NASA says the moon is shrinking and generating 'moonquakes'

Quakes are occurring on the moon and it is shrinking as its interior cools, NASA says.

The moon has become about 50 metres thinner in the past several hundred million years, and because of its"brittle" surface crust, it is breaking and forming "thrust faults", a statement from NASA said.

The faults are usually tens of metres high and extend for miles.

"Our analysis gives the first evidence that these faults are still active and likely producing moonquakes today as the moon continues to gradually cool and shrink," Smithsonian National Air and Space Museum Centre for Earth and Planetary Studies senior scientist Thomas Watters said.

He said some quakes can be strong, and measure about five on the Richter scale.

Four seismometers were placed on the moon by astronauts during the 1970s to pinpoint quake locations. NASA now hopes to compare specific fault regions, to see if there is any evidence of more recent moonquake activity.

"Establishing a new network of seismometers on the lunar surface should be a priority for human exploration of the moon, both to learn more about the moon's interior and to determine how much of a hazard moonquakes present," NASA Marshall Space Flight Center planetary seismologist Renee Weber said.

NASA says evidence of active faults also came from pictures of the moon from its Lunar Reconnaissance Orbiter (LRO) spacecraft.

"It's really remarkable to see how data from nearly 50 years ago and from the LRO mission has been combined to advance our understanding of the moon while suggesting where future missions intent on studying the moon's interior process should go," NASA Goddard Space Flight Center LRO project scientist John Keller said.

NASA is planning to return astronauts to the moon by 2024.