Going to the dark side: Yale scientist helps NASA understand moon’s origins

Earth and planetary scientist Jun Korenaga will be part of the science team for CLOE, a NASA-funded project looking at the moon’s origin.
An image of the moon's south pole

The Center for Lunar Origin and Evolution will provide scientific advances to support human exploration of the Moon, particularly its oldest and largest impact basin, which extends from near the south pole to cover much of the far side's southern hemisphere. (Courtesy of NASA/Goddard)

Over the next five years, Yale geophysicist Jun Korenaga will be part of a scientific project funded by NASA to study the origin and early development of the Earth’s moon.

The ambitious project, known as the Center for Lunar Origin and Evolution (CLOE), will conduct basic research in support of future human and robotic exploration of the far side of the moon. On May 11, NASA announced funding for five lunar science and lunar sample analysis research projects — including $7.5 million for CLOE — as part of NASA’s Solar System Exploration Research Virtual Institute (SSERVI).

Korenaga, whose research focuses on how Earth evolved to support life, is part of a team that includes 18 scientists from seven U.S. institutions and international collaborators that will work with CLOE. Led by the Southwest Research Institute in Colorado, the project will coordinate its efforts with ongoing NASA lunar science missions such as Artemis, which is expected to send humans back to the Moon later in this decade, and the Commercial Lunar Payload Services Initiative, which will deliver needed technology and equipment to the moon.

In an interview with Yale News, Korenaga, a professor of Earth and planetary sciences in Yale’s Faculty of Arts and Sciences, describes his role in CLOE, what we still don’t know about the formation and early evolution of the moon — and why a new understanding of these mysteries is important.

What makes the moon advantageous as a site for further study?

Jun Korenaga: The moon preserves the record of ancient conditions and events, and it is also accessible for human exploration. The moon thus has a tremendous potential to provide fundamental advances in our understanding of the origin and early evolution of the solar system. It is thought that the moon formed via a gigantic collision with Earth at the end of Earth’s formation, and the clues needed to unravel the nature of this event are still on the moon.

What sort of clues would you be looking for?

Korenaga: It is now appreciated that the planets in our inner solar system — Mercury, Venus, Earth, and Mars — were strongly affected by the orbital migration of the giant planets, such as Jupiter and Saturn. But the timing and nature of this dramatic process remains uncertain. Critical data needed to resolve these issues is encoded in the moon’s record of ancient impact craters and basins. By accurately interpreting the lunar crater record, we not only obtain the fundamental calibration needed to estimate the ages of cratered terrains across the solar system, but we also gain insights into the environment of the early Earth — an environment that has been erased by our planet’s active geology.

What data can CLOE and Artemis provide that we did not get from previous moon missions?

Korenaga: The Apollo missions of the 1960s and 1970s collected extensive data, but they focused on the near side of the moon, which helps us understand the moon’s current composition and its history for 4 billion years.

Our new project will explore the approximately 2,500-kilometer-wide, south pole basin. It is the oldest and largest impact basin on the moon and will provide data on the moon’s first 500 million years, which is not particularly well understood.

What is your role in the project?

Korenaga: I’m involved in revealing the conditions surrounding the origin of the moon.

As I mentioned earlier, it is generally believed that the moon was formed by a gigantic collision between the proto-Earth and a huge impactor, as large as Mars or perhaps even larger. The nature of this collision has been highly debated. A simple collision cannot explain the geochemical signature of the moon as well as its orbital characteristics.

One way to investigate the origin of the moon is to reconstruct the Earth-moon system in its early days. My group at Yale has been working on various aspects of the early Earth, making my group well-suited to address this early evolution of this system. I recently published preliminary results on this issue. But there are a few important complications — such as lunar magma ocean and orbital dynamics — that still need to be incorporated into my theory.

Is tidal evolution a factor, as well?

Korenaga: Yes. When the moon was formed, it was located very close to Earth, a distance that is equivalent to three-to-five times Earth’s radius. But because of tidal interaction, the moon has receded to its current position at about 60 times the Earth’s radius, or about 384,400 kilometers.

How this lunar recession took place has been very controversial, because it is sensitive to many details. For one thing, tidal interaction is proportional to the Earth-moon distance to the sixth power. So, when the moon was located only at three times Earth’s radius, tidal interaction would have been about eight orders of magnitude greater. Making the problem even more challenging is the fact that what the early Earth and moon looked like were quite likely very different from the present day.

Will CLOE be able to answer some of these questions?

Korenaga: The complete picture of the early tidal evolution of the Earth-moon system will emerge only by a collaboration between geodynamics, which I do, and orbital dynamics, which the scientists at Southwest Research Institute do. It is extremely exciting to have this interdisciplinary collaboration.

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