Free Astronomy Magazine July-August 2019

ASTRONAUTICS 5 L et us continue and complete our contribution to the cele- brations of the fiftieth anniver- sary of the conquest of the Moon, the first part of which was pub- lished in the May-June issue. The goal remains to highlight the rea- sons why NASA chose specific sites for the six human landings and the importance that these sites had, and still have, from the point of view of our gained knowledge of the geological evolution of the Moon.After sampling ‘marine’ ter- ritories and the Fra Mauro Forma- tion, geologists were eager to direct the astronauts into a moun- tainous environment, but no such site had been sufficiently inspected to certify it for a landing. However, there was no shortage of reachable alternatives. In addition to the ap- parently volcanic structures of Mar- ius Hills and Davy Rille, there was a system of dark-looking ridges and gullies in Mare Serenitatis, which Apollo 14 planned to visit before being redirected to Fra Mauro. At first, Apollo 15 was supposed to be an ‘H’ mission (precision land- ing, with a stay of up-to two days on the Moon and including two ex- travehicular activities), but on Sep- tember 2, 1970, it was decided to turn it into the first ‘J’ mission, able to stay longer on the Moon and with greater mobility on the sur- face. For this reason, a site with mul- tiple structures was really needed to take advantage of the huge explo- ration potential offered by the Lunar Roving Vehicle (LRV). The fa- vorite target was a new candidate: Hadley Rille, east of Mare Imbrium. Of the two existing types of lunar rilles, linear and sinuous, Hadley is one of the most impressive among the sinuous rilles. It starts in an A POLLO 15 − Panoramic view of the Apollo 15 operational area. [NASA, Project Apollo Archive; image merging by Astro Publishing]