The Moon has captivated human imagination for millennia, but it’s only in recent decades that we’ve begun to unravel its mysteries through scientific exploration. NASA‘s Science Mission Directorate (SMD) is at the forefront of this endeavor, with the Exploration Science and Strategy Office (ESSIO) leading efforts to achieve Moon to Mars (M2M) science objectives. These objectives are derived from various scientific disciplines, including Astrophysics, Planetary Science, Heliophysics, Earth Science, and Biological and Physical Sciences.
NASA’s lunar science priorities are closely aligned with the top three lunar priorities outlined in the 2023-2032 Origins, Worlds, and Life (OWL) Planetary Decadal Survey. To address these priorities, NASA has recommended two key missions: Endurance-A and the Lunar Geophysical Network (LGN). These missions, along with Commercial Lunar Payload Services (CLPS) and Artemis human missions, will significantly advance our understanding of the Moon and pave the way for future exploration.
This article explores the high-priority lunar science objectives that NASA plans to tackle through these missions, offering insights into the Moon’s history, its relationship with Earth, and its role in the broader context of our solar system.
Understanding the Moon-Earth Connection
The Moon’s History and Life on Earth
One of the fascinating aspects of lunar science is its potential to shed light on the history of life on Earth. By studying the Moon, scientists hope to uncover connections between lunar geological or compositional changes and major evolutionary events on our planet. Current research suggests that Earth received most of its essential elements for life, including carbon and nitrogen, from the planetary collision that created the Moon over 4.4 billion years ago.
The Endurance mission plans to collect samples from the South Pole Aitken (SPA) Basin, a largely unexplored region of the Moon. These samples could provide invaluable insights that may reshape our understanding of the origins of life on Earth.
Earth and Moon Formation
The formation of Earth and the Moon is a topic of ongoing scientific investigation. Analysis of samples from NASA’s Apollo missions has revealed that the Earth and Moon share remarkably similar isotopic compositions. This has led scientists to hypothesize that both bodies resulted from a massive collision between a proto-Earth and a Mars-sized planetary body, often referred to as Theia.
However, our current understanding of the Moon’s bulk composition and interior structure is limited by the lack of active seismometers on the lunar surface. The lunar interior holds key information about the formation of Earth, the Moon, and the entire solar system. For instance, if the Moon’s core is found to be significantly larger than currently believed, it could dramatically alter our understanding of planetary formation processes.
The LGN mission plans to address this knowledge gap by placing at least four seismometer nodes in various regions around the Moon. This expanded network will provide a clearer picture of the Moon’s interior makeup, complementing the data obtained from seismometers deployed during the Apollo missions.
Exploring the Moon’s Geological History
Age Differences in Lunar Rocks
The Moon, being over 4.5 billion years old, has undergone significant changes throughout its existence. Based on samples returned by the Apollo missions, scientists have inferred that the Moon was initially mostly molten and gradually cooled and solidified over time. However, the Endurance mission aims to provide a new dataset by returning surface samples from the SPA Basin, a previously unexplored region of the Moon.
The SPA Basin is one of the largest and oldest impact features in the solar system. Its thin crustal layer, resulting from numerous impacts over time, potentially provides access to the lunar mantle. This unique characteristic makes it possible for Endurance to obtain samples of some of the oldest geological materials in the solar system. The chemical composition of these samples, combined with in-situ data from Endurance’s scientific payloads, will offer scientists valuable insights into the formation of the Moon, Earth, and other planetary bodies.
Late Heavy Bombardment Era
The SPA Basin, as the earliest-formed surface area of the Moon, holds a wealth of information about lunar and planetary science. Of particular interest is its potential to provide new insights into the theorized Late Heavy Bombardment, an event thought to have occurred approximately 4 billion years ago.
The Late Heavy Bombardment era had a profound impact on the solar system, possibly even causing planets to swap orbits. By studying surface samples from the SPA Basin, scientists hope to gain a better understanding of this period’s significance and timing. This knowledge will help clarify the geological and geophysical history of all planetary bodies in the solar system.
Through isotopic dating of surface samples returned by Endurance, scientists plan to establish more accurate ages of key impact basins across the Moon. This data will contribute to a more precise chronology of lunar and solar system events.
Understanding Lunar Impactors
The Moon’s surface bears countless scars from impacts over billions of years. Studying these bombardment areas provides valuable information about our planetary history. Given the close proximity of the Moon and Earth, scientists can infer that if the Moon was bombarded by impactors containing specific materials, Earth likely received similar materials as well.
The Endurance mission plans to return surface samples from significant impact locations. Scientists will analyze these samples to gather information about the materials carried by the impactors. Key questions they hope to answer include: What types of objects were hitting the Moon, and when? How were materials distributed across the lunar surface? Was water one of the materials delivered by these impacts? Were the building blocks of life brought to both the Moon and Earth, with Earth’s conditions being more conducive to fostering that life?
The answers to these questions could potentially unlock new insights into the origins of life in our solar system.
Calibrating Solar System Chronology
Establishing Precise Lunar Impact Chronology
Accurate chronology is fundamental to scientific understanding. In the context of lunar science, establishing a precise chronological measurement for lunar impacts is essential, as it informs models of solar system origins and evolution.
The Endurance mission will enable scientists to measure the radiometric ages of surface samples from terrains older than 3.9 billion years and compare them with those from terrains younger than 3 billion years. This will allow for a more accurate resolution in measuring the chronology of planetary events.
