Medicine’s Lunar Legacies Zaheer Toodayan* Fifty years have now passed since Man first walked on the Moon and nothing quite so pioneer- ing as the Apollo 11 mission has been accomplished since. The anniversary provides a suitable setting in which to reflect upon Earth’s only natural satellite, and for those whose lives predom- inantly revolve around healthcare, a useful opportunity to review the historical associations between medicine and the Moon. After providing some brief background information about the Moon’s craters and the nomenclature that applies to them, this monograph considers those physicians who made important contributions to selenology and presents a comprehensive tab- ulation of all eponymous lunar craters that are associated with the medical profession. In vain to do individuals hope for immortality, Origins of the Moon and Craters or any patent from oblivion, in preservations below the Moon. It is thought that the Moon – Luna in Latin – was creat- – Sir Thomas Browne (1605-1682), ed in the aftermath of a violent cosmic collision.2 The Hydriotaphia, Urne-Buriall, 1658.1 giant-impact hypothesis postulates that around 4.5 bil- lion years ago, a Mars-sized protoplanet named Theia3 ur Moon, the brightest celestial object in the collided with the young Earth and the material that night sky, has captured the imaginations of was ejected into orbit subsequently accreted to create Oonlookers in all ages. Its tranquility and re- the new Moon.4, 5, 6 moteness have enticed the adventurous spirit of Man, whose wanderlust culminated in a sensational series of There are a variety of craters that punctuate the lunar lunar landings fifty years ago. But even before Man surface with features corresponding to their age and lay foot upon it, the Moon was a metaphor for the mechanism of formation (Figure 1). Studies of lunar heroic and idyllic, and when the science of selenog- rocks and minerals suggest that many larger craters raphy first began this same sentiment found its way and impact basins8 were formed during a period of into systems of lunar nomenclature. A conspicuous intense instability in the solar system, around 3.9 bil- manifestation of this reverential tradition is the epon- lion years ago, which resulted in numerous massive ymous identification of the Moon’s craters. Bearing asteroid collisions with the rocky planets and their the names of distinguished doctors and medical scien- satellites.9 Populations of younger craters originated tists, many craters collectively chronicle the important more recently, in the last one billion years or so, and milestones and scientific breakthroughs that revolu- such craters are characterised by bright unweathered tionized modern medicine. ray systems of ejecta.10 Before we consider its medical associations, let us first All lunar craters were created through hypervelocity11 review how the Moon and its craters were formed, the impacts with meteorites, asteroids and derivatives of principles that govern visibility of the Moon’s surface, comets. Impacts between solid objects at these tre- and the historical development of lunar nomenclature. mendous speeds results in a series of high-energy events that excavate the target surface to form an im- pact crater. The craters are forged by a variety of forc- es during and shortly after impact, including melting, * Dr Zaheer Toodayan is a Basic Physician Trainee from Brisbane, vaporisation and the ejection and displacement of ma- Australia. Correspondence: [email protected]. terial from both projectile and target. In larger craters, Full Moon at dawn. The proximity of the Moon to the horizon creates two interesting effects – the illusion of a larger diameter gravitational forces may induce rim collapse and uplift and a warmer hue. Photo taken by author on 18th June 2019 from of the central meltrock within the transient cavity, re- Calamvale, Brisbane. sulting in complex crater configurations.12 9 Z. Toodayan Figure 1: The crater rich plains of the central and southern highlands as seen through an eight-inch Newtonian telescope. Shadowing accentuates details of craters near the lunar terminator. The larger craters at the extreme left of the image are Hipparchus (150 km, seen partially) and Albategnius (129 km), both complex craters with central formations. Younger cra- ters can be seen overlying older ones, whilst craters near the Moon’s southern limb (extreme right in this photo) demonstrate significant foreshortening.7 Photograph taken by author on 10th August 2016. Visibility of the Lunar Surface The extent of the Moon’s near-side that appears illu- minated to observers on Earth changes with the lunar Not all of the lunar craters are visible from Earth. Over phase. Although the sun-facing half of the Moon is time, tidal forces have caused the Moon to adopt a syn- always lit by sunlight, the changing position of the chronous rotation about our planet; that is, it takes the Moon in its orbit around Earth produces different per- same