Chemical Signature Hidden in Lunar Rocks Hints at Oxygen in The Ancient Moon : ScienceAlert

Today, Earth and the Moon appear quite distinct, yet they originated under similar space conditions. A prevalent theory suggests that a Mars-sized body collided with early Earth, resulting in a massive impact that created the Moon from the debris.

Unlike Earth, the Moon does not possess plate tectonics or an atmosphere that could transform its surface and recycle elements like oxygen over billions of years. Consequently, the Moon retains a record of its formative geological conditions, offering scientists insights into our current world.

The rocks formed from early volcanic activity on the Moon provide a glimpse into events from nearly 4 billion years ago. By analyzing the conditions under which these rocks originated, scientists gain a better understanding of Earth’s beginnings.

A recent study published in March 2026 in the journal Nature Communications reveals that a team of physicists and geoscientists examined ilmenite—a mineral made of iron, titanium, and oxygen—found in a Moon rock formed from ancient lunar magma. Utilizing advanced electron microscopy, the team identified that around 15% of the titanium in the ilmenite has a lower electrical charge than anticipated.

Implications of trivalent titanium

In ilmenite, titanium atoms usually lose four electrons when they bond with oxygen, resulting in a positive charge of 4+, known as the oxidation number. Analysis of a sample collected during the Apollo 17 mission revealed that some titanium atoms have a charge of only 3+, known as trivalent titanium. This measurement supports geologists’ long-held suspicions that some titanium in lunar ilmenite is in a reduced charge state.

Trivalent titanium forms only when there is a low oxygen availability for chemical reactions. Therefore, the amount of trivalent titanium in ilmenite could provide insights into the oxygen levels in the Moon’s interior when the rock formed around 3.8 billion years ago.

A link to the Moon’s early chemistry

Although the team has examined only one Moon rock, they have identified over 500 published analyses of lunar ilmenite that might contain trivalent titanium. Studying these samples could offer new insights into how the Moon’s chemistry varies across locations and over time.

While the research highlights a possible link, the relationship between trivalent titanium in ilmenite and oxygen availability has yet to be precisely quantified through targeted experiments. By conducting such experiments, ilmenite could provide additional details about the Moon’s interior. This relationship is also expected to be applicable to other planets and asteroids with limited chemically available oxygen compared to Earth.

What’s next?

This approach can be applied to numerous Moon rocks collected during the Apollo missions more than 50 years ago, as well as future samples from the upcoming Artemis missions or rocks from the Moon’s far side returned in 2024 by China’s Chang’e-6 mission. A team member plans to use their new experimental lab to study how oxygen availability in magma influences trivalent titanium abundance in ilmenite. With such experiments building on current findings, ilmenite could potentially reconstruct the history of ancient lunar magmas.

Related: The Mystery of Intense Magnetism on The Moon Is Finally Solved

The team believes that future lunar rock studies using advanced scientific methods are crucial for uncovering the chemical conditions that existed on the ancient Moon. These findings could shed light not just on the Moon’s history but also on the earliest chapters of Earth’s past—records that have since been erased from our planet.

Advik D. Vira, Graduate Student in Physics, Georgia Institute of Technology and Emily First, Assistant Professor of Geology, Macalester College

This article is republished from The Conversation under a Creative Commons license. Read the original article.