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There are some unusual structures in recent images from the Mars Curiosity Rover's MAHLI (Mars Hand Lens Imager) shown in the Space.com article Curiosity Rover Spots Weird Tube-Like Structures on Mars.

An astrobiologist (not at NASA) is quoted as saying that they looked "...remarkably similar to Ordovician trace fossils..." while others are quoted as suggesting that these are visually reminiscent of bioturbation processes on Earth.

Question: What are Ordovician trace fossils and bioturbation, and what do they look like on Earth?


below: NASA's Mars rover Curiosity captured this image on Jan. 2, 2018, with its Mars Hand Lens Imager (MAHLI). Using an onboard focusing process, the robot created this product by merging two to eight images previously taken by MAHLI, which is located on the turret at the end of the rover's robotic arm. Credit: NASA/JPL-Caltech/MSSS

Cropped section are also included for better viewing, in the first one, sunlight can be seen below the structure near the bottom, showing that it extends somewhat upward from the rock below it.

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below: Curiosity Mastcam right image taken on Dec. 15, 2017. Credit: NASA/JPL-Caltech/MSSS

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  • $\begingroup$ Are you asking what is a trace fossil/bioturbation in general or are you specifically interested in Ordovician examples? $\endgroup$ – bon Jan 6 '18 at 10:40
  • $\begingroup$ @bon I don't think it's an either/or situation; a short explanation together with a way to see what they might look like would be ideal. $\endgroup$ – uhoh Jan 6 '18 at 10:51
  • $\begingroup$ My suggestion: do some reading about trace fossils and the science of ichnology, then ask a more pointed question. For some examples, try searching for some common trace fossils like Thalassinoides, Ophiomorpha, or Diplocraterion, all interpreted as burrows. (For what it's worth, my reading is that the 'Ordovician' bit was more of an offhand example than any kind of interpretation.) $\endgroup$ – kwinkunks Jan 6 '18 at 14:29
  • $\begingroup$ @kwinkunks Thanks, but it would take quite a long time to become enough of an expert to be able to find examples that look similar to these on Mars. I've asked this question because there may be people here who have enough knowledge or experience so that after they see these Mars images, they will know much better than I would which examples on Earth look like what these scientists are likely to be thinking of. This kind of experience can't be gained by browsing Wikipedia. I'm not asking that kind of a question. $\endgroup$ – uhoh Jan 6 '18 at 15:50
  • $\begingroup$ Naming the astrobiologist and citing the quote would contribute a lot to the answerability of this question. $\endgroup$ – Spencer Jan 6 '18 at 17:53
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Trace fossils are marks or things left behind by living things do their thing, they are indirect remains of organisms, coprolites (poop), footprints, egg shells, ect. If we found a fossilized beehive or beaver dam those would also be trace fossils. Bioturbation is a specific type of traces fossil, marks of disturbances of the sediment itself animals leave behind, trackways and burrows are the classics.

Identifying bioturbation is tricky in a lot of cases, there are thousands of kinds which makes it worse, there is no way to give a direct answer. Your best bet is to find out what particular bioturbation they are referring to. Burrows, trackways, feeding trails, nest, hold marks the list is endless. there are nearly as many trace fossils as there are organisms that crawl or dig. Worse they are often very contextual and need examination of micro-structure. What is obvious a trace fossil in one formation will look identical to the naked untrained eye to something that is obviously not a trace fossil in a different formation. Generally you want to a specialized experts opinion before if saying something might be bioturbation someplace you don't expect it.

Even from a single location you can have a wide variety of forms, here are a few examples from the ordovician, ...the second of six periods of the Paleozoic Era, 485.4–443.8 million years ago.

Bioturbation

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The photos from mars are not likely to be bioturbation but are almost certainly differential erosion of normal chemical variation in rock. They do not have any of the characteristics that scream "this has to be biological activity" like cross cutting bedding planes or parallel patterns. Sedimentary rocks are rarely homogenous and chemical processes combine with erosional ones can produce some weird results. for comparison here are a few things that are definitely NOT fossils.

**Pseudofossils AKA Leaverite **

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Pseudofossils are things lake look like fossils to the untrained eye but are just rocks, usually the leftovers of a chemical or erosional process. the term leaverite comes from geologists telling others "just leave're there"

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  • $\begingroup$ Thanks for the thorough answer, it's very helpful! $\endgroup$ – uhoh Mar 2 at 4:14

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