Kamal Ghorui
Moonquake sensing could move into a new phase as fibre-optic technology is adapted for use on the lunar surface. The Moon, often perceived as still and unchanging, continues to experience internal vibrations caused by tidal interactions with Earth, meteorite impacts, and temperature extremes. Since the time of the Apollo missions, instruments have detected thousands of seismic events, yet their limited placement has left gaps in understanding how these movements behave across the entire lunar interior. Recent work associated with Los Alamos National Laboratory explores whether fibre-optic cables could provide a broader and more continuous way of detecting these vibrations. In connection with ongoing lunar exploration efforts led by NASA, this approach may contribute to safer and more informed mission planning.
Apollo missions and the first direct recordings of lunar seismic activity
Seismic experiments conducted by the Apollo missions resulted in the first direct measurements of moonquakes. Devices were set up at different landing locations, and the experiments were conducted between 1969 and 1977, resulting in the realisation that the Moon has several different tremors despite not having tectonic plates.The different types of seismic activity on the Moon are caused by a number of different factors, including the gravitational pull of the Earth, the expansion and contraction of the Moon due to temperature changes, and the impact of debris in space. Although the information collected in this period was valuable, the limited number of devices meant that a full picture of the seismic activity globally could not be obtained.
What is fibre-optic sensing using distributed acoustic sensing
Fibre-optic sensing relies on a method known as distributed acoustic sensing, where laser pulses travel through a cable and reflect in response to minute disturbances. Each vibration along the cable slightly alters the returning signal, allowing movement to be detected along its full length rather than at a single point.This transforms one cable into a long chain of virtual sensors. Instead of deploying multiple individual instruments across the lunar surface, a single extended cable could capture seismic activity over large distances. The concept reduces system complexity while expanding the range of data collected from a given area.
Fibre-optic cables under lunar conditions
Fibre optic cables provide a different avenue for tackling this problem. On Earth, fibre optic cables are usually buried in order to prevent interference from external sources. However, on the Moon, where there is no atmosphere and hence no weather-related interference, it is possible to place these cables on the Moon’s surface. Tests on fibre optic cables placed on simulated Moon surfaces, such as crushed basalt, have been conducted to assess their performance in detecting vibrations. According to research findings published in scientific journals such as Icarus and Earth and Space Science, fibre optic cables can be used to detect seismic activity on the Moon’s surface.
Technical considerations and constraints
The process of designing such systems is a balance of sensitivity and mass. While thicker cables made of fibre optics can offer clearer and more powerful signals, they can also make the system heavier. In space exploration missions, the cost of launching the systems is a major concern and is closely controlled.