Additionally, obtaining a larger sample size from a greater variety of locations will significantly enhance the dataset used to model lunar cratering history. Understanding the relationship between surface crater density and age will be a significant breakthrough in calibrating the lunar timeline. Any changes to the lunar impact timeline could shift our understanding of collision events throughout the solar system.
The Moon as a Solar System Timekeeper
Based on isotopic analysis of samples returned from the Apollo missions, scientists have hypothesized that between 4.1 and 3.8 billion years ago, the lunar surface was heavily bombarded by asteroids. This period, known as the Late Heavy Bombardment (LHB), has become a key reference point for understanding the absolute timing of events throughout the solar system. In essence, lunar chronology serves as the solar system’s timekeeper.
Understanding the timing of lunar impact events has far-reaching implications for our knowledge of the solar system’s history. The present-day lunar impact rate can provide researchers with clarity about lunar chronology. By using LGN seismometers in conjunction with lunar observations of impact flashes, fresh impact craters, and sample returns from Endurance, scientists will gain a more comprehensive understanding of the solar system’s timeline.
Investigating the Moon’s Interior
Processes Shaping the Moon’s Interior Structure
Many planetary bodies, including Earth, were formed through volcanic and magmatic processes. Tidal forces also play a significant role in shaping planetary crusts and interiors. However, questions remain about how external (exogenic) and internal (endogenic) events affected the Moon’s composition, and how these events relate to tidal influence. Understanding these relationships is key to illuminating the past, present, and future of the Moon, Earth, and the rest of the solar system.
Both the LGN and Endurance missions will contribute to answering these questions. LGN will monitor seismic activity, electromagnetic sounding data, and heat flow around magma plumes. This data will allow scientists to compare current heat production with past heat production, providing insight into how magmatic processes have changed over time. Analysis of Endurance surface samples will offer additional information about the volcanic processes that shaped the Moon.
Mapping the Moon’s Internal Structure
While we have a considerable understanding of Earth’s internal composition due to its accessibility, our knowledge of the Moon’s interior is more limited. NASA currently has some data about the Moon’s internal layering based on returns from the Apollo seismic network. However, the geographic placement of these seismometers limits the insights that can be gained from seismic data.
The LGN mission aims to provide geographically and temporally expanded seismometer data, which will offer a more accurate picture of the Moon’s bulk composition. This data will be crucial for establishing a clear and accurate understanding of the Moon’s interior, potentially furthering our understanding of the interiors of other planetary bodies as well.
Tidal Influence on Crustal Structures
The crust, or outermost layer of a planetary body, is key to understanding its overall structure and history. Tidal forces exert a significant influence on crustal formation and evolution. By studying the tidal influence on the Moon’s crust, scientists can gain context and clarity for all crustal measurements, as well as understand if and how tidal activity deforms the Moon’s structure.
Data from the LGN mission will provide a more complete picture of the Moon’s interior. This information will allow scientists to better understand tidal influence not just on the Moon, but throughout the solar system.
Tectonic Activity on Other Planetary Bodies
Earth is considered the most tectonically active planetary body in our solar system, with a unique set of geological and scientific processes. However, our understanding of tectonism on most other planetary bodies is largely theoretical, based on mineralogical and geological studies using remotely sensed data.
By gaining a seismic understanding of planetary bodies like the Moon and Mars, scientists will be able to refine their theories about the tectonism of planets elsewhere in the solar system. This knowledge could extend even to distant bodies like Pluto, despite its icy exterior.
The LGN mission aims to provide groundbreaking seismic data on the Moon, similar to what the InSight mission has done for Mars. This data will contribute to our understanding of tectonic activity across all planetary bodies in our solar system.
The Moon’s Magnetic History
Based on currently available data, scientists believe that the Moon does not produce a magnetic field today. However, evidence suggests that this wasn’t always the case.
The Moon is thought to have had a magnetic field generated by its liquid outer core until between two and four billion years ago. Understanding the history of this magnetic field could provide answers to questions about the formation of both the Moon and Earth. Over time, as the core cooled and solidified, the Moon lost its magnetic field.
There are geomagnetic anomalies in different locations around the Moon that intrigue scientists. These spots might help unlock the magnetic (and therefore volcanic and magmatic) history of the Moon, providing insights into how the Moon lost heat over time.
The LGN mission will deploy seismometers, magnetometers, and electromagnetic sounding devices to provide high-resolution measurements. These instruments will allow scientists to study the orientation of known rocks in the Moon’s interior, potentially revealing more about the direction of the Moon’s long-lost magnetic field.
Composition of the South Pole Aitken Basin
The Moon’s composition is very similar to that of Earth, but there are notable differences. Samples from the South Pole Aitken (SPA) Basin will provide a unique and expanded context for scientists in establishing the origins of lunar materials, and by extension, the origins of the Moon and Earth.
Samples collected by the Endurance mission will also help explain why the crust is significantly thinner on the lunar near side than on the far side. The SPA Basin’s relatively thin crust suggests that lower crust or upper mantle components were exposed or incorporated into impact melt, giving scientists easier access to these deeper materials.
Summary
NASA’s lunar science priorities encompass a wide range of objectives, from understanding the Moon’s formation and evolution to using lunar data to calibrate our understanding of solar system chronology. The Endurance-A and Lunar Geophysical Network (LGN) missions, along with other initiatives, are set to provide unprecedented insights into the Moon’s history, composition, and internal structure.
These missions will not only enhance our understanding of the Moon itself but also shed light on Earth’s history, the origins of life, and the broader context of planetary formation and evolution in our solar system. By studying the Moon’s impactor history, internal composition, magnetic field evolution, and tectonic activity, scientists hope to refine theories about planetary processes throughout the solar system.
