Martian Geology 101

Mt Sharp (Aeolis Mons) is a geologist’s dream. Following on from a recent post, Why Gale Crater, I thought it would be interesting to examine this photo by Curiosity from within Gale Crater, looking at the Mons.

The numbers on this image show the distance from the rover as it looks out across the valley within the crater at Aeolis Mons. The small inset image is of a large rock, roughly the size of the Mars Curiosity Rover, some nine kilometres (roughly 5.5 miles) away, allowing us to gain some perspective on size. The triangular, pointy mound this rock sits in front of is approximately 300 meters (1000 feet) across and 100 meters (300 feet) high.

This image shows sedimentary layers spanning several billion years of history on Mars. Look at the beautifully delineated layers or strata on the Mons. Each layer accumulated over tens to hundreds of millions of years before being eroded away by the Martian weather, leaving the view we see today.

On Earth, we find fossil beds captured chronologically in sedimentary layers that are then exposed by the kind of weathering we see on Mars. That’s not to say we’ll find fossils on Mars, but if life has existed in other Martian epochs, this is where we are most likely to find it.

Not only do geological features on Earth contain fossils, some of them are comprised almost entirely of fossils, like the White Cliffs of Dover. These magnificent cliffs are the fossilized remains of prehistoric single-celled algae which decayed to form chalk a hundred million years ago during the Cretaceous period. At upwards of a hundred meters in height, these cliffs represent the gradual accumulation of sediment over roughly 35 million years.

In Texas, the Capitan mountains in Guadeloupe National Park are another fascinating example of how radically landscapes can change over immense geological time periods.

Somewhat counter-intuitively, this prominent mountain is the remains of a submerged reef dating back to the Permian era, some three hundred million years ago. If these kind of transformations are possible on Earth, imagine what has happened on Mars over the same span of time.

Looking at our image from Curiosity, the 10 kilometre mark on Mount Sharp reveals several contrasting layers, thick dark bands separate several lighter strata, marking vastly different types of rock. This suggests significant differences in the prevailing climatic conditions over millions of years during their formation. Mount Sharp is a time machine, revealing the history of Mars in distinct epochs, showing how the planet has been radically reshaped over time. Mars is anything but static like the Moon. To look at Mars as a cold, dry, dusty, lifeless desert is a gross oversimplification.

One thing NASA will be looking for with Curiosity is graded bedding. If there are several layers of progressively graded rocks, from large to small, then from large to small again, we can be confident these layers were deposited in water at different times, where the coarse stones settle below the fine grains time and again, perhaps during major floods separated by dry periods.

Sedimentary systems are, by definition, built by the flow of material from highlands to low. They are normally carried by liquid, but the wind can play a part as well.

In the case of Mt Sharp, the lowest areas you can see in this photograph are the oldest sedimentary layers, but they’re buried by recent erosion. The higher, relatively more recent layers are still hundreds of millions to billions of years old, as it would take considerable time for all of these layers to have formed, then to have eroded away to reveal the landscape we see today.

Looking at Mount Sharp, it is interesting to note that the layers visible in this image are all parallel, meaning in this local area at least, there has not been any of the tectonic upheaval we see on Earth. Given the lack of a major satellite flexing the Martian crust like Earth’s moon, this is not surprising.

Serious consideration has been given to Valles Marineris, the Grand Canyon of the Solar System, being the result of tectonic activity, but there are no plate boundaries, making this unlikely. There are also theories that describe both the Valles Marineris and the Tharsis Uplift as being the indirect result of the impact that formed the Hellas basin, but that’s a fascinating discussion for another post.

Geology is more than just the study of rocks, it is the study of history on the grandest of scales, and how history has been written into the very rocks of a planet. On Earth, rocks record the chronological impact of life on the planet, perhaps the same is true of Mars. With Curiosity on the ground, Martian geology has been given a whole new impetus. The results of this exploration are sure to be enlightening.

21 thoughts on “Martian Geology 101

  1. Oh, this is so fascinating! There is so much to study on Mars that we can never learn from Earth. I find these differences most interesting, not the similarities.
    Several theories about how Mt. Sharp formed will be formed, several deconstructed, but the most beautiful thing is, we will be able to know about it, not just guess.

    Great post, Peter. 🙂

    • I don’t think most people realize the scope of exploration that’s being undertaken. This is better than landing a rover in the Grand Canyon. There’s sooo much to explore.

    • It certainly is… I suspect we’ll see a slow trickle of discoveries over the next year or so. I’m looking forward to it. And if they fine fossils, well, that’s a game changer.

