograph and how 35 of the names came to be:

Since 1645 selenographers had named at least 40 craters to honor Jesuits, but 5 have been renamed since then. Some of the craters are on the far side of the moon. When looking at the moon these craters can be located by eye when noting their position relative to the large Copernicus (O) crater with the distinctive "crater steaks" radiating from it like the stem of an orange.


At the entrance to the Smithsonian's Moon exhibit is a large copy of one of the earliest (1651) selenographs. This map, taken from a Jesuit book Almagestum novum, was composed by the Jesuit astronomers Riccioli and Grimaldi and across the top is written: "Neither do men inhabit the moon nor do souls migrate there".

It is the best known of all selenographs and has been used by most scholars for lunar nomenclature for three centuries. During these centuries astronomers took turns naming and renaming craters which resulted in conflicting lunar maps. In 1922 the International Astronomical Union (IAU) was formed, and eventually eliminated these conflicts and codified all lunar objects: 35 of the 40 Jesuit names survived to be listed in the National Air and Space Museum (NASM) catalog which identifies about 1600 points on the moon's surface.

And why were their names used to identify the craters in the first place? MacDonnell continues:

It would be a mistake to think that the Jesuit names are on selenographs only because other Jesuits put them there. Rather it was a convergence of astronomers' opinions over three centuries: map makers before and after Riccioli confirmed the decisions again and again that these 40 men deserved this honor. This is not surprising. Recent histories emphasize the enormous influence Jesuits had not only on mathematics but on the other developing sciences such as astronomy. Historians of science always listed a surprisingly large number of Jesuits among the greatest scientists and mathematicians of all time. They were at the cutting edge of the sciences. For instance, by the time of the suppression in 1773, of the world's 130 astronomy observatories, 30 were operated by Jesuits. Furthermore Jesuit names are still being added to the list by the I. A. U.

And just who are these Jesuits? Well, among them is the great Christopher Clavius, who was the main architect of the Gregorian Calendar and inspired mathematicians like Leibniz. Also among them is Matteo Ricci, and also Francesco Grimaldi, who inspired Isaac Newton in the study of optics.

Of course, you can view detailed information and images of these craters on-line, courtesy of The-Moon Wiki.