月球和地球的尘土在显微镜下有什么不同的特点?What are the differences between lunar dust and Earth dust under the microscope and how it behaves?


As posed, your question is meaningless, as “Earth dust” could mean anything from clay to talcum power to cat dander.


Let’s rephrase the question to ask what you really mean to ask: Why do boots leave clear prints in lunar regolith when boot prints in most Earth soils would collapse without moisture to stick the particles together.


First let’s only discuss sand, as it’s the best example we have of Earth soil that won’t hold a print when dry, and because most other Earth soils contain organic matter that make a comparison essentially meaningless.


Here are fresh shoe or boot prints in dry Earth sand:


Notice you can see individual grains of sand. That’s because on Earth, there is wind and water, and any time weathering sand particles get below a certain size, the resulting dust blows or is washed away and winds up going into solution forming sediment somewhere and/or chemically reacting with some surface.


That means that natural sand on Earth has a fairly consistent grain size, with few larger or smaller particles. It also means that Earth sand is essentially a bunch of little silica balls:


[Libyan desert sand—particle size 500–1,000 microns]


See all those rounded edges? Those come from constant movement of particles against each other, either by the action of wind or waves.


On the moon, there is no wind and no waves. Moon dust is created by the constant bombardment, over millions of years, of surface rocks by meteorites large and small. Unlike Earth, there is no wind to carry away dust, and no water to cause it to bind chemically. It just builds up, giving the regolith a fractal symmetry of boulders large and small.


[Lunar regolith from Apollo 17, particle size 20–50 microns]


Lunar dust is much, much smaller than Earth sand, and see all those jagged edges? They readily lock particles together. Further, on the moon there is no air between the particles, either to lubricate or “fluff” them. There is just dust, settled by millions of years of impacts and moonquakes, and tightly locked together.


Here is Buzz Aldrin’s boot print on the moon:

这是Buzz Aldrin在月球上的靴子印记:

Note how fine the dust is inside the compressed print. The undisturbed surface appears rougher because it’s made up of ejecta paticles of all sizes that have fallen after meteoritic impacts, leaving a “fluffy surface.”


The closest thing you can find to lunar regolith on Earth is rock dust from a mechanical crusher that has not had the opportunity to weather.


Portland cement is a good example, and behaves similarly.


[Clear shovel imprint in pile of dry portland cement.]

Lunar regolith has a finer grain size even than cement, and it is electrically charged, which further helps particles stick together. This is very different from sand or other Earth soils, which generally contain more volatiles and organics, and at least some moisture.


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