Regolith
[4][5][6] The American geologist George P. Merrill first defined the term in 1897, writing: In places this covering is made up of material originating through rock-weathering or plant growth in situ.
[15] The presence of regolith is one of the important factors for most life, since few plants can grow on or within solid rock and animals would be unable to burrow or build shelter without loose material.
[18][19] The regolith is also an important source of construction material, including sand, gravel, crushed stone, lime, and gypsum.
Regolith covers almost the entire lunar surface, bedrock protruding only on very steep-sided crater walls and the occasional lava channel.
This regolith has formed over the last 4.6 billion years from the impact of large and small meteoroids, from the steady bombardment of micrometeoroids and from solar and galactic charged particles breaking down surface rocks.
The impact of micrometeoroids, sometimes travelling faster than 96,000 km/h (60,000 mph), generates enough heat to melt or partially vaporize dust particles.
This melting and refreezing welds particles together into glassy, jagged-edged agglutinates,[21] reminiscent of tektites found on Earth.
[22] Below this true regolith is a region of blocky and fractured bedrock created by larger impacts, which is often referred to as the "megaregolith".
During the early phases of the Apollo Moon landing program, Thomas Gold of Cornell University and part of President's Science Advisory Committee raised a concern that the thick dust layer at the top of the regolith would not support the weight of the lunar module and that the module might sink beneath the surface.
However, Joseph Veverka (also of Cornell) pointed out that Gold had miscalculated the depth of the overlying dust,[24] which was only a couple of centimeters thick.
The sand is believed to move only slowly in the Martian winds due to the very low density of the atmosphere in the present epoch.
It is believed that large quantities of water and carbon dioxide ices remain frozen within the regolith in the equatorial parts of Mars and on its surface at higher latitudes.
