Scientists have mapped over a thousand small mare ridges on the Moon, revealing ongoing contraction and potential seismic activity. These features, among the youngest on the lunar surface, form in the dark maria plains and share origins with known moonquake sources. The findings could guide safer landing sites for future missions like Artemis.
Researchers from the National Air and Space Museum's Center for Earth and Planetary Studies have produced the first comprehensive map of small mare ridges (SMRs) across the Moon's maria, the dark basaltic plains visible from Earth. Published in The Planetary Science Journal, the study identifies 1,114 previously unrecognized SMR segments, bringing the total known to 2,634. These ridges average 124 million years old, aligning closely with the 105-million-year average age of lobate scarps in the lunar highlands.
Unlike Earth, which features plate tectonics driving continental drift and volcanism, the Moon's single crust experiences internal stress from cooling and contraction. This process, first evidenced in 2010 by co-author Tom Watters, generates compressional forces that thrust sections of crust upward, forming both lobate scarps in highlands and SMRs in maria. The ridges often connect seamlessly between these regions, indicating a unified tectonic mechanism.
"Since the Apollo era, we've known about the prevalence of lobate scarps throughout the lunar highlands, but this is the first time scientists have documented the widespread prevalence of similar features throughout the lunar mare," said Cole Nypaver, the study's lead author and a postdoctoral research geologist.
The discovery expands known moonquake risks beyond highlands to maria, where Apollo missions landed. Watters linked lobate scarps to past seismic events; SMRs, formed similarly, suggest new hotspots. "Our detection of young, small ridges in the maria, and our discovery of their cause, completes a global picture of a dynamic, contracting moon," Watters noted.
As lunar exploration advances with NASA's Artemis program, understanding these tectonics aids in selecting stable sites. "A better understanding of lunar tectonics and seismic activity will directly benefit the safety and scientific success of those and future missions," Nypaver added.
