Fire and Ice on the Red Planet – A photogeologic study of Malea Planum to assess volcano-ice interactions and their potential to provide habitable environments on ancient Mars
Final Report Abstract
The unique paterae and late Noachian wrinkle-ridged plains of the Malea Planum region (MPR) encompass ~1.2 million km2 and occupy a ~1000 km wide gap in the southern rim of the Hellas basin. Being key to Mars’ early volcanic, tectonic, and climate evolution, this project included a comprehensive and in-depth photogeological investigation of the MPR using multiple datasets including THEMIS-IR (100 m/px) as a basemap (2.2 x 10^6 km2 quadrangle size; scale 1:1,000,000) and deriving apparent model ages based on crater size-frequency distribution measurements on suitable areas. Along with stratigraphic, morphologic, hyperspectral, and gravimetric analyses, as well as findings by previous works in the surrounding regions, our chronostratigraphy resulted in a complete landscape formation model of the mapping area. At 3.9-3.8 Ga, Malea and Pityusa Paterae form, probably as volcanic collapse calderas geographically controlled by Hellas-concentric faults. Surprisingly, Pityusa Patera turned out to host folded, layered deposits, possibly pyroclastics emplaced during patera formation. Based on structural analyses, the shortening and extent of these deposits indicate Pityusa Patera to be a funnel-type caldera over a magma chamber at 57.5 to 69 km depth, i.e. potentially at the crust-mantle interface. Around 3.8-3.7 Ga, up to ~3.9 million km³ of volcanic and clastic/ballistic deposits partially sourced by Pityusa/Malea Patera activity and/or by now-obscured vents are emplaced and now prevent the analyses of any volcanic flow features that might be associated with these paterae. Shortly after, the deposits are isotropically shortened, likely by global contraction, thereby forming the wrinkle-ridged plains of the MPR. Simplistically assuming the wrinkle-ridged plains to entirely consist of basaltic deposits with ~2 wt% H2O, outgassing might have produced ~0.8 m global equivalence layer of water and/or 3.9 mbar of H2, which could have temporarily increased ambient temperatures, potentially enabling fluvial and lacustrine processes across the Malea-Hellas regions. After plains emplacement, doming above a shallow magma chamber and its subsequent partial evacuation forms Amphitrites Patera as a caldera on a ~1.5 km high, broad rise collocated with a positive ~260 mGal free-air, but no significant Bouguer gravity anomaly. Between 3.7 and 3.6 Ga, the northern slope of Amphitrites Patera is heavily dissected by low-viscosity flow processes that drain towards the Hellas basin floor and form the Axius Valles amongst others. Based on feasibility studies and in contrast to a previously suggested catastrophic groundwater sapping event, we favor glacial meltwater/mud or alternatively low-viscosity lavas sourced from Amphitrites’ summit to have formed the Axius Valles. 1,777 km long Mad Vallis, which was traced three times further south than in previous works, along with other smaller channels traversing the entire MPR and connecting the South Pole area with the Hellas basin are also formed around this time. After this, Barnard crater is formed, whose walls and floor surprisingly host sinuous valleys and ridges, likely formed by meltwater from ice sheets that might also have occupied Amphitrites Patera. Around 3.5 Ga, approximately 80-140 m (i.e., up to ~140,000 km³) of layered, friable materials are emplaced across large parts of the MPR, surprisingly as far north as 60°S. These materials turned out to be an extension of the circum-south polar Dorsa Argentea Formation (DAF) and possibly originated as lag deposits from wet-based glaciation with entrained pyroclastic materials, potentially sourced from volcanic activity at Peneus Patera, which might have formed around the same time. Combining structural analyses with a funnel-type caldera model similar to Pityusa Patera would imply collapse of a magma chamber at 19.5 to 26 km depth, i.e., potentially in the mid-crust. After volcanic activity subsided, over 200,000 km³ of friable airfall deposits are laid down in two distinct phases, each leaving behind a pedestal crater population as erosional remnants. Recent erosion of pyroclastics entrained in DAF deposits across the MPR potentially supplies the late Amazonian formation of vast, mostly transversal and barchanoid dune fields in local depressions throughout the MPR and Noachis Terra to the northwest, thereby challenging previous theories of more local supplies. In conclusion, our in-depth investigation of the MPR, which included a comprehensive map and chronostratigraphic as well as morphometric analyses, shows that the area hosts a complex volcanic, tectonic, as well as most likely (glacio-)fluvial history and acted as corridor between the south polar area and the Hellas basin. Activity related to Amphitrites and Peneus Paterae likely contributed to ridged plains formation and the associated volatile release as well as mobilization had significant environmental effects on the southern hemisphere. Moreover, we suggest Pityusa Patera to be one of the oldest, extant volcanic landforms on Mars and one of the largest calderas in the solar system, which makes the folded, likely mantle-derived, deposits on its floor a prime target for future exploration.
Publications
- (2019). Malea Planum: Timing and Scale of Deposition and Erosion on the Oldest of Mars’ Large Volcanic Provinces. In Lunar and Planetary Science Conference (p. 1435)
Bernhardt, H., Williams, D. A., Clark, J. D.
- Photogeologic Mapping of Malea Planum: A New View of the Oldest of Mars’ Large Volcanic Provinces. In Annual Meeting of Planetary Geologic Mappers (p. 7014)
Bernhardt, H., & Williams, D. A.
- (2020). An overview of explosive volcanism on Mars. Journal of Volcanology and Geothermal Research, 409
Brož, P., Bernhardt, H., Conway, S. J., & Parekh, R.
(See online at https://doi.org/10.1016/j.jvolgeores.2020.107125) - (2020). Geomorphologic and Structural Mapping of Pityusa Patera indicates Formation as Funnel-type Caldera above Magma Chamber at Crust-Mantle Boundary. In Annual Meeting of Planetary Geologic Mappers (p. 7015)
Bernhardt, H., Williams, D. A., Klimczak, C.
- (2020). Water and lava both seem viable for the formation of one of Mars’ densest and largest channel networks. In Lunar and Planetary Science Conference (p. 1088)
Bernhardt, H., Williams, D. A.
(See online at https://doi.org/10.5194/epsc2020-19) - (2021). Geology and history of the Malea Planum region: A new view of Mars’ oldest large volcanic province. Icarus, 366, 114518
Bernhardt, H., & Williams, D. A.
(See online at https://doi.org/10.1016/j.icarus.2021.114518) - (2021). Pityusa Patera, Mars: Structural analyses suggest a mega-caldera above a magma chamber at the crust-mantle interface. Geology, 1–5
Bernhardt, H., & Williams, D. A.
(See online at https://doi.org/10.1130/G48903.1)
