Measuring titanium in Apollo rock to uncover moon's early chemistry
by Advik D. Vira, Emily First, The Conversation
Introduction
Earth and the moon may look very different today, but they formed under similar conditions in space. In fact, a dominant hypothesis says that the early Earth was hit by a Mars-sized object, and it was this giant impact that spun off material to form the moon. But unlike Earth, the moon lacks plate tectonics and an atmosphere capable of reshaping its surface and recycling elements such as oxygen over billions of years.
Understanding the Chemical Composition of the Moon
As a result, the moon preserves a record of the geological conditions that helped shape it and can give scientists insight into the world we live in today. Rocks that were formed during early volcanic activity on the moon offer a window into events that occurred nearly 4 billion years ago. By uncovering the conditions under which the moon's rocks formed, scientists move closer to understanding the origins of our own planet.
Research Overview
In a study published March 2026 in the journal Nature Communications, our team of physicists and geoscientists investigated ilmenite, a mineral composed of iron, titanium, and oxygen, in a moon rock crystallized from an ancient lunar magma. We used cutting-edge electron microscopy to probe the chemical signature of titanium in this ilmenite, finding that about 15% of the titanium carries less of an electrical charge than expected.
Implications of Trivalent Titanium
In ilmenite, an atom of titanium typically loses four electrons when bonding with oxygen, resulting in a positive charge of 4+, known as the atom's oxidation number. From the sample we studied, a rock collected during the Apollo 17 mission, we found that some of the titanium in ilmenite actually has a charge of only 3+, referred to as trivalent titanium. Our measurement of trivalent titanium confirms what geologists had long suspected: that some titanium in lunar ilmenite exists in a lower charge state.
Trivalent titanium occurs only when the amount of oxygen available for chemical reactions is low. Thus, the abundance of trivalent titanium in ilmenite could tell us about the relative availability of oxygen in the moon's interior when the rock formed, around 3.8 billion years ago.
A Link to the Moon's Early Chemistry
Our team has closely studied only one moon rock so far, but from published studies, we have identified more than 500 analyses of lunar ilmenite that could contain trivalent titanium. Studying these samples could reveal new details about how the moon's chemistry varies across different locations and time periods.
While our work highlights a link based on prior studies, the relationship between trivalent titanium in ilmenite and oxygen availability has not yet been quantified with targeted experimental data.
By conducting experiments that explore that link, ilmenite could reveal more details about the moon's interior. We also expect this relationship to apply to other planets and asteroids that don't contain much chemically available oxygen, relative to Earth.
Publication details
Advik D. Vira et al, Trivalent titanium in high-titanium lunar ilmenite, Nature Communications (2026). DOI: 10.1038/s41467-026-69770-w
Journal information: Nature Communications
Get Instant Summarized Text (Gist)
Analysis of ilmenite in an Apollo 17 lunar rock shows that about 15% of titanium exists in a trivalent (Ti3+) state, indicating low oxygen availability during the rock's formation around 3.8 billion years ago. This finding provides insight into the moon's early interior chemistry and suggests that further study of trivalent titanium in lunar samples could reveal more about planetary formation conditions.
This summary was automatically generated using LLM. Full disclaimer
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