The 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.
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.
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.
This illustration shows the rock on the Moon, as well as an atomic image of the sample’s crystal structure and a representation of the chemical signature of trivalent titanium.
August Davis
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.
The left image shows a scanning electron microscopy image of the lunar rock investigated in this study. Regions with titanium are shown in light blue. The white boxes show areas where the team extracted samples to analyze ilmenite. The right image shows a transmission electron microscopy image of the extracted ilmenite. The inset shows a zoomed-in view where you can see individual columns of iron and titanium.
Advik Vira
A link to the Moon’s early chemistry
Since it is the ilmenite, not the study, that contained trivalent titanium, I would recast the previous sentence as follows:…
