50 years ago, NASA’s Apollo 15 mission paved the way towards our understanding of the Moon’s history with some amazing discoveries.
On 26 July 1971 David Scott, Alfred Worden and James Irwin launched atop a Saturn V rocket for the fourth mission to the Moon, Apollo 15. Alongside their usual experiments, they carried the Lunar Roving Vehicle (more commonly referred to as a ‘Moon Buggy’) which allowed them to travel further than any Apollo mission before. The Moon rock they brought back has helped us to develop the origin story of the Moon and paved the way for its future exploration.
The Apollo 15 mission was unique in many ways. The main difference to previous missions being that, where before Apollo astronauts spent a maximum of just over nine hours exploring the Moon’s surface in at most two extravehicular activities (EVAs), or moonwalks as they’re more commonly known, the astronauts of Apollo 15 performed three moonwalks totalling 18 hours and 37 minutes and travelled an impressive 17 miles around the landing site. Throughout the three moonwalks, the astronauts performed numerous experiments ranging from investigating the Moon’s magnetic field to monitoring the solar wind. Scott even performed a live television demonstration of Galileo’s free fall experiment by dropping a hammer and a feather at the same time to show that they fell at the same rate when in a vacuum.
Apollo 15 Hammer-Feather Drop
Commander Scott held out a geologic hammer and a feather and dropped them at the same time. Because they were essentially in a vacuum, there was no air resistance and the feather fell at the same rate as the hammer, as Galileo had concluded hundreds of years before.
Discoveries in Moon Rock
What really set the Apollo 15 mission apart from its predecessors was the intense geological training the astronauts received prior to the mission. Although missions 11, 12 and 14 all receive geological training before lift-off to allow them to learn how to take lunar samples, Apollo 15 was the first mission to focus on geological fieldwork and determining which lunar samples would be the most beneficial to bring home.
The first moonwalk of the mission was along the Elbow crater where astronauts Scott and Irwin collected samples from around the crater to see what lunar material would have been ejected when the crater was formed. It was during the second EVA that the most important discovery was made, when Commander Scott spotted a white rock on the Moon’s surface that reflected the Sun’s light. It was identified as plagioclase feldspar, more commonly known as anorthosite, and was one of the components of the Moon’s early crust. Geologists in Mission Control dubbed the sample the “Genesis rock” as it dates back over 4 billion years to the origin of the Moon and the Earth. During the same moonwalk the astronauts discovered olivine, a mineral formed in the Moon’s magma, suggesting that the Moon might not have been as cold and desolate and we see today.
Paving the Way for Future Exploration
The Apollo 15 mission showcased just what lunar secrets geological training can unlock and provided evidence for many theories about the Moon’s origin.
Ultimately, the success of the Apollo 15 mission, the Lunar Roving Vehicle, and the geological finds paved the way for the success of Apollo missions 16 and 17 which saw the astronauts travelling further across the Moon’s surface and making more extraordinary discoveries.
During Apollo 16 and 17, the astronauts made many more discoveries which changed our idea of what the Moon is made of. One of the most important was when Harrison Schmitt retrieved a sample of orange soil from Shorty Crater. Orange soil is made up of globules of black and orange glass which form on Earth during volcanic events, providing evidence of the Moon’s volcanic past.
You can see one of the Moon rocks brought back by the Apollo 17 mission in the National Space Centre’s Rocket Tower, some of the last to be brought back from the Moon by human hands!
A Mission of Firsts
Although not the first mission to the Moon, Apollo 15 was a mission full of firsts. The first to drive a vehicle on the Moon, the first to perform an EVA outside of Earth’s orbit, and the first to put a focus on geological training. These firsts helped to advance our knowledge of the Moon and provide vital lessons for future missions. On the 50th anniversary we should remember these discoveries and the revelations they have given us about our own special satellite.
About the author: Eleanor Morton graduated from the University of Leicester with a Masters in Physics. She is an aspiring science writer and can be found on Twitter @ElMortonSci.