• leftzero@lemmynsfw.com
      1·
      3 months ago

      Those particular rocks seem to be sandstone, though… which would pretty much be proof of liquid water having existed at some point.

      Rocks are rocks, sure… but rocks tell stories, and these ones are telling a story that, while common and somewhat uninteresting on Earth, is quite interesting indeed when told on Mars.

      • Yokozuna@lemmy.world
        1·
        3 months ago

        You are totally right. I was going to make a big post about how they actually formed but I deleted it halfway through. These rocks are definitely significant in that the same processes on earth happen on Mars so we can infer how they were deposited and formed. Hence my shitty first comment, rocks are rocks.

  • choss@sh.itjust.works
    1·
    3 months ago

    Mmmm that’s some good choss! Do you happen to know where the photo on the right was taken? My geoguessr brain wants to put a pin on Kanab, Utah

  • Justin@lemmy.dbzer0.comEnglish
    0·
    3 months 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
      0·
      3 months 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”.

      • Naz@sh.itjust.works
        0·
        3 months ago

        There’s a non zero chance that Mars is a remnant of the planetary impact that occured to the Earth ~ 3.5 BYA. The issue is that’s a really loose hypothesis, but the speculation is that Theia - which impacted Gaia (old Earth) was an ice planet / water world, which gave us most of our oceans.

        Evidence of water evaporation on Mars therefore makes sense, as a catastrophic effect (such as planetary impact) would indeed cause the atmosphere to boil off, leaving behind these dry lakes and riverbeds.

        I personally haven’t spent enough time on Mars to make a substantial conclusion, there wasn’t enough time to do any science between the sheer insanity of basic survival on a planet that seems uniquely designed to kill you and crush your spirit before doing so.

        I totally approve of your analysis however, and it’s proof why geologists deserve a seat on the interstellar jumpships :3

            • Zron@lemmy.world
              1·
              3 months ago

              I think the fact that it’s really far away, in a circular orbit, and doesn’t have a big chunk missing is still a good sign that mars isn’t theia

              • notfromhere@lemmy.ml
                1·
                3 months ago

                Why would it have a chunk missing after all this time? If it did could we even tell? Whatever it was isn’t still in the area so being far away may not mean much. Circular orbit is probably biggest reason it’s likely not Mars, although it could have evened out relatively recently.

                This simulation shows the Mars sized object merging with Earth so there goes that theory.

    • Danquebec@sh.itjust.works
      0·
      3 months ago

      That’s how I figured which was which (I don’t have the ability to quickly figure out left from right like most people have, so that left me time to play at guessing).