Analysing gravity data collected by spacecraft orbiting the moon reveals groundbreaking insights about the Moon-s deep internal structure without having to land on the surface. The study offers evidence that a warmer interior on the Moon-s near side compared to the far side created the conditions for volcanic activity, that may have lasted far longer than expected. The findings have been published in the scientific journal Nature by researchers from NASA, University of Arizona, University of California and TU Delft.
In the lunar study, published May 14 in the journal Nature, researchers developed a new gravity model of the Moon that includes tiny variations in the celestial body-s gravity during its elliptical orbit around Earth. These fluctuations cause the Moon to flex slightly due to Earth-s tidal force - a process called tidal deformation - which provides critical insights into the Moon-s deep internal structure.
Lunar Asymmetry
The study looked at gravitational changes to the Moon-s near and far sides. While the near side is dominated by vast plains - known as mare - formed by molten rock that cooled and solidified billions of years ago, the far side is more rugged, with few plains.
Some theories suggest the Moon-s near-side plains are volcanic in origin, formed through internal heating from radioactive elements. The study offers the strongest evidence yet the volcanic activity is linked to a deep thermal anomaly in the Lunar nearside.
We found that the Moon-s near side is flexing more than the far side, meaning there-s something fundamentally different about the internal structure of the Moon-s near side compared to its far side.
Ryan Park, first author and supervisor NASA-s Solar System Dynamics Group at Jet Propulsion Laboratory
When comparing their results with other models, Park-s team found a small but greater-than-expected difference in how much the two hemispheres deform. The most likely explanation is that the near side has a warm mantle region, indicating the presence of heat-generating radioactive elements, which is evidence for volcanic activity that shaped the Moon-s near side 2 billion to 3 billion years ago.
Accelerated Modelling
This research was made possible in part by an open-source tool developed at TU Delft. Researcher Marc Rovira Navarro created the code, called LOV3D, which calculates how a non-spherical body deforms under tidal forces. Compared to earlier approaches, the new method is significantly faster, generating the tidal response resulting from different interior models in minutes instead of days.
This speed allowed the team to test a wide range of internal configurations and identify those consistent with observations from NASA-s GRAIL (Gravity Recovery and Interior Laboratory) mission. The mission-s twin spacecraft, Ebb and Flow, orbited the Moon between December 2011 and December 2012, collecting the gravity data used in the study.
It’s exciting to see this tool being used in such a fundamental study. I hope it will also contribute to future missions - particularly to icy moons with subsurface oceans. The code can help reveal variations in ice shell thickness, which is key to assessing their potential habitability. That-s something we are already exploring.
Dr. Marc Rovira Navarro, Assistant Professor Planetary Exploration
The paper was published on 14 May 2025 in Nature. You can read more about how gravity data is helping to explore planetary interiors on the NASA Jet Propulsion Laboratory website. Dutch newspaper Trouw interviewed Marc Rovira Navarro on the method for this article.
Dr. M. (Marc) Rovira Navarro
Assistant Professor
- M.RoviraNavarro@tudelft.nl
