The guest speaker at the September society meeting was Mr Peter Rea from Cleethorps and district astronomical society. His visually stunning presentation was the Apollo 15 mission to the Moon in July and August 1971. He explained that this was the first of the three “J” missions designed to conduct exploration of the Moon over longer periods, over greater ranges, and with more instruments for scientific data acquisition than on previous Apollo missions. Major modifications and augmentations to the basic Apollo hardware were made.
The most significant change was the installation of a scientific instrument module in one of the service module bays for scientific investigations from lunar orbit. Other hardware changes consisted of lunar module modifications to accommodate a greater payload and a longer stay on the lunar surface, and the provision of a lunar roving vehicle.
The landing site chosen for the mission was an area near the foot of the Montes Apenniuns and adjacent to Hadley Rille. The site is on a dark mare plain near the sinuous Hadley Rille and the frontal scarp of the Apennine Mountains. This scarp is the main boundary of the Imbrium impact Basin, which is centered approximately 650 kilometers to the northwest.
Because of the variety of surface features, the Hadley-Apennine landing site permitted extensive geological exploration. During the approximately 67 hours on the Moon, the crew conducted a 33-minute stand-up extravehicular activity (EVA) in the upper hatch of the lunar module as well as three EVAs totalling about 18.5 hours on the lunar surface.
The photographic objectives of the Apollo 15 mission were designed to support a wide variety of scientific and operational experiments, to provide high-resolution panoramic photographs and precisely oriented metric photographs of the lunar surface.
There were two main geology objectives for this site. To collect rocks from the Apennine mountains and to study Hadley Rille, a volcanic channel near the landing site.
The target of the second EVA, was the edge of Mount Hadley Delta, where the pair sampled boulders and craters along the Apennine Front. During this moonwalk, the astronauts recovered what came to be one of the more famous lunar samples collected on the Moon, known as the “Genesis Rock.” Once back at the landing site, Scott continued to try to drill holes for an experiment at the ALSEP site, with which he had struggled the day before.
The Apollo 15 crew collected 370 individual rock and soil samples, including a deep drill core with material from 2.4 meters below the lunar surface, with a total mass of 77 kilograms.
Lunar anorthosites constitute the light-coloured areas of the Moon’s surface and have been the subject of much research. This sample provided by Mr Rea is from a outcrop on Earth in the US state of California.
Chemical analysis of the Genesis Rock indicated it is an anorthosite, composed mostly of a type of plagioclase feldspar known as anorthite. The rock was formed in the early stages of the Solar System, at least 4 billion years ago.