• Justin@lemmy.dbzer0.com
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    9 hours ago

    Aren’t the layers in the rock showing that water was definitely present on Mars, and that they’re formed by sediment being deposited and forming into sedementary rock over time?

    • TheDudeV2@lemmy.ca
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      32 minutes ago

      I’m not a geologist but I’ve read up on it a fair bit.

      This Mars photo appears to be sandstone.

      On earth sandstone is usually associated with ancient rivers, lake shores, and sea shores. But also sand dune fields.

      The thing with sandstone though, is it’s not just sand. Rather, it’s sand plus time plus pressure plus cementation.

      Now, the time part is obvious. What’s sandstone now was sand a long ass time ago (usually).

      Pressure? That’s a little harder to understand for me here. Has mars ever had tectonic stuff going on to bury it (and hence have pressure applied), followed by erosion and uplift? Or am I incorrect and pressure is not a necessary condition? Maybe sandstone without pressure is a thing it’s just weaker and/or less dense? Maybe layers of volcanic basalt or something could have a similar effect? I don’t know and would love to have someone more knowledgeable fill this part out.

      Cementation? This part, I’m nearly certain, REQUIRES water. On earth anyway, this happens when ground water absorbs chemicals from other rock/stuff (for example carbonates from sea shells, but there’s lots of other chemicals that can do this), then flows through the beds of buried sand, and some of those chemicals are deposited along with magical chemistry stuff happening, and your sand becomes sand stone.

      So I don’t 100% know that the short answer to your question is “yes”, but I’m leaning towards a solid “yeah, probably, but I’m not a real geologist and Mars isn’t a real Earth so I dunno”.

    • j4k3@lemmy.world
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      9 hours ago

      I could be wrong, but I don’t think so in this case. Water would likely create more variation in banding where some groupings of layers is present and distinct. What I see in the differences at higher levels appears to be from exposure to wind and solar temperature fluctuations due to exposure. It looks too linear from top to bottom. With water I expect those more distinct sections of banding like you see on the Earth pic side. Maybe there was a lot more or less rain for a time due to a mountain range that came and went, or a local sea or large water basin. Those layers are deep time and more like the slow accumulation of an average dust before wind patterns shift significantly or some event shifts the composition like exposure of a different large rock unit to winds regionally. It is hard for humans to grasp deep time like this.

    • scala
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      9 hours ago

      Think so. That’s what I came here to ask

  • umbrella
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    8 hours ago

    i wonder if humanoid aliens would be a common thing throughout the universe

    like a mass effect sorta thing