Post contributed by Dr. Eng. Bartosz Pieterek, Adam Mickiewicz University in Poznań and Polish Geological Institute – National Research Institute.
Despite the fact that the Martian surface has been intensively studied for several decades, we still do not fully understand the evolution of the Red Planet. Specifically, our insight into the compositional evolution of Martian magmas is limited, as most volcanic regions were modified or even buried by younger volcanic activity or other geological processes. But luckily not everywhere. By using high-resolution images provided by the Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE), on board the Mars Reconnaissance Orbiter, coupled with their stereo-pair digital elevation models, we identified a group of small, kilometer-sized volcanoes in the Claritas Fossae region (examples in Image 1, full area in Image 2). These volcanoes are emplaced on an old and heavily fractured terrain that survived younger volcanic resurfacing event(s). The studied volcanoes, which do not show significant modification by erosion and therefore cannot be very old, show a composition that is different from most other young volcanoes and lava flows found elsewhere on Mars.
Image 1: Examples of studied volcanic edifices with their structural and stratigraphic relationships with the fractured terrain of the Thaumasia and Claritas Fossae regions. (a)The most common type of volcanic edifice occurringin Claritas Fossae. Based on cross-cutting relationships with the older fractured terrain, the volcanic activity has to be younger than the fracturing. This example has been produced using CTX image G17_024955_1524, centered at 27.3983°S and 255.0633°E. (b) This image presents an interesting example of two volcanic edifices separated by a cliff attributed to faulting, which were likely supplied by the same subsurface dike. On Earth, similar-looking edifices may be formed due to the small difference in elevation between vents as evidenced by the Fagradalsfjall eruption (Phase 2; April 2021) in Iceland (Barsotti et al., 2023). This view was produced using CTX image P18_008156_1516, centered at 28.2575°S, and 254.6175°E. All images are available in NASA’s PDS system.
Previous studies aimed at deciphering the evolution of Claritas Fossae focused on large-scale regional structures noting that the volcano-tectonic activity ceased at around 3.5 Ga, whereas small-scale structures were not considered. Now, a detailed mapping campaign revealed that kilometer-sized volcanic edifices occur on both sides of the main Claritas Fossae fault that divides the studied region into the large Thaumasia Graben in the west (Hauber and Kronberg, 2005) and the Claritas Fossae highlands in the east (Image 2). In general, most of the studied edifices are characterized by elongated to irregular or, more rarely, circular outlines and relatively steep-appearing flanks. The detailed morphology of these edifices varies as some reveal central fissures (Image 2), central ridges (Image 1), or central summits (Image 3). However, the observed morphologies, in general, share similarities with terrestrial volcanoes.
Image 2: The location of the studied volcanic field of the Claritas Fossae region. The Mars globe shows the location of Claritas Fossae in the regional context of the Tharsis volcanic province. (a) This panel shows the regional map of the studied region with a clear division between western lowlands and eastern highlands. (b) The lower panel shows the particular study area subjected to mapping. The basemap is produced using the CTX images overlaid by the MOLA – MEX HRSC Blended global digital elevation model (spatial resolution of 200 m/px). The yellow stars and blue triangles pinpoint the locations of the volcanoes presented in Images 1 & 3. The inset presents the example of two fresh-looking volcanoes that are emplaced on the old fractured terrain of the Claritas Fossae region.
Although most of the studied edifices are not associated with flow-like units, in one case a central conical-shaped edifice surrounded by a caldera-like rim or collapse scar and irregular lobate flows has been identified (Image 3). The structure and morphological parameters of the cone together with the irregular flows show similarities to terrestrial composite volcanoes (Image 3) suggesting the co-occurrence of effusive and explosive eruptions.
The studied volcanoes are associated with rocks that are rich in low-calcium pyroxenes, instead of high-calcium pyroxenes which are frequently associated with volcanic products emplaced in the Amazonian (< 3 Ga) epoch (Mustard et al., 2005; Poulet et al., 2009). Previously, rocks enriched in low-calcium pyroxenes were observed in association with the oldest known areas of Mars only, like in the ancient cratered terrains in central peaks of large impact craters, on their crater rims, or in isolated massifs. However, as the Claritas Fossae edifices appear to be little eroded, they are likely not ancient. Therefore, such composition is unexpected in association with volcanoes, as it contradicts previous observed relations between pyroxene composition and age. Hence, Claritas Fossae represents a promising area where we can study how Martian volcanism evolved over time and as a result, get better insight into the thermal conditions within the upper Martian mantle where the magma forming these edifices was generated.
Altogether, the compilation of morphological studies with spectral observations highlights the need for further research searching for small-scale volcanic edifices on Mars that might still provide undiscovered insights into the Martian endogenic processes.
Image 3: A comparison of studied edifices with their terrestrial counterparts. (a) An elongated edifice with a central ridge at the summit (CTX image P18_007945_1532, centered at 26.89°S, 255.27°E). (b) Corresponding terrestrial construct of the Callaqui volcano in the Andes (Chile). The photo is adapted after Melnick et al. (2006). (c) Schematic drawing showing the simplified map explaining the formation of the nested central cone surrounded by the elevated caldera-like rim. The central circular edifice is highlighted by smooth slopes compared to the surrounding terrains and the flow unit originated from the northern slope. CTX image B22_018098_1519, centered at 28.2°S, 260.23°E. (d) Three stages of development of the depicted nested cone in the plan-map view with the magma source as feeder dike that is depicted in the cross-section. (e) Terrestrial example of the post-caldera edifice (Anak Krakatau volcano; first emerged from the sea in 1929) with the submarine caldera that was formed after the Krakatau eruption in 1883. The caldera rim is highlighted by three truncated islands. The bathymetry data were downloaded from the GMRT database. (f) Photo of the Anak Krakatau volcano that is volcanically active with well-distinguishable volcanic features. Image credit: Volcanological Survey of Indonesia.
Further reading:
Brož, P., Bernhardt, H., Conway, S.J., Parekh, R., 2021. An overview of explosive volcanism on Mars. J. Volcanol. Geotherm. Res. 409, 107125.
Brož, P., Čadek, O., Hauber, E., Rossi, A.P., 2015. Scoria cones on Mars: detailed investigation of morphometry based on high-resolution digital elevation models. J. Geophys. Res. Planets 120, 1512–1527.
Hauber, E., Kronberg, P., 2005. The large Thaumasia graben on Mars: is it a rift? J. Geophys. Res. Planets 110, 1–13.
Mustard, J.F., Poulet, F., Gendrin, A., Bibring, J., Langevin, Y., Gondet, B., Mangold, N., 2005. Olivine and pyroxene diversity in the crust of Mars. Science 307, 1594–1598.
Pieterek, B., Brož, P., Hauber, E., Stephan, K., 2023. Insight from the Noachian-aged fractured crust to the volcanic evolution of Mars: a case study from the Thaumasia graben and Claritas Fossae. Icarus, 407, 115770.
Pieterek, B., Laban, M., Ciążela, J., Muszyński, A., 2022. Explosive volcanism in Noctis fossae on Mars. Icarus 375, 114851.
Poulet, F., Mangold, N., Platevoet, B., Bardintzeff, J.M., Sautter, V., Mustard, J.F., Bibring, J.P., Pinet, P., Langevin, Y., Gondet, B., Al´eon-Toppani, A., 2009. Quantitative compositional analysis of martian mafic regions using the MEx/OMEGA reflectance data. 2. Petrological implications. Icarus 201, 84–101.
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