"We think it's very likely that these eight quakes were produced by faults slipping as stress built up when the lunar crust
was compressed by global contraction and tidal forces, indicating that the Apollo seismometers recorded the shrinking moon and the moon is still tectonically active," explains Wafters.
Signs of such an impact should be visible in the structure of the lunar crust
But since the lunar crust
is brittle, it breaks and produces thrust faults, where one section of crust is pushed up over another.
The magma that produced those beads had emerged from the depths of the lunar mantle, travelled up through the lunar crust
, and been hurled to the airless surface of the Moon by a fire fountain-type volcano, similar to the ones found on Earth.
According to the analysis of seismic data, the internal structure of the moon can be roughly divided into a lunar crust
, lunar mantle, and lunar nucleus.
These discoveries provide a new tool to unravel the processes involved in the formation of the Moon, how the lunar crust
cooled, and its impact history.
Among the discoveries: The lunar crust
is much thinner and more battered than scientists had imagined.
Accordingly, these domes might be interpreted as surface manifestations of laccolithic intrusions formed by flexure-induced vertical uplift of the lunar crust
(or, alternatively, as low effusive edifices due to lava mantling of highland terrain, or kipukas, or structural features).
The lunar crust
is also far more fractured by impacts than anyone had suspected; a full 12 percent of the surface layer is nothing but empty space in churned-up rock deposits.
The probes are designed to precisely map the moon's gravity so scientists can learn what lies beneath the lunar crust
and whether the moon's core is solid, liquid or some combination of the two.
US scientists have analysed ancient samples of lunar crust
derived from the molten rock that gave birth to the Moon.