Complex geology of two large impact craters in Tyrrhena Terra, Mars: Detailed analysis using MEX HRSC camera data

Abstract

Tyrrhena Terra, located just north of the roughly 200 km Hellas impact basin, is a typical region of the ancient cratered southern highlands on Mars. Its base material is a mixture of Hellas ejecta, prebasin remnants, and highland terrain, all later saturated with smaller (<200 km) impact craters. Fluvial and lacustrine deposits, erosion, tectonic movements, volcanic materials and aeolian processes have subsequently modified the region further. In this study we take a closer look at two adjacent unnamed craters in Tyrrhena Terra, located at 24.5°S, 80.8°E (crater “A”) and 23.9°S, 79.3°E (crater “B”). The craters are covered by the ∼20–80 m/pixel Mars Express High Resolution Stereo Color imager (HRSC) multispectral data, which together with MOC, THEMIS, and MOLA data sets allows us to make very detailed analysis of the area. We describe several identified geological and geomorphological units with their individual characteristics (e.g., morphology, color, cratering records, and elevation differences) and interpret their individual evolution. The crater floors show several unique material types of both depositional and erosional origin. Crater A has a large 200 m high central massif and a central peak ring as well as a unique low‐lying terrain type, “honeycomb terrain,” with narrow 50–200 m high ridges and intervening pits. Additionally, both craters exhibit erosional features similar to each other and nearby craters, indicating episodes of deposition of various material types in both craters. We find that the crater pair reveals many characteristics which are typical of the N Hellas rim but are not found elsewhere.

Simulating the development of Martian highland landscapes through the interaction of impact cratering, fluvial erosion, and variable hydrologic forcing

“…12c). A few craters, particularly on the eastern rim of the major Hellas basin, exhibit pronounced central depressions surrounded by broad plains sloping inward from the crater rim (Korteniemi et al, 2005;Moore and Howard, 2005b) (e.g., Fig. 13).…”

Geomorphic and stratigraphic analysis of Crater Terby and layered deposits north of Hellas basin, Mars

“…(b) The informally designated craters A (D = 95 km, lower right) and B (D = 83 km, upper left) of Korteniemi et al [2005a] from subframe of HSRC rectified nadir image H0389 (elevation‐cued in color version online; see Figure 1 for context). Inset shows simplified version of the geologic map from Korteniemi et al [2005a] using their unit classification terminology. Layered deposits in crater B have experienced little postdeposition erosion and extend to a higher elevation near the northeast crater wall.…”

“…High‐resolution images and data from the Mars Exploration Rovers and several orbiting instruments including the Mars Orbiter Camera (MOC), the Thermal Emission Imaging System (THEMIS), the High Resolution Imaging Science Experiment (HiRISE) and the Mars Express Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) visible‐near‐infrared hyperspectral imager permit detailed observation and interpretation of layered deposits on Mars that may have been deposited in water‐rich environments [e.g., Malin et al , 1998; Christensen et al , 2003; Squyres et al , 2004; Gendrin et al , 2005; Bibring et al , 2006]. Several craters surrounding the Hellas impact basin (Figure 1), including Crater Terby, have been filled with layered deposits [ Moore and Howard , 2005b; Korteniemi et al , 2005a, 2005b].…”

“…Numerous craters around the Hellas basin, marked with black and white circles, contain interior layered deposits [after Moore and Howard , 2005b]. Layered deposits discussed in the text are located in Craters Terby (“T”), Millochau (“M”) [ Mest and Crown , 2005], “A” and “B” from Korteniemi et al [2005a], Niesten (“N”) and the informally named SW crater (“S”). This MOLA shaded relief map of the Hellas region is in Lambert Conformal projection and covers the region from 25°E to 115°E between 15°S and 60°S.…”

Minimum estimates of the amount and timing of gases released into the martian atmosphere from volcanic eruptions

“…First, it is not clear which valley networks were included in their slope analysis, and mapping valley networks from imagery data alone has proven to be a subjective exercise (Luo and Stepinski, 2006;Molloy and Stepinski, 2007;Hynek et al, 2008). Ejecta from the Hellas impact basis has also been proposed to explain the topographic highs in this area (e.g., Korteniemi et al, 2005), and in the Phillips et al (2001) model the slope of pre-existing topography north of Hellas would have only been accentuated. The most obvious argument against this interpretation, however, comes from the geology of the Tharsis-rise itself.…”