Apollo 16

Apollo 16 was the tenth crewed mission in the United States Apollo space program, the fifth and penultimate mission to land on the Moon, and the second to land in the lunar highlands. Launched on April 16, 1972, the mission was a critical endeavor in lunar geology, aimed at exploring the Descartes Highlands to determine the origin of the Moon's mountainous regions. Over the course of an 11-day mission, the crew conducted extensive scientific experiments, deployed advanced equipment, and returned with a substantial collection of lunar samples that fundamentally altered scientific understanding of the Moon's geological history.

Mission Overview

Apollo 16 launched from Kennedy Space Center in Florida aboard a Saturn V rocket. The mission spent 71 hours on the lunar surface, during which the crew conducted three extravehicular activities (EVAs), totaling over 20 hours of moonwalks. The mission concluded with a successful splashdown in the Pacific Ocean on April 27, 1972. It was the second of the Apollo "J-class" missions, which featured extended stays on the Moon, a greater focus on science, and the use of the Lunar Roving Vehicle (LRV).

Crew

The Apollo 16 crew consisted of three veteran astronauts:

• John W. Young (Commander): A highly experienced astronaut who had previously flown on Gemini 3, Gemini 10, and Apollo 10. Young became the ninth person to walk on the Moon.
• Charles M. Duke Jr. (Lunar Module Pilot): Making his first spaceflight, Duke was the tenth person to walk on the Moon and served as the primary geologist on the lunar surface.
• Thomas K. Mattingly II (Command Module Pilot): Originally slated for Apollo 13, Mattingly orbited the Moon alone in the Command Module, conducting crucial scientific observations and operating the Scientific Instrument Module (SIM) bay.

Mission Objectives

The primary scientific objective of Apollo 16 was to explore the Descartes Highlands, a region previously hypothesized by some geologists to be of volcanic origin. Scientists hoped that sampling this area would provide insights into the early thermal history of the Moon. Secondary objectives included deploying the Apollo Lunar Surface Experiments Package (ALSEP), testing the maneuverability of the Lunar Roving Vehicle in rugged terrain, and conducting ultraviolet astronomy observations using the Far Ultraviolet Camera/Spectrograph.

Spacecraft and Equipment

The Apollo 16 spacecraft comprised the Command and Service Module (CSM), named Casper, and the Lunar Module (LM), named Orion.

• Lunar Roving Vehicle (LRV): Apollo 16 carried the third LRV to the Moon, allowing Young and Duke to travel up to 4.5 kilometers from the landing site and transport heavy geological samples.
• ALSEP: The crew deployed a suite of instruments, including a passive seismometer, an active seismic experiment, a lunar heat flow experiment, and a lunar surface magnetometer, to transmit long-term data back to Earth.
• Scientific Instrument Module (SIM): Housed in the Service Module, the SIM bay contained a panoramic camera, a mapping camera, a laser altimeter, and a mass spectrometer, which Mattingly operated from lunar orbit.

Mission Profile

Launch and Transit

Apollo 16 lifted off on April 16, 1972. The journey to the Moon was largely uneventful, though the crew experienced minor issues with the CSM's environmental control system and a brief delay in the transposition, docking, and extraction maneuver.

Lunar Orbit and Landing

After entering lunar orbit, a malfunction in the CSM's main engine gimbal system threatened to abort the landing. Following extensive analysis by Mission Control, the landing was given the go-ahead. On April 21, Young and Duke descended in Orion, landing in the Descartes region, approximately 270 meters northwest of the targeted point.

Surface Operations

During their 71-hour stay, Young and Duke conducted three EVAs:

1. EVA 1: Deployment of the ALSEP and initial geological sampling near the landing site.
2. EVA 2: Exploration of the Cinco Craters and Stone Mountain using the LRV, where they collected significant rock samples.
3. EVA 3: A traverse to the North Ray Crater, the largest crater visited by any Apollo mission, where they sampled massive boulders ejected from deep within the lunar crust.

Return to Earth

After completing their surface operations, Young and Duke lifted off in the ascent stage of Orion and successfully rendezvoused with Mattingly in Casper. During the return journey, Mattingly performed a deep-space EVA to retrieve film cassettes from the SIM bay. The spacecraft splashed down safely in the Pacific Ocean on April 27, 1972, and the crew was recovered by the USS Ticonderoga.

Scientific Discoveries and Legacy

Apollo 16 returned 95.8 kilograms (211 pounds) of lunar samples, including the largest single rock returned by any Apollo mission, dubbed "Big Muley" (weighing 11.7 kilograms). The most significant scientific outcome of the mission was the refutation of the pre-mission hypothesis regarding the Descartes Highlands. Analysis of the samples revealed that the highlands were not formed by volcanic activity, but were instead composed of impact breccias—rocks shattered and fused by meteorite impacts. This discovery proved that the lunar highlands were shaped primarily by the heavy bombardment of the early solar system.

The mission also provided the first astronomical observations from the lunar surface using the Far Ultraviolet Camera, capturing images of the Earth's geocorona and various celestial objects. Apollo 16's successful exploration of the rugged highlands demonstrated the reliability of the Apollo hardware and paved the way for the final lunar mission, Apollo 17.