Apollo 17: The End of Humanity’s First Era of Lunar Exploration
Mission Overview
It was approaching midnight on December 7th, 1972, at Kennedy Space Center as the final countdown of the launch sequence began. At T-45 seconds, Commander Gene Cernan made the last alignment to the guidance computer, the final action required by the crew before launch. Moments later, at T-8 seconds, a blinding orange light erupted as Saturn V’s engines ignited, lifting the crew of Apollo 17 into the sky, following in the footsteps of the few before them. In the first seconds of liftoff on that cold December night, one could imagine the collective breath held by the crew and control team, not only because of the dramatic controlled explosion unfolding before them, but because of theprofound significance of this particular mission, highlighted perhaps most dramatically by the launch taking place at night, the first and only performed by the Saturn V. That significance was that Apollo 17 is the last mission of the Apollo Program that brought mankind to the Moon and further marks the last time to this day that man steps foot on the lunar surface.
The Apollo 17 mission was the 17th voyage in the Apollo Program, initially tasked with landing the first men on the Moon. The missions after that first landing all followed in spirit, but the specifics of those missions varied, each with a carefully selected landing zone and a suite of scientific instruments. In the case of Apollo 17, their focus was on geological surveying and sampling of materials found on the surface. So much so that after learning 17 would be the last Apollo mission, NASA scrambled to reschedule geologist Harrison Schmitt, who was initially planning to participate in the Apollo 18 mission. Having a trained scientist on board not only allowed for a more significant survey but also gave 17 “the distinction of being the only Apollo mission to carry a trained geologist to walk on the lunar surface”. The remaining crew members included Commander Eugene A. Cernan and Command Module Pilot Ronald E. Evans.
Three distinct landings were initially considered in the final planning phase: Alphonsus, Gassendi, and Taurus–Littrow craters. Eventually, NASA settled on Taurus–Littrow because Apollo 15 astronaut Al Worden believed he saw volcanic cinder cones in the center of the valley. Orbital photography provided by the Apollo 15 mission also confirmed that Taurus–Littrow would be a safe landing site.
Between 1960 and 1973, $25.8 billion was spent by the United States on the Apollo Program. This would equate to approximately $257 billion today. Unfortunately, it seems that the Apollo Program was largely funded together and not each mission individually, so the cost of 17 itself could not be found.
Mission Objectives
The crew began working on the main mission objectives of surveying and sampling after landing on the lunar surface. At 7:54 pm. Dec. 11th, at 20 degrees lunar latitude, 10 minutes north, and longitude 30 degrees 46 minutes east, the crew landed on the Moon. This was approximately 84 nautical miles northwest of the planned target but wasn’t too far to be serviceable. The mission objective was performed using primarily three methods: a heat flow experiment repeated from previous missions, a mass spectrometer, and a Seismic Profiling Experiment, as well as sample gathering. When Cernan and Schmitt started their second EVA, they began by repairing the right fender of the rover using laminated maps and small clamps because the fender was damaged when it was snagged by a rock on their first EVA. Over the course of the mission, Cernan and Schmitt were able to collect 110 kilograms of samples as they drove the lunar rover for a total distance of 35.7 kilometers. This was the greatest distance and number of samples gathered on any mission.
One of the most interesting moments of Cernan and Schmitt’s EVAs is when they discovered orange soil. Initially, Schmitt excitedly speculated that the coloration of the soil could be due to the volcanic activity believed to be seen on previous missions, but upon further examination using his expertise in geology, he came to the realization that this soil was far more likely to be excavated during an impact, and the soil was not likely to be volcanic. Rather, the dark material was excavated from a meteor impact. These discoveries underscored the scientific value of Apollo 17 and set the stage for the mission’s more technical experiments.
Mission Design
The three experiments used all served different yet equally important functions of analysis. The heat flow experiment was used to determine the rate of heat loss from the lunar interior. The mass spectrometer was used to sample and analyze the composition of the Moon’s atmosphere. And lastly, the Seismic Profiling Experiment was used to record vibrations of the lunar surface.
The heat flow experiment was deployed by connecting two probes to eight meters of cable joined at an electronics box. Both probes are lowered into boreholes where the attached thermometers read the temperature within. The instrument indicated a maximum temperature of 328 K at lunar noon and a consistent 290 K at lunar night. The mass spectrometer “intercepts and measures the downward flux of gases at the lunar surface”. This allows the study of the composition and variation of the lunar surface.
The Seismic Profiling Experiment was conducted by planting explosive packages at three sites and detonating them by command. The crew then measured vibrations within the surface to determine internal characteristics of the lunar crust at a depth of multiple kilometers.
Following these experiments, at 10:54 p.m. Dec. 14th, after the most samples were collected and the largest distance was traveled on any Moon mission, the Apollo 17 astronauts left the Moon’s surface for the last time, marking the end of the Apollo era. Apollo 17 remains one of the most scientifically productive lunar missions, and its achievements continue to impact our understanding of the Moon more than fifty years later.
