volcanism on mars

By Finlay Evans

Mars is the second smallest planet in the solar system, with a radius of 3,390 kilometres; 53% of Earth’s (Howell, 2014). It is commonly known as the Red Planet, due to its distinctive red colour, caused by the high quantity of iron oxide on its surface (Wolchover, 2012). Mars is home to some of the solar system’s largest volcanoes. One of these is Olympus Mons, the largest known volcano in the solar system at almost 22 kilometres tall, and the second largest known mountain in the solar system (European Space Agency, 2004). But how do we know that they are volcanoes, and why are they bigger than Earth’s?

Olympus Mons has a footprint roughly the size of Poland and was discovered in 1879 by Virginio Schiaparelli. He named it ‘Nix Olympica’, meaning ‘Olympic Snow’ (Sookdeo, 2001), having deduced that it was a large mountain as it was visible even during dust storms. However, he incorrectly assumed that the lighter patches were

Olympus Mons dwarfs Earth’s Mountains By Resident Mario - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=33594059 snow (Krystek, 2014). Mars’volcanoes share a similar formation to those on Earth, but this is not sufficient proof that they formed in the same way. The first chemical evidence for Mars’ volcanism was in the Tissint meteorite (Starr, 2020), which formed on Mars and fell to Earth on July 18th, 2011 (Ibhi, Nachit, & Abia, 2013). Researchers found a type of crystal called olivine in the meteorite. This must have formed in the magma beneath Mars’ lithosphere, the hard outer layer of a terrestrial planet (National Geographic Society, n.d.), and eventually been forced to the surface, causing the temperature to decrease and therefore the crystals to grow. This olivine had irregular bands of phosphorus within it. This is called solute trapping, which occurs when the crystals grow faster than the phosphorus (or any solute) can diffuse out of them, trapping it inside (Starr, 2020). The solute trapping shows that the crystals were growing quickly, so they must have been cooling quickly. Therefore, the crystals

must have been ascending to the surface rapidly, in a magma plume, showing that volcanism existed on Mars at the time of Tissint’s formation, about 580 million years ago (Starr, 2020).

The olivine in the Tissint meteorite has bands of phosphorus, meaning solute trapping has occurred (Taylor, 2012).

But is Mars still volcanically active now? Humans have never recorded a volcanic eruption on Mars, and most scientists previously believed that we never would (Hauber, Brož, Jagert, Jodłowski, & Platz, 2011). However, our estimates for when Mars became inactive have become increasingly more recent, and it is feasible that it could still be active now (Hauber, Brož, Jagert, Jodłowski, & Platz, 2011). The Mars Express orbiter, sent by the European Space Agency and Italian Space Agency (NASA, n.d.), took several images which provided new evidence. An analysis done in 2004 concluded that these images showed lava flows made two million years ago, using data such as the number of impact craters to estimate how long ago a landform was created (Britt, 2004). A separate study done seven years later suggested that they were made within the last 10 million years (Hauber, Brož, Jagert, Jodłowski, & Platz, 2011). Therefore, both studies agree that there is a possibility that Mars is still slightly volcanically active (Hauber, Brož, Jagert, Jodłowski, & Platz, 2011).

Volcanoes on Mars are generally bigger than volcanoes on Earth (UniverSavvy, n.d.). One reason for this is that Mars has a lower gravity, at about 38% of Earth’s (Williams, 2015). Therefore, there is less gravitational pull on Mars’ volcanoes, causing them to compress less (UniverSavvy, n.d.). In fact, Olympus Mons is so big that it would collapse under its own weight if it was on Earth (Starobin & McClare, 2004). The lower gravity also means that bigger volcanoes can keep erupting. When magma goes up inside the volcano, gravity pulls it downwards. Bigger volcanoes require the magma to rise further before the eruption, so it gets increasingly hindered by gravity. On Mars, taller volcanoes can keep erupting and growing for longer, because the weaker gravity allows magma to reach greater heights (CoconutScienceLab, 2018).

