Moonquake sensing may be moving to a new phase as fiber-optic technology is adapted for use on the lunar surface. The Moon, often considered stable and unchanging, continues to experience internal vibrations caused by Earth’s tides, meteorite impacts, and extreme temperatures. Since the Apollo missions, instruments have detected thousands of seismic events, yet their limited location has left gaps in our understanding of how these activities behave throughout the lunar interior. Recent work involving Los Alamos National Laboratory explores whether fiber-optic cables could provide a broader and more continuous way of detecting these vibrations. Regarding ongoing NASA-led lunar exploration efforts, this approach could contribute to safer and more informed mission planning.
Apollo mission and its first direct recording lunar seismic activity
Seismic experiments conducted by the Apollo missions resulted in the first direct measurements of the Moon’s earthquakes. Instruments were installed at various landing sites, and experiments were conducted between 1969 and 1977, resulting in the realization that the Moon has many distinct shocks, despite having no tectonic plates.The variety of seismic activity on the Moon is caused by many different factors, including Earth’s gravitational pull, the Moon’s expansion and contraction due to temperature changes, and impacts from space debris. Although the information collected over this period was valuable, a complete picture of seismic activity globally could not be obtained due to the limited number of instruments.
What is Fiber-Optic Sensing Using Distributed Acoustic Sensing
Fiber-optic sensing relies on a method called distributed acoustic sensing, where laser pulses travel through a cable and are reflected in response to minute disturbances. Each vibration along the cable slightly alters the returning signal, allowing motion to be detected along its entire length rather than at a single point.This turns a single cable into a long chain of virtual sensors. Instead of deploying many separate instruments on the lunar surface, an extended cable could pick up seismic activity over large distances. This concept reduces system complexity while expanding the range of data collected from a given area.
Fiber-optic cable under lunar conditions
Fiber optic cables offer a different way to deal with this problem. On Earth, fiber optic cables are usually buried to prevent interference from outside sources. However, on the Moon, where there is no atmosphere and hence no meteorological interference, it is possible to lay these cables on the lunar surface. Tests have been conducted on fiber optic cables laid over simulated lunar surfaces such as crushed basalt to assess their performance in detecting vibrations. Fiber optic cables could be used to detect seismic activity on the lunar surface, according to research findings published in scientific journals such as Icarus and Earth and Space Science.
Technical Considerations and Constraints
The process of designing such systems is a balancing of sensitivity and mass. While thicker cables made from fiber optics can provide clearer and more powerful signals, they can also make the system heavier. In space exploration missions, the cost of launching systems is a major concern and is closely controlled.