“…Digital mapping was performed using an image mosaic base layer consisting of daytime infrared images acquired from the Mars Odyssey Thermal Emission Imaging System (THEMIS) instrument (Christensen et al, 2004), with a spatial resolution of 100 m/pixel (Edwards et al, 2011;Hill et al, 2014). Individual CTX images were used for detailed mapping and analysis due to their relatively high resolution (~6 m/pixel), near-ideal illumination conditions (~3 PM), and excellent coverage of the mapping area.…”
A new mapping-based study of the 900-km-long Mangala Valles outflow system was motivated by the availability of new high-resolution images and continued debates about the roles of water and lava in outflow channels on Mars. This study uses photogeologic analysis, geomorphic surface mapping, cratering statistics, and relative stratigraphy. Results show that Mangala Valles underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian. The occurrence of scoured bedrock at the base of the mapped stratigraphy, in addition to evidence provided by crater retention ages, suggests that fluvial activity preceded the deposition of two of the volcanic units. Crater counts performed at 30 locations throughout the area have allowed us to construct the following timeline: (1) formation of Noachian Highlands and possible initial flooding event(s) before ~1 Ga, (2) emplacement of Tharsis lava flows in the valley from ~700 to 1000 Ma, (3) a megaflooding event at ~700-800 Ma sourced from Mangala Fossa, (4) valley fill by a sequence of lava flows sourced from Mangala Fossa ~400-500 Ma, (5) another megaflooding event from ~400 Ma, (6) a final phase of volcanism sourced from Mangala Fossa ~300-350 Ma, and (7) emplacement of eolian sedimentary deposits in the northern portion of the valley ~300 Ma. These results are consistent with alternating episodes of aqueous flooding and volcanism in the valles. This pattern of geologic activity is similar to that of other outflow systems, such as Kasei Valles, suggesting that there is a recurring, and perhaps coupled, nature of these processes on Mars.
“…Digital mapping was performed using an image mosaic base layer consisting of daytime infrared images acquired from the Mars Odyssey Thermal Emission Imaging System (THEMIS) instrument (Christensen et al, 2004), with a spatial resolution of 100 m/pixel (Edwards et al, 2011;Hill et al, 2014). Individual CTX images were used for detailed mapping and analysis due to their relatively high resolution (~6 m/pixel), near-ideal illumination conditions (~3 PM), and excellent coverage of the mapping area.…”
A new mapping-based study of the 900-km-long Mangala Valles outflow system was motivated by the availability of new high-resolution images and continued debates about the roles of water and lava in outflow channels on Mars. This study uses photogeologic analysis, geomorphic surface mapping, cratering statistics, and relative stratigraphy. Results show that Mangala Valles underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian. The occurrence of scoured bedrock at the base of the mapped stratigraphy, in addition to evidence provided by crater retention ages, suggests that fluvial activity preceded the deposition of two of the volcanic units. Crater counts performed at 30 locations throughout the area have allowed us to construct the following timeline: (1) formation of Noachian Highlands and possible initial flooding event(s) before ~1 Ga, (2) emplacement of Tharsis lava flows in the valley from ~700 to 1000 Ma, (3) a megaflooding event at ~700-800 Ma sourced from Mangala Fossa, (4) valley fill by a sequence of lava flows sourced from Mangala Fossa ~400-500 Ma, (5) another megaflooding event from ~400 Ma, (6) a final phase of volcanism sourced from Mangala Fossa ~300-350 Ma, and (7) emplacement of eolian sedimentary deposits in the northern portion of the valley ~300 Ma. These results are consistent with alternating episodes of aqueous flooding and volcanism in the valles. This pattern of geologic activity is similar to that of other outflow systems, such as Kasei Valles, suggesting that there is a recurring, and perhaps coupled, nature of these processes on Mars.
“…THEMIS observes with both VIS and IR cameras late in the afternoon ($1500 -1700 hrs, when the sun has past transit and doesn't shine as deeply into the candidates). Only the IR camera is used for predawn observations ($0300 -0500 hrs) which are necessary to provide a diurnal range of thermal coverage [Christensen et al, 2004].…”
[1] Seven possible skylight entrances into Martian caves were observed on and around the flanks of Arsia Mons by the Mars Odyssey Thermal Emission Imaging System (THEMIS). Distinct from impact craters, collapse pits or any other surface feature on Mars, these candidates appear to be deep dark holes at visible wavelengths while infrared observations show their thermal behaviors to be consistent with subsurface materials. Diameters range from 100 m to 225 m, and derived minimum depths range between 68 m and 130 m. Most candidates seem directly related to pitcraters, and may have formed in a similar manner with overhanging ceilings that remain intact.
“…Recently, several direct observations of eroded and exposed dikes, including some with unique compositions have been reported on Mars [Shean et al, 2005;Head et al, 2006;Korteniemi et al, 2010;Pedersen et al, 2010;Flahaut et al, 2011]. Here, we report new observations of dikes in Thaumasia Planum (Figure 1a) using imaging and spectral data from THEMIS (Thermal Emission Imaging System) [Christensen et al, 2004], CTX (Context Camera) [Malin et al, 2007], HiRISE (High Resolution Imaging Science Experiment) [McEwen et al, 2007] and CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) [Murchie et al, 2007]. The region in which these dikes occur is characterized by extensive sinuous wrinkle ridges and has been previously mapped as Older Ridged Plains Material (HNr) of Late Noachian to Early Hesperian age [Dohm et al, 2001].…”
[1] We have identified several exposed dikes in Thaumasia Planum Mars using THEMIS, CTX, HiRISE and CRISM data. These dikes extend from tens to $100 kilometers in length with average widths of $50 m. They display classic 'en echelon' patterns while cross-cutting preexisting geologic features, including extensive wrinkle ridges. Both the dikes and associated fissure eruption products have very blocky morphologies with $38% higher thermal inertia than the surrounding regions. The dikes are all enriched in Mgrich olivine relative to surrounding terrain, and a subset also contains elevated high-calcium pyroxene, both of which indicate relatively primitive magma compositions. We propose that these dikes might have served as feeders for the olivine-enriched flood basalts in this region, and may be derived from the Tharsis plume. These observations provide further evidence that the opening of Valles Marineris was facilitated by tectonic stresses following paths of preferential weakness along preexisting structures such as fractures and faults like those indicated by these dikes.
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