The Moon: The First Step To Understand Our Solar System

A current NASA’s mission is uncovering details about the Moon, but we might have to wait a little longer to have the full picture.

Photo by NASA on Unsplash

The Moon is essential to the Earth. So crucial, that our planet would be at risk if one day, all of a sudden, the Moon simply disappeared. Without the Moon, the Earth would suffer and, thus, life in it. How so?

The Moon is responsible for tides and Earth’s stabilization. Tides are crucial for life in the ocean, particularly for some types of fish and sea turtles. These animals would be literally lost in the absence of our lunar companion as they have evolved to be tuned to high and low tides. The Earth would also be disoriented in the Moon’s absence. As we know, the Earth not only orbits around the sun but also acts as a giant spinning top that wobbles. This wobble is the circular motion produced when the Earth tilts while rotating around its axis. Without the moon around to temper it, this wobble could speed up erratically (yet very slowly.)

…the poles would be burning hot and the equator freezing cold. In effect, removing the Moon would spell extreme climate change.

While the Moon can help us make sense of our life on Earth, it might also be the way to understand our presence in the universe.

Originated about 4.5 billion years ago, the Moon has witnessed the evolution of our solar system. This means that our lunar companion likely holds a historical record of the events that happened many years ago. The Moon’s core and mantle may hold information about early geological processes such as the formation of rocky planets. And the Moon’s surface, a rich archive of many, if not all, inner solar system events.

However, according to the National Academies, what is known about the Moon’s origin and morphology is still part of major hypotheses:

• The Moon originated from the debris formed after the impact of a large Mars-sized body with Earth.
• Following lunar formation, the outer surface of the Moon was molten. This lunar magma was the earliest crust of the Moon, and from it, lunar rocks were formed.
• Lunar craters formed due to the terminal cataclysm (aka Late Heavy Bombardment), where massive objects impacted the Moon.

While resolving these major hypotheses may help understand the Moon’s formation and that of our solar system billion years ago, today, the Moon is still a mystery and occupies the first step in the exploration road-map of our solar system.

NASA’s Lunar Reconnaissance Orbiter (LRO)

Artistic representation of the LRO spacecraft orbiting the Moon. Credits: NASA.

In line with the solar system exploration road-map, in 2009, the National Aeronautics and Space Administration (NASA) launched its first mission to the Moon as part of the Lunar Precursor Robotic Program (LPRP): the Lunar Reconnaissance Orbiter (LRO).

Although this mission was thought to last only a few years, today NASA’s LRO spacecraft is still orbiting the Moon.

Exceeding expectations, LRO has collected more data than three times the printed collection of the Library of Congress, one of the world’s largest libraries. LRO’s data is so large that only one of its instruments acquired more data than obtained from combined planetary missions to date.

But the LRO spacecraft has, in fact, not just one, but seven powerful instruments. These instruments were built in collaboration with teams from the U.S. and Russia and were specially designed to examine different characteristics of the Moon’s surface and environment.

Here a brief summary of each of them:

• The Cosmic Ray Telescope for the Effects of Radiation (​CRaTER) characterizes the lunar radiation environment, allowing scientists to find potential hazards to life.
• The Diviner Lunar Radiometer Experiment (DLRE) measures temperatures in the surface and subsurface, helping identify cold lunar areas that are thought to bear billion-years-old ice deposits.
• The Lyman-Alpha Mapping Project (LAMP) searches for surface ice and frost in the polar regions and provide images of permanently shadowed areas that are very cold and thus might hold water ice.
• The Lunar Exploration Neutron Detector (LEND) provides evidence of water ice near the moon’s surface by creating high-resolution maps of hydrogen distribution and gathering information about the neutron component of the lunar radiation environment.
• The Lunar Orbiter Laser Altimeter (LOLA) basically allows the generation of a full 3-D map of the Moon’s topography, which helps identify permanently illuminated and permanently shadowed areas. It is thought that the illuminated regions may be the right places for a future solar power station.
• The Lunar Reconnaissance Orbiter Camera (LROC) takes black-and-white, coloured, and ultraviolet photos of the entire surface down with 100 to 1-meter resolution, aiding in the determination of lighting conditions as well as safe landing sites for future human expeditions.
• The Miniature Radio Frequency (Mini-RF) is an advanced radar used to image polar regions and search for water ice. It has also been used to demonstrate that communication with an Earth-based ground station from the Moon is possible.

While data processing and collecting is still ongoing, recently NASA has shown the world some of their most surprising results:

2020 NASA’s LRO Mini-RF announcement

In the news released in early July, NASA’s LRO Mini-RF team announced the radar instrument’s first results. According to their studies, the lunar craters in the North Pole hold patches of ice. But that was not all…

Mosaics from 70° to the pole for both the north (top) and south (bottom) polar regions. The left-hand images show radar brightness whilst the right-hand colour images also show the circular polarization ratio. Credits: NASA.

The study also suggested that the lunar subsurface is more metallic than its surface. These researchers identified a correlation between the Mini-RF radar data and additional metal oxide maps (obtained from Japan’s Kaguya mission and NASA’s Lunar Prospector spacecraft). This correlation clearly suggested that a metal-rich layer exists below the Moon’s surface, composed of iron and titanium oxides.

Although these results were not expected, they point to increasing evidence that metallic content in the Moon is rather diverse and non-uniform. Lunar rocks obtained from Apollo 11 mission showed to be less metallic than the composition of the Earth’s core. However, an examination of lunar maria (or seas) returns an opposite result, with maria rocks bearing a richer metallic content than rocks from Earth.

…the new study can’t directly answer the outstanding questions about the Moon’s formation, but it does reduce the uncertainty in the distribution of iron and titanium oxides in the lunar subsurface and provide critical evidence needed to better understand the Moon’s formation and its connection to Earth.

To validate these results, the team in charge of the Mini-RF instrument expects to analyze the lunar craters in the South Pole to see if the same metallic trend is observed in this region.

While the lunar composition is still a mystery, with these new results, we can see a bit more clearly than before. But to find a definite answer, real (meaning physical) lunar samples will have to be brought back to Earth. And that will likely happen during the next visit to our nearest neighbour, which is planned for 2024. So, hang tight!