20 January 2017
Hipparchus is a fabulous crater to visit. Not only is it an exceptional formation to explore but it also offers a tremendous observing experience when you compare what one sees in the eyepiece with the views recorded by Robert Hooke, Tintin, Apollo 16 and the Lunar Reconnaissance Orbiter.
Robert Hooke (1635-1703) was an artist, biologist, physicist, engineer, architect, inventor and much else; a man who rubbed shoulders with many of the great minds of his time, and quarreled with most of them. In 1664 he published his masterpiece Micrographia: or Some Physiological Descriptions of Minute Bodies made by Magnifying Glasses, an exquisitely illustrated introduction to the microscopic world that lay all around.
Although this seminal work on microscopy is more noted for its impressive engravings of magnified insects than for its contributions to lunar topography, it does, however, contain the very first attempt to delineate a particular lunar feature… the crater Hipparchus.
Hooke made his astronomical observations with two, or perhaps three, telescopes: one of 12 feet focal length, with no aperture specified, although it was probably around two inches; and then he states that he was observing the Moon with a 30-foot refractor in October 1664. But clearly, the finest telescope to which he had access was a splendid instrument of 36 feet focus, with an object glass diameter of 3.5 inches. And while Hooke does not specify its magnification, it has been calculated from what he reported that he was working at a power of around ×173. In October 1664, Hooke used a 30-foot (perhaps a misprint for his favourite 36-foot) telescope to make his classic, detailed drawing of the single crater Hipparchus.
The first man to walk on the Moon was the Belgian astronaut and reporter Tintin who landed in Hipparchus in 1954. His lunar adventure was depicted in Explorers on the Moon – the seventeenth volume of The Adventures of Tintin, the comics series by Belgian cartoonist Hergé. It is the second of a two-part adventure begun in Destination Moon (1953) which gives a detailed account on the preparation and the launching of the expedition to the Moon.
Tintin’s first words on the Moon were, “For the first time certainly in the history of mankind, there is an explorer on the Moon!” I wonder how many people, reading his words in 1954 would have guessed the words of Neil Armstrong a mere 15 years later: “That’s one small step for (a) man, one giant leap for mankind.”?
Hergé certainly captured the heightened feelings of all those taking part in mankind’s first mission to the Moon: the nervousness of the astronauts before launch, the conditions under which they land, the radio transmissions between the astronauts and their team on the ground, the intense emotions at the moment of stepping onto the surface of the Moon and the joy felt at that moment by those back on Earth.
The Apollo 16 mission (April16–27, 1972) returned more photographs than any previous lunar mission. The dominant photographic mission was to record lunar surface features, with additional coverage of spacecraft maneuvers and views of deep space and earth. And among its photographs was this oblique view of Hipparchus.
The Lunar Reconnaissance Orbiter (LRO) is a NASA robotic spacecraft (launched on June 18, 2009) whose primary goal was to make a 3D map of the Moon’s surface from lunar polar orbit as part of a high-resolution mapping program to identify landing sites and potential resources, to investigate the radiation environment, and to prove new technologies in anticipation of future automated and human missions to the surface of the Moon. LRO continues to orbit the Moon. Its mission photos are absolutely amazing, showing us the entire Moon in unprecedented detail.
This ancient crater formed when the Moon was still relatively young (pre-Nectarian 4.6 to 3.92 billion years ago). Deformed and wrecked, it is barely visible owing to considerable modification due to both subsequent impacts and also to radial grooves and ridges from the Imbrium impact known as “Imbrium sculpture”. The western rim of Hipparchus has been all but worn away from impact erosion, and only low hills and rises remain to outline the feature. The wall to the east is somewhat more intact, but it too is heavily worn, and two deep clefts cut through it and parallel a sets of scars running through the south-central highlands.
The crater has a very large flat floor but no central peak which one would expect for a crater of this size – only a few mounds are dotted around. Hipparchus N and the ghost crater Hipparchus X lie on the floor which has been partially resurfaced by basaltic lava flow. There are two gaps in the northwest rim forming valleys that connect with the maria to the northwest. A rille named Rima Réaumur runs from this site to the outer wall of Réaumur
Horrocks lies entirely within the northeast rim of the crater. Halley is attached to the south rim, and Hind lies to the southeast. To the north-northeast is the bowl-shaped Pickering, and the flooded Saunder is located off the northeast rim.
What a glorious crater!
Copyright © Susan Young 2017