More than 10,000 young faults put the moon's shrinkage at about 45 meters
Smithsonian-led researchers mapped over 10,000 young lunar faults and estimate the moon shrank about 45 meters over 400 to 800 million years. Because the moon is a single plate, the faults are spread across its surface and moonquakes can start anywhere.
The Scientist · Science desk
Key figures: about 1.7 micrometers of radius change across 17 years of Lunar Reconnaissance Orbiter imaging; about 0.1 micrometers of radius loss a year; and at least 6, up to 11, centimeters of radius loss per million years, if the rate stayed constant.
| Figure | Value | Note | Claim |
|---|---|---|---|
| Radius change over 17 years of LRO imaging, about | 1.7 micrometers | 14 | |
| Yearly radius loss, about | 0.1 micrometers | 5 | |
| Radius loss per million years, at least | 6 cm | up to 11 cm, if the rate was constant | 5 |
What happened
- The paper, titled 'Thrust Faulting and the Late-Stage Contraction of the Moon', appeared Oct. 14 in The Planetary Science Journal.
- The team mapped lobate scarps and small mare ridges, both contractional landforms, across the lunar highlands and the dark maria using Lunar Reconnaissance Orbiter Camera images.
- If the radius loss stayed constant, the figure works out to about 6 to 11 centimeters per million years, or roughly 0.1 micrometers a year.
- The paper suggests widespread faulting came late because a thick, fractured, porous early crust insulated the interior and held back cooling and contraction.
Why it matters
- What it limits constraint At this rate, 17 years of orbiter imaging spans only about 1.7 micrometers of radius change, so the 45 meters rests on landforms and an age window, not on observed change.
- What doesn't add up contradiction PopSci says astronomers now know how fast the moon is contracting, but the paper's rate is conditional on a constant pace across a 400 to 800 million year window.
- Who's exposed exposure Thick-crust terrain has the fewest faults and may be the most stable ground, and PopSci reports quake distribution and frequency may inform NASA's long-term lunar planning.
Divide 45 meters by each end of the dating window and the paper's rate falls out: 5.6 centimeters per million years at 800 million years, 11.25 at 400 million [13]. The stated 6 to 11 is, to rounding, that division, so the spread in the rate is the factor of two in the faults' age carried through [13]. The coverage does not give an uncertainty on the 45 meters itself, or say which earlier estimate this one improves on. The phys.org account, provided by the National Air and Space Museum, calls the study the most detailed estimate yet [16].
That account sets the number against Earth, where plates move about 1.5 centimeters a year [6]. That is 15,000 micrometers, roughly 150,000 times the moon's 0.1 micrometers of radius loss a year [15]. The two quantities differ: sideways plate drift on one side, a shrinking radius on the other. We'd treat the ratio as a sense of scale, not a like-for-like rate.
The geometry explains why the faults are everywhere. On Earth, plate boundaries localize about 90% of tectonic and seismic activity [7]. The moon is a single-plate body whose faults express contraction, so they are widely distributed, and moonquakes from slip on existing faults or from new faults forming can occur anywhere [7].
Thomas Watters, who led the study and is scientist emeritus at the museum's Center for Earth and Planetary Studies, said: "The number of these young faults revealed in LROC images is much greater than I ever imagined." [3][11] He added: "As the interior of the moon continues to cool and contract, it is expected that the growth of existing faults and formation of new faults continues today." [12]
The second sentence is an expectation drawn from continued cooling. The more than 10,000 faults are the ones already in the images [1].
What to watch
- Whether follow-up work puts an uncertainty on the 45 meters or narrows the 400 to 800 million year age window that sets the rate range.
- Whether new fault growth, which Watters expects to continue today, shows up in later orbiter images or moonquake records.
- Whether NASA surface planning adopts fault density, including the low counts over thick crust, as a siting input.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence62
- Adoption
- Not scored
- Hype gap+15
- Incentives30
- Confidence65
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
The paper, 'Thrust Faulting and the Late-Stage Contraction of the Moon', was published Oct. 14 in The Planetary Science Journal and identifies more than 10,000 young faults distributed across the moon's surface.
- [2]
The study estimates that the moon's radius has decreased by approximately 45 meters (148 feet) over the past 400 to 800 million years.
- [3]
The study was led by Thomas R. Watters, scientist emeritus in the Center for Earth and Planetary Studies at the Smithsonian's National Air and Space Museum, with co-authors Maria Banks, Cole Nypaver and Mark Robinson.
- [4]
Using Lunar Reconnaissance Orbiter Camera (LROC) observations, the researchers mapped contractional landforms known as lobate scarps and small mare ridges across both the lunar highlands and the maria.
- [5]
If the rate of radius decrease has remained constant over this period, the moon has been shrinking about 6 to 11 centimeters per million years, or about 0.1 micrometers per year.
- [6]
Earth's plates move at an average rate of about 1.5 centimeters per year, driven by heat loss from Earth's interior.
- [7]
Earth's plate boundaries localize about 90% of the planet's tectonic and seismic activity; the moon is a single-plate body with faults that express contraction, so faults are widely distributed and moonquakes from slip on existing faults or formation of new faults can occur anywhere.
- [8]
The thickest lunar crust appears to have the fewest faults, suggesting these areas may be the most stable.
- [9]
The paper suggests widespread faulting did not occur early in lunar history because a heavily fractured, thick, porous crust insulated the interior, inhibiting cooling and contraction until relatively recently.
- [10]
The Lunar Reconnaissance Orbiter has been orbiting the moon for 17 years, and the LROC has returned millions of images of the lunar surface.
- [11]
"The number of these young faults revealed in LROC images is much greater than I ever imagined," Watters said.
- [12]
"As the interior of the moon continues to cool and contract, it is expected that the growth of existing faults and formation of new faults continues today."
- [13]
Dividing 45 meters by the ends of the 400 to 800 million year window gives 11.25 and 5.6 centimeters per million years, matching the reported 6 to 11; the spread in the rate equals the factor of two in the age window.
- [14]
At 0.1 micrometers per year, 17 years of LRO imaging spans about 1.7 micrometers of radius change.
- [15]
Earth's plate speed of 1.5 centimeters a year is 15,000 micrometers a year, about 150,000 times the moon's 0.1 micrometers a year of radius loss.
- [16]
The phys.org account, provided by the National Air and Space Museum, says the study offers the most detailed estimate yet of how much the moon has contracted as its interior cooled.
- [17]
PopSci writes that astronomers now know how fast the moon is contracting.
- [18]
PopSci says the distribution and frequency of moonquakes may help NASA better plan for a long-term human presence on the moon.
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Sources
3 independent publishers whose own reporting we read for this story.
- gizmodo.comNASA Images Reveal 10,000 Young Faults on the Moon. That’s a Problem
1 article · October 15, 2026
- phys.orgLunar fault maps reveal how much the moon is shrinking
1 article · October 15, 2026
- popsci.comThe moon is shrinking. Astronomers finally know how fast.
1 article · October 14, 2026
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