AI-powered digital elevation models reveal moon’s lobate scarps near Chang’e-6 landing site

A research team led by Prof. Di Kaichang from the Aerospace Information Research Institute (AIR) of the Chinese Academy of Sciences has developed an innovative method to enhance the study of lobate scarps—small reverse fault landforms thought to reflect ancient tectonic activity on the moon.

Utilizing an AI technique known as a generative adversarial network (GAN), the team combined high-resolution imagery from NASA’s Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) with lower-resolution digital elevation model (DEM) data to create pixel-scale DEMs at a two-meter resolution.

This new method is not limited by the coverage constraints of NAC-derived digital terrain models (DTMs) and reveals details about the shape and origin of these features, providing fresh insights into the moon’s evolutionary history.

This study, published in Icarus, challenges the traditional lunar magma ocean (LMO) model theory, which posits that the moon’s early surface was formed from a magma ocean just a few hundred kilometers deep. Instead, the results support an alternative theory known as the initially totally molten (ITM) model, which suggests that the moon began its existence entirely molten.

The study focused on 18 lobate scarps located approximately 300 km northwest of the Chang’e-6 landing site within the moon’s Apollo basin.

By integrating advanced geological modeling with crater size-frequency distribution measurements, the researchers discovered that these scarps were formed by intense horizontal pressures exceeding 400 megapascals within the last 80 million years.

These forces likely resulted from the moon slowly shrinking as it cooled, a process consistent with the ITM model.

This theory proposes that the moon was once completely molten and later contracted as it solidified, leaving behind surface wrinkles like these scarps as evidence of its fiery past.

The GAN-based DEM generation technique demonstrated remarkable accuracy, with a root mean square error of only 0.75 meters when validated against high-resolution DTMs from the LROC NAC. This high precision enabled detailed three-dimensional morphological analysis of the lunar scarps, revealing an average dip angle of 22.95 degrees, a relief of 18.7 meters, and a horizontal displacement of 46.5 meters.

Notably, the calculated displacement-length ratio of 3.80% significantly exceeds values previously documented for similar tectonic features on Mars and Mercury, highlighting the unique deformation characteristics in the studied lunar regions.

Age dating through buffered crater counting, combined with two chronological functions, indicated that the lunar scarps formed between 52.8 and 74.9 million years ago, with an average age of 59.3 million years.

These findings support the ITM model, which predicts ongoing tectonic activity driven by the moon’s continual thermal contraction and cooling. Conversely, the results challenge the LMO model’s premise that large-scale magmatic activity ceased early in the moon’s history.

Furthermore, the study integrated isotopic data from Chang’e-6 samples, revealing that the 2.8-billion-year-old (Ga) basalts are depleted in KREEP—a geochemical component rich in potassium (K), rare earth elements, and phosphorus.

This finding undermines the hypothesis that radioactive decay contributed to prolonged magmatic activity as suggested by the LMO lunar evolution model.