time for the Moon to complete a rotation about its spectives of this illuminated hemisphere, creating the own axis as it does to complete one revolution around lunar phases. The Moon’s phase waxes and wanes be- Earth. This results in the Moon always presenting the tween an unilluminated new Moon and a completely same hemisphere towards Earth (the near-side) with illuminated full Moon over the course of a lunar month the opposite hemisphere remaining unseen.13 Even so, (Figure 2). The shadowing effects created by the lunar due to the phenomenon of optical libration, slightly terminator, the demarcation band between lunar day more than fifty percent of the lunar surface is visible and night, allows for better appreciation of the Moon’s to observers during a lunar cycle. Libration exposes finer surface details. The first visions of the far-side an additional nine percent or so of the Moon’s surface of the Moon, the side that is always facing away from beyond the rim of the main disc and occurs due to the Earth, were provided by the Soviet Luna 3 space probe inherent geometry and dynamics of the Earth-Moon on 7th October 1959.17 system – the mild eccentricity of the Moon’s orbit (li- bration in longitude), the inclination of its orbital plane and axis of rotation (libration in latitude), the parallax A Brief History of Lunar Nomenclature created by the displacement of the Earth’s surface (and the Earth-bound observer) over the course of a single Man has probably had names for the Moon and its night (diurnal libration), and the small variation in the most visible features ever since language first originat- Moon’s speed of rotation about its polar axis as a result ed, but describing the Moon became a truly scientific of the tidal bulge of its nearside (physical libration).14 exercise with the invention of the telescope. Shortly 10 Osleriana Medicine’s Lunar Legacies Figure 2: Phases of the Moon as seen from the southern hemisphere. The central lower image shows a thin waxing crescent, occurring shortly after a new Moon.15 The Moon’s face becomes increasingly illuminated thereafter, as demonstrated in the left to right progression of images: a broader waxing crescent, first quarter (semi-illuminated), waxing gibbous and full Moon – this semi-cycle occuring over approximately one fortnight. Following a full Moon, which occurs when its orbit places it farthest away from the Sun, the phases wane in a reverse order until a new Moon is made once again, completing the lunar cycle. An entire cycle of lunar phases (a lunation) defines the synodic (lunar) month, which is a period of about 29.5 days.16 Individual photographs taken by the author between August 2016 and April 2018. thereafter, in 1610, the Italian polymath Galileo Galilei The first true lunar cartograph20 is attributed to the (1564-1602) published some of the first telescope-as- Spanish astronomer Michael Florent van Langren sisted sketches of the lunar surface in his astronomical (1598-1675) – Royal Mathematician and Cosmogra- treatise Siderius Nuncius.18 In analysing the details pher to King Philip IV – whose 1645 engraved map of highlighted by the Moon’s terminator, Galileo noted the Moon entitled Plenilunii Lumina Austriaca Philip- the topographical diversity of the lunar landscape and pica (Figure 3) identified its various surface features asserted the existence of mountains and valleys there- for the first time.21, 22 In accordance with the Plutar- on. He was the first to see, write about, and illustrate chian view that perpetuated the notion of the Moon the Moon’s many craters; structures he called “small as a second Earth,23 Langrenus’ map distinguished the spots” in order to distinguish them from the “great or dark lunar seas (Maria, singular Mare) from the bright- ancient spots” (the Maria) readily visible from Earth.19 er surrounding lands (Terrae, singular Terra). Com- plying with royal instruction24 he also systematically Following Galileo, the improving optics of astronom- designated craters with the names of ‘illustrious men’21 ical telescopes in seventeenth century Europe enabled and ‘foreigners of excellence in the sciences’25 – his increasingly accurate observations of the lunar surface. ‘Land of Dignity’ (‘Terra Dignitatus’) was populated Alongside these advances, the astronomers of the age with identities of Catholic significance26 and the names recorded progressively detailed maps of the Moon to of a selection of influential stargazers were clustered describe, communicate, and distribute their findings. in the ‘Sea of Astronomy’ (‘Mare Astronomicum’).27 Of the many efforts undertaken in this emerging sci- ence of selenography, the contributions of some key Langrenus’ nomenclature was not adopted by Johannes astronomers played a pivotal role in establishing the Hevelius (1611-1687), the eminent Polish astrono- convention by which the Moon’s topographical fea- mer who discovered the longitudinal libration of the tures were classified and named.