Footstep in the lunar regolith. Image credit: NASA
Regolith is the blanket of soil, broken rocks, dust, and other tiny objects that cover some celestial bodies like the Earth, Moon, asteroids, and other planets and natural satellites.
On Earth, the presence of regolith – in this case, soil – is essential for the survival of various organisms. It’s where the plants grow and insects and small animals dwell. It is also used as a basic construction material. Earth regolith comes from weathering of rocks and from biological processes.
On asteroids and natural satellites like the Moon, regoliths mostly come from debris of asteroid or meteoroid impacts. The absence of an atmosphere on these celestial bodies make them highly vulnerable to even the smallest meteoroids. On Earth, tiny meteoroids vaporize even before reaching the ground so regolith formation due to such impacts is not as common.
Footstep in the lunar regolith. Image credit: NASA
During impact with the lunar surface, micrometeoroids are able to generate heat that melt or partially vaporize dust particles. When the bi-products refreeze, they form glass-like material called agglutinates. Underneath the finer lunar regolith is a bedrock known as the megaregolith.
On Mars, the regolith there is like rust colored-talcum powder. This reddish dust is so fine, that some of it that gets blown by the occasional dust storms remain in the atmosphere to add to the planet’s red color.
Although, nowadays, the sand barely gets carried away by the winds on Mars, it is believed that the presence of flowing water in the past may have caused the formations of the martian regolith. There is reason to believe that frozen water may still lie underneath the martian soil.
As mentioned earlier, regolith on asteroids come about just like those on moons. That is, they are caused by impacts. The NEAR Shoemaker, a spacecraft that landed on the near-Earth asteroid Eros, was able to capture images of the regolith found there. It is currently the best collection of images featuring regolith on an asteroid.
Here are links to those images:
Eros regolith
Eros surface1
Eros surface2
Universe Today also has its own collection of articles mentioning regoliths. Here are two of them:
Here are two episodes at Astronomy Cast that you might want to check out as well:
Large Scale Structure of the Universe
Infrared Astronomy
Reference:
NASA
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