Cracks discovered in the surface of the Moon suggest that our nearest neighbour is shrinking.
Like a deflating balloon, the satellite is contracting as its interior cools, scientists believe.
The cooling has reduced the radius of the Moon by around 100m in the relatively recent lunar past, evidence indicates.
The cooling has reduced the radius of the Moon by around 100m in the relatively recent lunar past, evidence indicates.
The discovery was made after a probe captured images of unusual fault lines called "lobate scarps" in the lunar highlands.
Similar cracks were first seen in photos taken near the Moon's equator by astronauts on Apollo missions in the early 1970s.
Fourteen new lobate scarps have now been identified by the Lunar Reconnaissance Orbiter spacecraft, researchers reported in the journalScience. They were found mainly in the highlands, showing that the lines are globally distributed.
Experts believe the cracks were created by rupturing of the brittle lunar crust as the moon shrank – a process that appears to be geologically recent.
"One of the remarkable aspects of the lunar scarps is their apparent young age," said Dr Thomas Watters, from the Smithsonian Institution in Washington DC.
"Relatively young, globally distributed thrust faults show recent contraction of the whole moon, likely due to cooling of the lunar interior.”
However, stargazers are unlikely to notice any change in the size of the moon in the near future.
The “relatively young” age of the faults indicates only that the 100m shrinkage occurred within the last billion years.
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