There are two main ways that volcanoes can form. One way is that they can form at cracks in a planet’s lithosphere, known as tectonic plate boundaries (Alden, 2021). The plates formed by the cracks are called tectonic plates. Magma can rise through the cracks in the lithosphere from within the planet and cause volcanic eruptions (British Geological Survey, n.d.). The lava ejected from the eruptions then cools to form the shape of a volcano (British Geological Survey, n.d.). This may happen repeatedly, so the volcano grows over time.

Another way a volcano can form is above a hotspot underneath the lithosphere. A hotspot is a stationary area where magma gathers at extremely high temperatures, which can force magma upwards, through a tectonic plate. The lava from this eruption will cool around the centre, forming the volcano (Gutierrez, 2020). Most scientists currently believe that Mars does not have tectonic plates (although some evidence suggests otherwise - see “Further Reading” for details); the lithosphere is all in one piece, meaning that it only has the second type of volcano – formed at hotspots. Mars’ lithosphere does not move in relation to the hotspots, so they remain in the same place under the lithosphere for an extremely long time (Coffey, 2008). Therefore, the

Earth gets volcanic chains due to the movement of tectonic plates, whereas on Mars all the lava dries in the same place, making the mountain much bigger (CoconutScienceLab, 2018).

hotspot keeps adding to the same volcano for a much longer time than on Earth, so the volcano grows much taller. On Earth, the tectonic plates move slowly away from the hotspot, and the hotspot continues forming new volcanoes in a line. An example of this is the Hawaiian Islands, a chain of volcanic islands formed in a row (CoconutScienceLab, 2018)

Map of the Hawaiian Islands, showing how they have formed in a row due to the movement of tectonic plates over a hotspot (Anderson, 2016). There is a lot of debate over whether Mars’ volcanoes are still active, and the subject requires more research. NASA’s recently launched rover, Perseverance (launched on July 30th, 2020) aims to explore the planet’s geology further,

alongside its search for signs of Martian life (Johnson, Hautaluoma, & Agle, 2020) and may provide further insight to the planet’s volcanic history, improving our knowledge of Mars’ past.

Further Reading

To read more about the debate over whether Mars has or once had plate tectonics, please follow this link: https://pubs.geoscienceworld.org/gsa/lithosphere/article/4/4/286/145626/Structural-analysis-of-the-Valles-Marineris-fault (Yin, 2012) References

