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PlaidBastard t1_jarlw8t wrote

Many rock types are fundamentally the same -- basalt on the Moon, Earth. Venus, and Mars is all pyroxene, olivine, and plagioclase feldspar. It weathers into different minerals depending on the environmental conditions, so Martian sand is going to be different from Earth sand (unless you pick a weird place on Earth) in some subtle ways, but it's ultimately a pile of little pieces of the same minerals, just with some textural differences and maybe different trace minerals mixed with it.

Earth also has a lot of life and water. You won't find soil in any recognizable form except here. That's a mix of rotting plant matter and what we call regolith, or the powder to gravel sized pulverized rock that all solid planets have some form of at the surface.

So, you'd encounter familiar minerals and rocks making up texturally odd usually super dry sediments in weird contexts, to summarize.

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asteconn t1_jat0l87 wrote

Moon dust for example is incredibly sharp. There are no weathering processes there that would round out the edges.

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agate_ t1_jasl2w2 wrote

The rock types of the inner planets — Mercury through Mars — are basically the same. Earth has more variety because it’s got plate tectonics and water on the surface, but most of the minerals on these worlds are stuff we recognize from Earth, and the major components of the bulk planets are the same.

You mentioned Titan though. The moons of many of the outer planets are largely made of water ice. Out there, water is just a type of rock. (You could argue water is a mineral here on Earth too, especially if you live up north, but if it is it’s a weird one.)

Two other types of “minerals” appear in the outer solar system that are nothing like what we see on Earth. First, many of the outer moons’ surfaces are covered with dark or reddish materials that we can’t identify precisely but seem to be organic carbon compounds of some sort. Second, many of the larger moons have water ice layers so thick that exotic new types of ice form in the high pressure interior.

And in the extreme outer solar system (beyond Neptune), nitrogen becomes a solid ice that could be considered a mineral as well.

Titan in particular has probably has a lot of organic schmoo on top of a water ice crust, a liquid water layer under that a high pressure ice layer under that, and then a core of traditional rocky minerals at the center.

https://openstax.org/books/astronomy-2e/pages/7-2-composition-and-structure-of-planets

https://solarsystem.nasa.gov/moons/saturn-moons/titan/in-depth.amp

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iimplodethings t1_japxr4o wrote

I'm a physicist; you need a geologist or planetary scientist to really answer this. But from my very limited knowledge of planetary geology:

The minerals present on a planet depend a lot on what's going on inside the planet and how it formed. Planets with volcanic activity (e.g. Mars) will have igneous rocks whereas planets without probably won't; some minerals like olivine can be produced inside a planet but may chemically weather to other minerals depending on the atmosphere if there is any. But you find olivine on many planets and in meteorites, and it's the same mineral as the one you find on earth. Also some minerals need water to form - hydrated minerals found on mars can be indicators of past water in that area. Afaik the temperature (in the weather sense, not talking about volcanoes etc) in a region doesn't have much direct impact on minerals but can have a big impact on soils because it affects what life does, and that's the big uncertainty in your question about other planets. The "dirt" on earth is very different in a rainforest than in a desert largely because the rainforest dirt is full of living things and decaying organic matter, but the desert dirt is mostly mineral sand

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mdw t1_javibum wrote

Just one point: Soil is actually of biogenic origin. That means you won't find it anywhere where there's no life to create it. The thing on the surface of terrestrial planets in our Solar system and most moons is properly called regolith.

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