Weighing seismic risks at Artemis landing sites

Planetary scientists at Hyderabad’s National Geophysical Research Institute warn that the lunar south pole region (LSPR), which NASA plans to use as landing sites for human and robotic Artemis missions, is prone to seismic hazards.

“Our study¹ suggests seismic hazard in LSPR is more widespread than previously thought,” says Senthil Kumar, principal scientist at NGRI, and corresponding author of research to gauge how safe are the landing sites for Artemis missions.

NASA has identified 13 candidate landing regions within 6° latitude from the lunar south pole.

Kumar, and research scholar Abhisek Mishra, used high-resolution images from NASA’s Lunar Reconnaissance Orbiter spacecraft to discover a large number of unidentified “seismically active thrust faults” near the Moon’s south pole.

Known as lobate scarps, “these are one of the primary sources of lunar seismicity capable of producing magnitude 3.5–6.5 shallow moonquakes at focal depths of 5–10 km,” they report.

“Our geological mapping led to the discovery of 75 new lobate scarps consisting of 532 segments at 30 sites, while previous work traced only 32 lobate scarps and 172 segments at 20 sites,” the report says.

Kumar and Mishra’s study revealed that all 141 scarps were formed over the last 100 million years.

Looking at the likely occurrence of magnitude 1–4 shallow moonquakes along these scarps in the next few decades, the researchers noted potential seismic hazard zones and seismically low risk areas at the Artemis candidate landing regions. A map was created of seismic hazard buffer zones around the lobate scarps.

“We measured the lengths, depths and orientations and — for the first time — the movement directions of all the faults,” Kumar told Nature India. “The measurements suggest that most faults moved toward the south pole. We calculated the depth of faults beneath the scarp segments and the maximum size of potential shallow moonquakes.”

The researchers said they determined the ages of more than 140 fault segments, “forming the largest dataset produced thus far”. Their ages revealed that the faults had grown at a rate of about 1-km per million years (similar to those continental faults on Earth) and the tectonic activity in the LSPR occurred continuously in the last 100 million years.

They also analyzed the relative positions of the Artemis candidate landing regions with respect to the seismic hazard buffer zones and the potential seismic risks associated with these regions.

“Our seismic hazard analysis suggested that all 13 Artemis sites are unlikely to be affected by 1-3 magnitude moonquakes, while a few of them could be affected by 4 magnitude moonquakes, depending on various hazard scenarios,” the authors said. “At least five sites around Shackleton crater, and two near Malapert Mountain, are most likely to have low seismic hazard and suitable for long-term settlement”.

“We believe our results should prompt new site-specific seismic hazard assessment for the landing regions. More robust site-specific probabilistic seismic hazard analysis is required for each site before astronauts land there and critical infrastructure is established.”

“Potential seismic risks at the Artemis candidate landing regions is a fundamental contribution to understanding the tectonics of the Moon,” James Head, distinguished professor of Geological Sciences, at Brown University says. “Most importantly, it has extreme relevance to global plans for the longer-term exploration and settlement of the south polar region of the Moon, where it is thought that buried water resources might exist”.