The moon is shrinking but it will not be disappearing any time soon and its shrinkage will not affect the earth in any way, astronomers say.
Reporting on Thursday in the US journal Science, the astronomers said they had found previous undetected landforms which indicate that the earth's satellite has been shrinking but by only a tiny amount.
Relative to the moon's age, estimated at around 4.5 billion years, the contraction is recent, occurring less than a billion years ago, and is measured at about 100 metres.
Thomas R Watters of the Centre for Earth and Planetary Studies at the Smithsonian's National Air and Space Museums said scientists have identified 14 landforms called lobate scarps scattered over the surface of the moon.
The scarps had previously been noted at the moon's equator, but this is the first evidence in other areas, indicating they result from a global process.
Dr Francisco Diego, a fellow of the Royal Astronomical Society in London, agreed with his US colleagues, saying the shrinking was "almost negligible".
"It is an interesting fact to see how these objects in the solar system develop and evolve for us to know ... the origins of these bodies and how they are behaving," he told Al Jazeera.
No large craters
The Science study calls the scarps "evidence of recent thrust faulting on the moon". But this is planetary science, where "recent" can mean a billion years ago.
The scarps, or cliffs, extend across some small craters, and small craters tend to be obliterated over time, Watters said.
In addition, there are no large craters imposed on top of the scarps, another indication they are relatively recent, in planetary terms, he said.
"One of the really cool parts of this ... the faults are so young-looking that you can't escape the possibility that this contraction occurred recently, and could indicate that the moon is still active," he said.
The size of the scarps indicates a shrinkage in the size of the moon of about 100 metres, which would not be nearly enough to be noticed with the naked eye. The moon is about one-fourth the size of the earth in diameter.
The scarps range up to 10 metres high and a few kilometers long, according to Watters.
By comparison, the planet Mercury has much larger scarps indicating considerably more shrinkage over time.