The Moon is shrinking. What happens when its surface can’t take the pressure?

If you are a moon person, you love to stare at it every night. You stand by your window or balcony and just look at the celestial body. You observe its dark spots and some days you just stare at the beauty of it. We all know about the phases of the moon and know how it appears dark when no sunlight bounces off its lunar surface. But have you ever noticed that the moon is shrinking in size?

If you look at the Moon tonight, you may feel that it is not true; the Moon is not shrinking. Its familiar dark patches remain visible and its outline looks unchanged and exactly where you see it every day.

However, satellite photographs of the Moon and its lunar orbit are an entirely different story. In the pictures of the moon you can see the the surface which has small cliffs. These are places which are marked where the crust has broken and moved. According to a Smithsonian-led study these crusts are connected to the Moon’s gradual contraction.However, the change is extremely slow and not noticeable from your balcony or terrace. On the surface itself, however, that slow squeeze can have consequences.

Why is the Moon shrinking?

The Moon’s interior still holds heat. As it gradually cools, it contracts. Its outer crust cannot simply stretch or fold smoothly to accommodate the smaller interior. The surface is brittle, so pressure can make it break.

Picture an apple developing wrinkles as it dries. This comparison can be one way to explain the contraction, although the Moon’s rocky surface is different and it responds by forming faults.

Along some faults, one section of crust is pushed up over another. The resulting small cliffs are called lobate scarps. Is you see it from afar, they resemble steps across the landscape.

How much smaller has the Moon become?

The study, published October 14 in The Planetary Science Journal, estimates that the Moon’s radius decreased by approximately 45 metres over the past 400 million to 800 million years. The radius is the measurement from the centre to the surface.

Assuming a constant rate, that works out to roughly six to 11 centimetres per million years. Scientists are measuring an extremely slow geological process, rather than a sudden change.

The research team, led by Thomas Watters of the Smithsonian’s National Air and Space Museum, identified more than 10,000 young faults using Lunar Reconnaissance Orbiter Camera observations.

What happens when the lunar surface moves?

Scientists have found out that movement along faults can produce moonquakes. Apollo astronauts placed instruments on the Moon that recorded seismic activity. Those measurements established that the lunar ground does shake.

Not every moonquake comes from contraction. Earth’s gravitational pull can cause deep moonquakes. Impacts provide another source of vibrations.

The shrinking process is associated with shallower events, where movement closer to the surface can generate substantial shaking. A fault does not necessarily move continuously. Slow pressure can build before rock suddenly slips.

Could moonquakes affect future lunar bases?

To observe the moonquakes, the location of the base matters. NASA-funded research has identified faults near the lunar south pole, an important region for exploration. Modelling suggests that movement along some faults could produce strong local shaking.

Researchers also found that certain slopes could be vulnerable to landslides, including under relatively light shaking. The practical question is where to place structures and equipment. Mapping faults helps planners understand possible hazards before committing to a location.

A shrinking Moon does not make every landing site unsafe. Risks depend on the surrounding terrain and nearby fault activity.

Is the Moon disappearing?

No. It is contracting but that does not say that it can vanish or break apart. For now, it is going to be the same. However, people who are watching from Earth, you cannot rule out that it will change some day especially when scientists have been saying that the Moon remains geologically active. People who are planning to build infrastructure there need to understand this activity more closely.