Crater Morphometry on the Mafic Floor Unit at Jezero Crater, Mars: Comparisons to a Known Basaltic Lava Plain at the InSight Landing Site

Warner, N.; Schuyler, Andrew J.; Rogers, A. D.; Golombek, M.; Wilson, Sharon A.; Weitz, C.; Williams, Nathan; Calef, F.

doi:10.1029/2020gl089607

Cited by 16 publications

(64 citation statements)

References 54 publications

(138 reference statements)

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“…Crater retention and morphometry on the Cf-fr unit(s) indicate that the rock is resistant (Warner, Schuyler, et al, 2020). Warner, Schuyler, et al (2020) compared their observations from Jezero with the resistant basaltic lava plain at the InSight landing site showing important similarities in crater morphology and time scales of erosion between the units, with one notable difference, the thickness of the regolith, and suggested that the Cf-fr unit is possibly igneous rock.…”

Section: Crater Floor Fractured Roughmentioning

confidence: 99%

“…Craters from the underlying unit are argued to be variably draped and show up as "ghost craters" as the Us gets thicker by Kah et al (2020). Warner, Schuyler, et al (2020), on the other hand, describe these as degraded features resulting from regolith development and aeolian infilling. Increased exposure of Cf-f1/2 unit is shown by CRISM signatures displaying stronger olivine signal and weaker pyroxene signals (Horgan et al, 2020; see also Figure 4a).…”

Section: Undifferentiated Smooth Surface Covermentioning

confidence: 99%

“…Although Us units mapped by Stack et al (2020) generally have uniform textures and tones (at map scale), these deposits were likely not all deposited at the same time, are not comprised of the same material or deposited in the same environment (Stack et al, 2020). Relations observed during detailed mapping suggests that, in all cases, deposition/formation of the Us unit postdates deposition of the rough fractured units (Kah et al, 2020;Stack et al, 2020;Warner, Schuyler, et al, 2020); the stratigraphic relationships among differentiated rough fractured units, however, remains poorly constrained.…”

Section: Introductionmentioning

confidence: 99%

“…Warner, Schuyler, et al (2020b) interpreted the smooth upper subunit of the Cf-fr [corresponding to Us in Stack et al (2020)] in their study area in the center of the crater as a regolith. Crater counting on in the central area of Jezero (Warner, Schuyler, et al, 2020) indicate that the surface is not at equilibrium with surface processes, as 20-70 m craters are being eroded faster than they are produced, and recent work (Quantin-Nataf et al, 2021) highlights spatial variation in the distribution of craters on the floor unit in Jezero, of the sizes that were counted by Shahrzad et al (2019). Quantin-Nataf et al (2021) showed that the youngest crater floor unit has a complex history of cover and later exhumation, complicating interpretation of the crater statistics on the surface.…”

Section: Introductionmentioning

confidence: 99%

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Stratigraphic Relationships in Jezero Crater, Mars: Constraints on the Timing of Fluvial‐Lacustrine Activity From Orbital Observations

et al. 2021

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On February 18, 2021 NASA's Perseverance rover landed in Jezero crater, located at the northwestern edge of the Isidis basin on Mars. The uppermost surface of the present-day crater floor is dominated by a distinct geologic assemblage previously referred to as the dark-toned floor. It consists of a smooth, dark-toned unit overlying and variably covering light-toned, roughly eroded deposits showing evidence of discrete layers. In this study, we investigated the stratigraphic relations between materials that comprise this assemblage, the main western delta deposit, as well as isolated mesas located east of the main delta body that potentially represent delta remnants. A more detailed classification and differentiation of crater floor units in Jezero and determination of their relative ages is vital for the understanding of the geologic evolution of the crater system, and determination of the potential timeline and environments of habitability. We have investigated unit contacts using topographic profiles and DEMs as well as the distribution of small craters and fractures on the youngest portions of the crater floor. Our results indicate that at least some of the deltaic deposition in Jezero postdates emplacement of the uppermost surface of the crater floor assemblage. The inferred age of the floor assemblage can therefore help to constrain the timing of the Jezero fluviolacustrine system, wherein at least some lake activity postdates the age of the uppermost crater floor. We present hypotheses that can be tested by Perseverance and can be used to advance our knowledge of the geologic evolution of the area.

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Section: Crater Floor Fractured Roughmentioning

confidence: 99%

Section: Undifferentiated Smooth Surface Covermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stratigraphic Relationships in Jezero Crater, Mars: Constraints on the Timing of Fluvial‐Lacustrine Activity From Orbital Observations

et al. 2021

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“…There could be a mechanism eroding or reworking the VFU more efficiently closer to the fan and causing it to break down, thereby lowering the TI in this area relative to the center of the crater. Warner et al (2020) suggest that the smooth portion of the VFU may have been less stripped of fine sediments by wind deflation compared to the rough portions, or that the material covering VFU1 and VFU2 has been derived from erosion of the adjacent WFD materials. Ruff (2017) suggested the possibility that the WFD unit could be stratigraphically younger than the VFU, and that the deposits may have been partially eroded away over time.…”