  2. That top pic looks like the hills of Tatooine from the opening of star wars when R2 is roaming around.

    It is amazing that it looks like such a short trip but those mountains in the distance at 17km away

  3. We gonna find out so much about Mars, yet we know so little about our oceans… and women at that.

    I wonder if we might make a better understanding of our own geology by exploring Mars. We know a lot already, but will it bring more into light? Also, I wonder if Curiosity will last longer than the previous: heheh


    • Oh, love that xkcd cartoon… As for exploring our own oceans, well they’re certainly another world on our doorstep. The exploration of Lake Vostok and Lake Ellsworth may allow us a window into the remote past, with both of these lakes submerged under ice for millions of years. If life has survived down there, it will have followed its own evolutionary path in a pitch-dark environment without photosynthesis and so may well give us insights into the kinds of life that could possibly exist on the moons Europa and Encaledus.

      • Those weird creatures from the dark gives me the creeps. The concept “life finds a way” is awesome, but the “way” is scare to look at. I wonder if we might find something microscopic that was supose to be extinct. Hope it’s something harmful to current life forms. Remember when they found a bacteria that had a different chemical base (can’t remember the element) that is suposed to be poisenous for any life form. MAkes one wonder about how life can vary in different time and space.

        Back on topic, you think we may found out something more about the reason Mars lost it’s atmosphere and magnetic field? Current theories don’t fit on my mind in some way.


      • Good question…

        Mars could never be like Earth, as it’s physically too small, closer in size to the Moon than Earth. Mars was always going to struggle to hold on to a sizeable atmosphere as its escape velocity is relatively low, and without a magnetic field, solar winds strip lighter elements/molecules away. This is one reason why the Martian atmosphere is primarily made up of CO2, as its heavier, and not lost as readily into space
        Comparison between Earth, Moon and Mars
        How did Mars lose its magnetic field? Current thinking is that the northern region of Mars is one giant crater that shocked the planet, disrupting the core, but I don’t find that convincing. There’s a distinct lack of cratering in the north compared to the south, by a factor of 5-to-1. Rather, I suspect the impact in the Hellas basin around 3.8 billion years ago is the real culprit.
        Hellas Impact Basin
        Imagine something considerably smaller than Earth’s moon straying too close to Mars, breaking up and the largest piece slamming into Hellas first, followed by fragments hitting the Argyre Planitia, etc, and you start to see a different picture. The north is probably the virgin planet. While Hellas and its ejecta buried a helluva lot of real estate.

        Have you ever kicked a large, hanging punching bag and noticed the other side bulges out? As the Hellas impact probably caused the Tharsis uplift on the other side of the planet, and the Valles Marineris (the grand canyon of the solar system) is a stress fracture from the same impact. IMHO, this celestial thumping is probably what killed the magnetic core of Mars, the shockwave would have destroyed the planet’s internal dynamo.

        So the question is… could life arise after such a celestial impact? Ironically, the answer is that this impact may have given Mars its best chance of life as the Hellas Basin is sooooo deep the atmospheric pressure is high enough to allow for liquid water and the associated chemical reactions we think are necessary for life. After Gale Crater, onward to Hellas…

        Here’s some more reading on the subject
        Daiy Mail Science Article
        Origin of volcanoes on Mars
        Hellas & associated super craters are antipodal (roughly opposite) the Tharsis Uplift

        Please be aware, however, this not an established theory, so it is speculative.

      • Cool. The same thing that didn’t convinced me didn’t convinced you. That makes better sense and has more evidence to support it. But it must be a hell of impact or one monster sized chunck of rock. I start to thing that crater may be the place where the chunks with building blocks of life here? I mean it’s almost at the same time as life theoretically started to form here, right after the Hadean Era.

        Speaking of life off-topic: on the anime Cowboy BeBop Mars has a massive city with blue sky inside a crater, but I never paid attention as to which crater it was. I’m starting to think it was Hellas due to depth. Maybe our first settlement could be there. Real estate will be expensive, especially if Virgin buys most of it.

      • Yeah… and we see Hellas after roughly four billion years of erosion, collapse and sedimentary build up… there’s a lot of fascinating places on Mars, but Hellas stands out as being exceptional

    • Interesting… I’ve seen some good information on the Hellas impact before, and how it would have led to the formation of the Tharsis uplift, but no details about how this impact would have disrupted the magnetic field so critical to protecting the planet from solar winds. Thanks for the link.

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