Hello,

lunar mare basalt (e.g. sample 15015 https://www.lpi.usra.edu/lunar/samples/atlas/detail/?mission=Apollo%2015&sample=15016) shows many voids.

On earth this is due to volatilization of compounds when magma decompresses. Low viscosity magma tend to create large voids - right?

There is a controverse about volatiles on the moon.

What is the reason of these highly porous structures in mare basalt?

Early water?

Lothar