Section: Volcanic Floor Unitmentioning

confidence: 99%

Thermophysical Properties and Surface Heterogeneity of Landing Sites on Mars From Overlapping Thermal Emission Imaging System (THEMIS) Observations

et al. 2021

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Orbitally derived thermal inertia (TI) values of surfaces allow for remote interpretation of rock and sediment physical characteristics. The evolving local times of the Mars Odyssey Thermal Emission Imaging System (THEMIS) mission have enabled surface temperature data collection over multiple seasons and local times over ∼9 Mars years (MY). We utilize this higher temporal resolution data set to separate TI values of individual materials within THEMIS pixels (100 m sampling). In this study, we focus on geologic units within Gusev, Gale, and Jezero crater landing sites to determine their respective TI and ground-truth our methods. We use the KRC model to predict temperatures for a range of homogeneous and two-component thermophysical mixing scenarios (laterally and vertically heterogeneous), and compare those to THEMIS brightness temperatures. The Gusev and Gale crater results are consistent with rover-based evaluations, indurated or clast-covered sands. The best-fit scenarios along the Jezero crater volcanic floor unit show low to moderate TI values representative of coarse sediment, volcaniclastic, or pyroclastic rocks. The light toned unit and western fan deposits both indicate sands and a moderate TI component; we interpret this as heavy fracturing within the rock. Difficulties in modeling some THEMIS temperatures are attributed to daily weather effects, local atmospheric dust variability, and real surface changes over time (e.g., dust deposition and removal); we also observe that some temperature observations lead to non-unique modeled physical solutions. Nevertheless, these methods can still rule out a significant range of material properties and provide meaningful geologic information about Mars' surface.Plain Language Summary Characterizing rock and sediment properties on Mars provides information about its past environmental and surface processes. Thermal inertia (TI) describes how easily materials can be warmed or cooled and can be determined using surface temperatures measured from orbit. TI values are proxies for sediment grain size and rock physical characteristics, which provide clues about Mars' geologic history. The THEMIS instrument, a multispectral thermal infrared camera aboard the Mars Odyssey orbiter, has measured temperatures for 9 Mars years (MY). We have selected three rover landing sites to study with these data. We compare THEMIS temperatures with modeled rock and sediment mixing scenarios. Gusev and Gale crater results agree with rover observations, mixtures of sediment with coarser sediment or lightly cemented rock. A volcanic unit in Jezero crater appears to have formed from volcanic sediments or bubbly lavas. The light toned unit in Jezero is consistent with a brokenup rocky surface covered with sand, and the western fan is dominated by sand-sized sediment. Clouds, dust, and frosts complicate models of THEMIS temperatures. Sometimes, the same temperatures arise from multiple rock/sediment mixing scenarios; this complicates interpretation. However, the methods in this study narrow down ...

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Degradation at the InSight Landing Site, Homestead Hollow, Mars: Constraints from Rock Heights and Shapes

Wilson

Golombek

Trussell

et al. 2021

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Rock heights and three-dimensional shapes around the InSight lander in Homestead hollow, Mars, provide new constraints on modification of the degraded 27 m in diameter impact crater and are a tool for characterizing degradation on regolith-covered lava plains on Mars. Decreasing average rock height and increasing percentage of fragments where height comprises the short axis from outside to within the hollow supports significant ejecta deflation accompanied by infilling of the interior. Rock relief outside the hollow is compared with expectations of pristine ejecta thickness and indicates up to~40 cm of near-rim early deflation (decreasing to a few cm out to one diameter) can account for the predicted eolian component of infilling and that other eolian infilling sources are not required. Scattered rocks in the hollow are ejecta from subsequent nearby impacts and their mostly buried expression is consistent with subsequent longterm degradation estimated to be 10 -4 m/Myr. Basalt rock shapes at InSight are likely similar to basalt rock shapes on Earth, but appear more platy, bladed, and elongate in a triangular form factor plot and more discoidal and bladed in an axes ratio plot. Nevertheless, addition of 10 cm to near rim rock heights to account for continued partial embedding in ejecta would result in rock shapes quite similar to terrestrial rocks. Consistency between degradation estimates based on current rock relief and rock shape after accounting for partial embedding in ejecta indicates up to~30-40 cm early (~0.1 Ga) near-rim deflation was followed by much lesser long-term degradation. Key PointsRock heights and shapes at Homestead hollow indicate early transport of deflated ejecta sediments can account for infilling of the crater.Near-rim rock heights and shapes relative to the expected original versus remnant ejecta thickness indicates~40 cm deflation occurred.

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Crater Morphometry on the Mafic Floor Unit at Jezero Crater, Mars: Comparisons to a Known Basaltic Lava Plain at the InSight Landing Site

Cited by 16 publications

References 54 publications

Stratigraphic Relationships in Jezero Crater, Mars: Constraints on the Timing of Fluvial‐Lacustrine Activity From Orbital Observations

Stratigraphic Relationships in Jezero Crater, Mars: Constraints on the Timing of Fluvial‐Lacustrine Activity From Orbital Observations

Thermophysical Properties and Surface Heterogeneity of Landing Sites on Mars From Overlapping Thermal Emission Imaging System (THEMIS) Observations

Degradation at the InSight Landing Site, Homestead Hollow, Mars: Constraints from Rock Heights and Shapes

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