The SETI Institute recently tweeted the image below, with the text:

#PPOD: Here is another cool rock at Gale crater on Mars! The spikes are most likely the cemented fillings of ancient fractures in a sedimentary rock. The rest of the rock was made of softer material and was eroded away. @NASA @NASAJPL @Caltech #MSSS fredk, acquired on May 17.

I don't know the size of these features; Curiosity's Mastcam sits about 2.2 meters above the surface but the right and left cameras have different magnifications. Another version of the image can be found here. Since "More Like This" links to "Instrument: MAST_RIGHT" we can guess it's the right camera

Erosion on Mars has a very different history than it does on Earth. But I'm wondering, are there any remotely similar spike-like "cemented fillings of ancient fractures in a sedimentary rock" occurring on Earth? If so, what do they look like and how big are they?

note: A Fulgurite explanation has been deemed not likely since these days the atmosphere can not support lightning powerful enough to create them.

spike-like "cemented fillings of ancient fractures in a sedimentary rock" on Mars from Curiosity rover's MastCam https://twitter.com/SETIInstitute/status/1529832994395004936

  • 1
    $\begingroup$ This could also be similar to something that was discovered by Curiosity. $\endgroup$
    – Fred
    Jun 9, 2022 at 2:13
  • $\begingroup$ @Fred ya that does look like the same kind of "flaky" stuff nearby $\endgroup$
    – uhoh
    Jun 9, 2022 at 4:33
  • $\begingroup$ "these days" seems a bit limiting. $\endgroup$
    – Spencer
    Jun 9, 2022 at 17:52
  • $\begingroup$ @Spencer in what way is who being limited by that? We do know what the atmosphere is like now, we can only make speculative guesses about the weather and lightning billions of years ago. The facts are limiting; my wording is accurate. $\endgroup$
    – uhoh
    Jun 9, 2022 at 18:14

1 Answer 1


Something that comes close are The Pinnacles, near Cervantes in Western Australia. The Pinnacles are a field of rock pillars up to 3.5 m tall.

enter image description here

There are three theories for the formation of the Pinnacles:

The first theory states that they were formed as dissolutional remnants of the Tamala Limestone, i.e. that they formed as a result of a period of extensive solutional weathering (karstification). Focused solution initially formed small solutional depressions, mainly solution pipes, which were progressively enlarged over time, resulting in the pinnacle topography. Some pinnacles represent cemented void infills (microbialites and/or re-deposited sand), which are more resistant to erosion, but dissolution still played the final role in pinnacle development.

A second theory states that they were formed through the preservation of tree casts buried in coastal aeolianites, where roots became groundwater conduits, resulting in the precipitation of indurated (hard) calcrete. Subsequent wind erosion of the aeolianite then exposed the calcrete pillars.

A third proposal suggests that plants played an active role in the creation of the Pinnacles, based on the mechanism that formed smaller "root casts" in other parts of the world. As transpiration drew water through the soil to the roots, nutrients and other dissolved minerals flowed toward the root—a process termed "mass-flow" that can result in the accumulation of nutrients at the surface of the root, if the nutrients arrive in quantities greater than that needed for plant growth. In coastal aeolian sands that consist of large amounts of calcium (derived from marine shells), the movement of water to the roots would drive the flow of calcium to the root surface. This calcium accumulates at high concentrations around the roots and over time is converted into a calcrete. When the roots die, the space occupied by the root is subsequently also filled with a carbonate material derived from the calcium in the former tissue of the roots, and possibly also from water leaching through the structures. Although evidence has been provided for this mechanism in the formation of root casts in South Africa, evidence is still required for its role in the formation of the Pinnacles.


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