WASHINGTON, DC.- A new study co-led by the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum and the University of Maryland reveals that surface changes near the location of the Apollo 17 landing site, in the form of landslides and boulders rolling down slopes, resulted from strong moonquakes. The paper, published in Science Advances, shows the possibility that future moonquakes could cause new thrust faults, the type of faults that produce escarpments, to form on the surface of the moon, and existing fault scarps to grow. These moonquakes could pose a potential hazard to exploration and long-term outposts and infrastructure on the moon.

The moonquakes resulted from formation and subsequent activity along a relatively young thrust fault crossing the Taurus-Littrow Valley floor, the site of the last Apollo mission in 1972. The fault resulted from the shrinking moon contraction and tidal forces that cause thrust faults all over the moon. The team’s modeling shows that a moonquake, possibly caused by the Lee-Lincoln fault rupture about 90 million years ago, triggered a landslide on South Massif that sent material across the Taurus Littrow valley floor.

“An exciting implication of our study is that seismic shaking, caused by moonquakes generated by movement on young faults like the Lee-Lincoln fault, probably result in landslides and boulder falls all over the moon,” said Tom Watters, Smithsonian senior scientist emeritus and co-author of the paper.

Watters and co-author Nicholas Schmerr, an associate professor in the Department of Geology at the University of Maryland, concluded that the Lee-Lincoln fault scarp resulted from multiple co-seismic slip events of magnitude ~2.9 to 3.4 that occurred over the past tens of millions of years. The Lee-Lincoln fault scarp is one of thousands of such fault scarps that have been found in high-resolution images obtained by the Lunar Reconnaissance Orbiter Camera onboard the Lunar Reconnaissance Orbiter.

The finding suggests that other young thrust fault scarps developed and grew due to multiple co-seismic events. If a slip event on the Lee-Lincoln fault—generating a shallow moonquake of the magnitude estimated here—had occurred during the Apollo 17 mission, the lunar module could have sustained a level of seismic shaking that could have put the astronauts at risk. However, the probability of a strong quake occurring on a day in the Taurus-Littrow valley when the Apollo astronauts were on the moon is very small, estimated at about 1 of 20,000,000. Future missions with higher aspect ratio landers, or landers that are much taller than the width of their base, would require much less ground motion or shaking to threaten their stability.

“When planning the location and assessing stability of permanent outposts on the moon, the distribution of young thrust faults such as the Lee-Lincoln fault should be considered, as there is potential for still active and new thrust faults to form from ongoing contraction,” Watters said.

Watters is a senior scientist emeritus in the Center for Earth and Planetary Studies and a co-investigator on the Lunar Reconnaissance Orbiter Camera (Mark S. Robinson is the principal investigator). This research was funded by NASA’s Lunar Reconnaissance Orbiter mission, launched June 18, 2009. The Lunar Reconnaissance Orbiter is managed by the NASA Goddard Space Flight Center for the Science Mission Directorate.