The Moon, Earth's constant companion for billions of years, is slowly shrinking. That is the striking conclusion of a study published in The Planetary Science Journal in October 2026, which found more than 10,000 young faults on the lunar surface linked to the Moon's gradual cooling and contraction.
According to the research, the Moon's radius has shrunk by about 45 metres over the past 400 million years — a tiny change on a planetary scale, but one that is reshaping the lunar surface, triggering moonquakes, and offering scientists a new window into how rocky worlds age.
Indian researchers, including scientists at Ahmedabad's Physical Research Laboratory, have been at the forefront of explaining what the findings mean, and their own work on lunar dust adds a fascinating twist: even as the Moon shrinks, it may be gaining mass.
The new study is based on images from NASA's Lunar Reconnaissance Orbiter Camera, which has spent years mapping the Moon's surface in extraordinary detail. By analysing those images, researchers identified thousands of small, cliff-like landforms known as lobate scarps — wrinkles in the lunar crust formed when the surface is compressed and breaks.
These scarps are the fingerprints of contraction: as the Moon's hot interior gradually cools, the whole body contracts, much like a grape drying into a raisin, and the brittle crust buckles and fractures. The study estimates that the Moon has contracted by 42 to 46 metres — roughly 148 feet — over the past 400 million years, at a rate of about 6 to 11 centimetres per million years.
That rate sounds almost imperceptibly slow, and on human timescales it is. But over geological time it adds up, and it has real consequences. When the crust slips along these young faults, it can generate moonquakes — tremors that, unlike earthquakes on Earth, are not confined to plate boundaries.
The Moon has a single-plate structure, so faults and moonquakes can occur across its entire surface, and the new catalogue of more than 10,000 young faults suggests that the Moon is far more geologically active than its still, silent appearance suggests.
For future lunar missions, including crewed landings planned under NASA's Artemis programme and India's own Chandrayaan programme, understanding where these faults are and how active they might be is a matter of practical safety as well as scientific curiosity.
Professor Jayesh Pabari, a planetary science expert at the Physical Research Laboratory in Ahmedabad, has been explaining the findings to Indian audiences, and his own research adds another layer to the story. In conversation with Divya Bhaskar, Pabari described how satellite images had revealed the Moon's gradual shrinking through the small scarps and ridges on its surface, and he linked the contraction to the steady loss of heat from the lunar interior.
As the Moon cools, he explained, the material on its surface — soil and dust — is gradually compressed, and the body contracts.
But Pabari's research, conducted using impact theory and first reported in 2020, reveals a second, seemingly paradoxical process happening at the same time. The Moon has no atmosphere to burn up incoming debris, so interplanetary dust particles — extremely fine solid particles floating in the space between planets — reach its surface directly and accumulate there. At the same time, impacts on the lunar surface eject dust particles, and sometimes even ice, back into space.
By tracking the particles arriving and leaving, Pabari and his team found that more material arrives than escapes. The result, he says, is that the Moon is gradually gaining mass even as it shrinks in size — a conclusion that sounds contradictory but follows from the physics: contraction reduces volume, while the steady rain of cosmic dust adds weight.
The escaping ice is of particular interest. Water ice is considered one of the most valuable resources for future lunar exploration, because it could potentially be converted into drinking water, oxygen and even rocket fuel, supporting long-duration human presence on the Moon.
If impacts are constantly ejecting some of that ice into space, understanding the balance between ice lost and ice gained matters for mission planners choosing where to land and what resources to rely on. Pabari's team was the first to report the lunar escape process in detail, and their work has helped frame how scientists think about the Moon as a dynamic system rather than a dead rock.
The shrinking-Moon findings also connect with a separate line of Indian research on lunar ice. Scientists from the Physical Research Laboratory, working with data from the Chandrayaan-2 orbiter, have identified strong evidence of subsurface ice in some of the coldest craters near the Moon's south pole.
Using the orbiter's Dual Frequency Synthetic Aperture Radar — the first fully polarimetric synthetic aperture radar to study the Moon in both L-band and S-band frequencies — researchers found distinctive radar signatures in a small crater within the larger Faustini crater, suggesting a mixture of ice and soil beneath the surface.
The south pole's permanently shadowed craters, where temperatures can fall below minus 200 degrees Celsius, are among the coldest places in the solar system, and they are considered prime targets for future missions precisely because ancient ice can remain stable there for billions of years.
Taken together, these threads paint a picture of a Moon that is far from static. It is cooling and contracting, cracking along thousands of young faults, trembling with moonquakes, shedding dust and ice into space, and at the same time gathering new dust from the solar system.
None of this poses any danger to Earth: the changes unfold over millions of years, and the Moon's influence on tides, on the stability of Earth's axis and on the rhythms of life will continue essentially unchanged for the foreseeable future. But for scientists, the Moon's slow transformation is a gift — a nearby laboratory for understanding how planets cool, how their surfaces evolve, and how the resources that future explorers will depend on are distributed and preserved.
For India, the research carries a particular resonance. From Chandrayaan-1's discovery of water molecules on the lunar surface to Chandrayaan-2's radar mapping of polar ice and the Physical Research Laboratory's work on lunar dust, Indian scientists have played a growing role in lunar science.
The shrinking-Moon study, led by international teams but interpreted and extended by Indian researchers, is another chapter in that story — and a reminder that some of the most profound discoveries about our nearest neighbour are still being made, one fault line at a time.
(Reporting based on The Planetary Science Journal study as reported by Divya Bhaskar and Shankar IAS Parliament, and ISRO's Chandrayaan-2 findings.)