Alden, A. (2021, February 16). Everything You Need to Know About the Lithosphere. Retrieved February 15, 2022, from ThoughtCo.: https://www.thoughtco.com/lithosphere-in-a-nutshell-1441105 Anderson, D. (2016, October 30). The Speckled Hatchback. Retrieved July 2020, 27, from Blogger: http://thespeckledhatchback. blogspot.com/2016/10/post-80-my-thoughts-on-hawaii-joining.html British Geological Survey. (n.d.). How volcanoes form. Retrieved February 15, 2022, from British Geological Survey: https://www. bgs.ac.uk/discovering-geology/earth-hazards/volcanoes/how-volcanoes-form-2/ Britt, R. R. (2004, December 22). (P. S. Mars Volcanoes Possibly Still Active, Ed.) Retrieved July 31, 2020, from Space.com: https://www. space.com/198-mars-volcanoes-possibly-active-pictures-show.html CoconutScienceLab. (2018, August 29). Why Are Martian Volcanoes So Big? Retrieved July 26, 2020, from YouTube: https://www.youtube.com/watch?v=vuibA3ZpLYg Coffey, J. (2008, June 4). Volcanoes on Mars. Retrieved July 26, 2020, from Universe Today: https:// www.universetoday.com/14837/volcanoes-on-mars/ European Space Agency. (2004, February 1). Olympous Mons - the caldera in closeup. Retrieved February 15, 2022, from The European Space Agency: https://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Olympus_Mons_-_the_caldera_in_close-up Gutierrez, J. J. (2020, January 20). How Does a Volcano Form? Retrieved July 25, 2020, from Owlcation: https://owlcation.com/stem/How-Does-aVolcano-Form Hauber, E., Brož, P., Jagert, F., Jodłowski, P., & Platz, T. (2011, May 17). Very recent and wide‐spread basaltic volcanism on Mars. Retrieved July 31, 2020, from AGU: https://agupubs. onlinelibrary.wiley.com/doi/full/10.1029/2011GL047310Howell, E. (2014, April 21). The Planets in Our Solar System in Order of Size. Retrieved July 22, 2020, from Universe Today: https://www. universetoday.com/36649/planets-in-order-of-size/ Ibhi, A., Nachit, H., & Abia, E. H. (2013). Tissint Meteorite: New Mars Meteorite fall in Morocco. Retrieved July 30, 2020, from CiteSeerX: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.702.3049&rep=rep1&type=pdf n Johnson, A., Hautaluoma, G., & Agle, D. C. (2020, July 31). NASA, ULA Launch Mars 2020 Perseverance Rover Mission to Red Planet. (S. Potter, Editor) Retrieved July 31, 2020, from NASA: https://www.nasa.gov/press-release/nasa-ula-launch-mars2020-perseverance-rover-mission-to-red-planet Krystek, L. (2014). Olympus Mons: The Mega-Volcano. Retrieved July 29, 2020, from Seven Wonders of the Solar System: http:// www.unmuseum.org/7wonders/olympus_mons.htm NASA. (n.d.). Mars Express (ESA). Retrieved July 31, 2020, from NASA Science: https://mars.nasa.gov/mars-exploration/missions/ express/ National Geographic Society. (n.d.). Lithosphere. Retrieved February 15, 2022, from National Geographic Society: https://www. nationalgeographic.org/encyclopedia/lithosphere/ Sookdeo, K. (2001). Altitude of the Highest Point on Mars. Retrieved July 29, 2020, from The Physics Factbook: https://hypertextbook.com/facts/2001/KevinSookdeo.shtml Starobin, M., & McClare, M. (2004, April 22). Sibling Rivalry: A Mars/Earth Comparison. Retrieved July 25, 2020, from NASA. gov: https://www.nasa.gov/vision/earth/environment/Sibling_Rivalry.html Starr, M. (2020, May 12). An Ancient Meteorite Is The First Chemical Evidence of Volcanic Convection on Mars . Retrieved July 30, 2020, from Meteoritics & Planetary Science: https:// www.msn.com/en-au/news/science/an-ancient-meteorite-is-the-first-chemical-evidence-of-volcanic-convection-on-mars/ ar-BB13Wu0i Taylor, J. (2012, January 12). Tissint. Retrieved July 31, 2020, from flickr: https://www.flickr.com/photos/48082563@ N08/6688597931 UniverSavvy. (n.d.). 17 Epic Facts About Olympus Mons: A Large Shield Volcano on Mars. Retrieved July 24, 2020, from UniverSavvy: https://universavvy.com/olympus-mons-volcano-on-mars-facts Williams, M. (2015, December 5). Mars Compared to Earth. Retrieved July 24, 2020, from Universe Today: https://www. universetoday.com/22603/mars-compared-to-earth/ Wolchover, N. (2012, August 8). Why Is Mars Red? Retrieved July 22, 2020, from Space.com: https://www.space.com/16999-marsred-planet.html Yin, A. (2012, August 1). Structural analysis of the Valles Marineris fault zone: Possible evidence for large-scale strike-slip faulting on Mars . Retrieved July 28, 2020, from GeoScienceWorld: https://pubs.geoscienceworld.org/gsa/lithosphere/ article/4/4/286/145626/Structural-analysis-of-the-Valles-Marineris-fault